Hey guys. I read through the whole debugging page, but I'm still completely lost. I'll get right to it: I'm not building my own BSIAB II, although I might if it turns out I somehow irreparably damaged the circuitboard on my Brownie. If I do have to rebuild it from scratch, I guess I'm in the right place.
I changed the transistors in my Brownie to NTE457's, the local electronics store equivalent of a 2N5457. I put these in Q4 and Q5.
It was working great. No problems and playing a lot over several days. Perfect.
Today, I had some sockets come in. I figured it'd make changing transistors easier...nope. I ended up taking them out, and soldering the transistors back in the normal way. I think I just clipped the legs off the sockets and soldered the legs of the transistors right onto those...I know, lazy.
I worried that I might've applied too much heat to the board while I was doing all this as I wasn't being quick or sharp with the soldering iron. However, I checked carefully and I do not have any solder bridges. The points on the back of the board are all clean. On the top of the board where the components are, there's probably more solder than there needs to be, but the joints are solid and there are no bridges either.
Now I'm having some issues. Very, very low volume. It seems barely at unity with all the knobs dimed.
I have no idea how to test transistors. But I tried. I just set my multimeter to Ohms, and found that testing the two outside legs of each transistor gave the same readings either way. I read that this is what they're supposed to do. The readings on all the transistors varied a lot, but on each one, it was the same reading whether I had the black or red probe on either of the outside legs of the transistor.
However, on Q4, in one direction I'm getting a really high reading, more than twice as high as all the other transistors (like 1200 ohms or something), and when I reverse it, it gives me a negative reading, around -300 ohms.
This is the only diagnostic criteria I have, if it can qualify as diagnostic criteria. The ONLY other mod I did was put a 100v .0010mf capacitor in place of where one of the .0022 capacitors used to be. I can't imagine that affected anything. I even tried clipping it just in case, but that proved to not affect anything.
I tried replacing the transistor, thinking maybe I just accidentally damaged that one. Put the old original transistor back in, it worked like a charm, and I thought I had it!
...until about 30 seconds into playing it, it started crackling a bit, and then the volume dropped. Back to the same very low volume it was at when I initially ran into the problem. And the reading on the transistor is doing the exact same thing (it was doing it before and after things went wrong again).
So...
1) Weird reading on Q4 transistor (others seem "normal" as far as I know)
2) Replacing the Q4 transistor worked, but only for a very short time before crackling/cutting out, and then finally settling at a very, very low volume.
It sounds okay with all the knobs dimed. So in a sense it still works. But obviously this is not how I want to use the pedal, and something is very wrong.
Any ideas?
Scratch that...with the knobs dimed, it gradually started losing more and more volume. Went from being louder than unity to quieter than unity to fizzling out to almost nothing.
I'll repeat: only mods I attempted were changing the transistors, removing one tone cap and replacing one tone cap. No issues previously, but today ran into major problems.
Given that, is it possible I just fried the circuitboard somehow while trying to change the transistors? I looked at all the adjacent components and I didn't hit anything with the soldering iron except for a little fraying on the blue plastic of the trimpot where the iron hit it lightly. Transistors were working just fine for several days with zero issues, but attempting to put the sockets in today, removing them, then putting the transistor back in....was never the same after it.
I have a hard time believing I was so heavy handed with the iron that I fried the board, but is something like that possible?
I just got excited, re-touched every joint for the transistor, and it was working great...but then, AGAIN, after about 30 seconds, major volume drop, losing gain, fizzling out. And the transistor is still having that weird reading where it's negative resistance on one orientation, and really high resistance on the other orientation (black probe touching left leg in one case, black probe touching right leg in the other).
Welcome.
Don't "touch" joints. LOOK at them. SEE the solder has wetted both/all leads.
Since it was OK, and you tinkered, and now it is not-OK, odds are that you made a good joint bad "somehow". It happens. A lot.
Quote from: PRR on February 26, 2018, 10:16:42 PM
Welcome.
Don't "touch" joints. LOOK at them. SEE the solder has wetted both/all leads.
Since it was OK, and you tinkered, and now it is not-OK, odds are that you made a good joint bad "somehow". It happens. A lot.
I'm gonna try wicking out all the solder so I can put the legs through the holes in the PCB and solder them properly. I didn't do that the first time and it was okay but maybe it'll help.
I'll redo it the best I can. If it'll help I'll put some pictures up of the solder job for any critique.
I think your in the right place. Good thing Paul got here first before I could say "reflow, reflow, reflow". Follow his advice and use your eyes before you start hitting the problem areas with more heat.
If you can't see any obvious cold solder joints or shorts I'd hit it with an audio probe if you have one. Cheap and easy to put one together and not much more of a ball ache to use than a multimeter.
What a day!
I spent today removing the 3 transistors I plan on replacing, and thoroughly cleaning out the eyelets/through-holes. My new transistors (MPF102) have not arrived yet. I plan on using all MPF102's and running it at 18v, which means pulling the 3 J201's originally in Q3, Q4 and Q5.
What a nightmare. No matter what I tried, I couldn't seem to wick the solder out of the through-holes. I don't have any braid at the moment, but I do have plenty of stranded wire, so I just made my own. A little flux, stranded wire...it got all the excess off the PCB around the through-holes, but it couldn't get the solder out of the middle.
I even ran it through the holes carefully with some pliers while the solder was molten, and even that didn't manage to wick all the solder out. I would pull the wire out and the hole would still be plugged with solder.
I damaged one of the through-holes in an attempt to push a remnant leg of a transistor that I cut off...with a .030" guitar string. I used a bit too much force at the wrong angle, and off came part of the eyelet. The flanged part...about half of it. On the bottom of the PCB. The shaft going through the middle seems to be entirely in tact and on top where the transistor mounts it looks OK. But boy was I kicking myself after that. I pushed forward nonetheless.
I'm hoping that it will still function but if I have to repair that, I guess I'll have to learn that too. That was a bit of a forceful method, although it worked beautifully on the first 6 through-holes. I was gentler on those and only gently pushed the .030" string through the hole, and even found that with the addition of flux, the string was acting as a solder wick. When I got to Q3 I was overconfident, and that's when I damaged the eyelet. I pushed way too hard trying to force the string to eject the transistor leg remnant and residual solder plugging the hole, but I guess I was actually pushing on the flange of the eyelet. And off it came.
After all this? I had an epiphany. One that I wished I'd had earlier. A straw.
I simply heated up the through-hole/eyelets, one at a time, and forcefully blew through a straw when the solder was molten. Worked like a charm. Held the PCB up to good lighting, and could see light coming clear through all the through-holes. Finally.
The parts are so light, even if a long leg of a transistor/cap/etc. was left in the through-hole, I think this straw method would have worked just fine. I did check and made sure that no beads of solder that came off when I blew on the eyelets contacted anything else. It was such a trivial amount of solder that I could hardly find any of the pieces that blew off anyway. They were at the bottom of the metal case of the pedal.
So now I have open holes ready to accept my 3 new transistors that are on the way....I'm just hoping I don't have to replace the eyelet or do some other repair in order to get this thing to work.
The whole endeavor took well over several hours...and then I realized the power of the straw. I was about to go into the garage and try using compressed air, and then I was just like, "Wait a second..."
I'll have to look up how to make (and use) an audio probe. I have so much to learn.
I am determined to get this pedal working, though. Thanks for the replies, guys, and I will keep you posted on my progress. With any luck I'll be able to get this thing working and then record a video (with decent audio) demoing the mods to the pedal.
Good luck with it! A solder sucker would be a safer alternative to a straw. That molten solder you're blowing through the hole could go anywhere and cause shorts (or worse still, splashback in your face).
An audio probe is basically half a guitar cable, solder a capacitor and Croc clip to one end and plug the other end into your amp. Croc clip to ground, use the cap to touch the pads on the pcb and listen. Follow the signal path and listen for where it gets weaker or lost altogether.. The hard bit is strumming the guitar while you do this. I tend to lay it in the floor and use my foot.
http://www.diystompboxes.com/wiki/index.php?title=Debugging (http://www.diystompboxes.com/wiki/index.php?title=Debugging)
Section two on this page should have you covered if you go ahead and build one.
Would you recommend any solder suckers in particular or does it not make a difference what brand/quality you get?
So...success! Kind of. The volume is sounding fine now. I put J113 transistors in place of all the old ones, except the Q1 and Q2 MPF102's. I have some MPF102's coming in the mail and I might try those now that I'm more confident in swapping parts.
Only thing is that when I have the gain turned all the way up, and a little less, it feeds back. It does this even when the guitar volume is completely rolled off.
Any ideas what that could be? I'm able to get rid of this "howling" by adjusting the bias with the internal trimpot. Just curious what that means, and if that's a normal occurrence.
Anyway, just in time for band practice! I'm not sure how I feel about the J113's yet. I am definitely a fan of clipping one .0022uF cap, and replacing the other one with a .0010uF. When I had MPF102's in Q1 and Q2, then NTE457's in Q4 and Q5, and a J201 in Q3, I quite liked the sound, and might end up going back to that.
I feel much better now that I'm not worried that I'll ruin the circuit board by experimenting (carefully).
Scratch that....whole thing just cut out again. Not sure what happened. Seemed to be working fine. Sounded perfect. Then the volume dropped off again. And just standalone, it seems to be making an intermittent popping sound.
This time, it seemed to happen after kicking on a Fuzz Face. Could this possibly do anything to create issues, stacking pedals like that? I wouldn't think so...just seems I have the same issue as before, where the pedal is functioning fine for a while, then drops off.
Either way, that's the pattern...it works fine, everything sounds great and does what I'd expect it to do...then after a few minutes of being on, it just craps out. Loses all volume and gain and is about 5% as loud as it's supposed to be.
Any thoughts? I'll get around to making that audio probe as soon as I can. But if anyone has an idea what this kind of problem could be indicative of....just seems very strange.
Since I only messed around with the transistors I figure the problem has to be there...but I'm fearing that I damaged the board, as the solder job on the transistors looks perfectly fine to me. Can't understand what would cause it to work perfect for several minutes, but then splutter out seemingly out of nowhere.
All right guys! I didn't make an audio probe yet, but I used my multimeter to test the transistors, per the Debugging page recommendations.
I'm very new to all this, but I know transistors have Drain, Source, and Gate legs...and that *all* of them are supposed to have some kind of voltage.
I found that in Q2, Q3, and Q4, the topmost leg on each was reading out at 0 volts. I simply held the black probe from my multimeter on the ground tab of one of the jacks, and used the red probe to touch each leg of each transistor.
I went over the PCB and cleaned up any stray bits of solder. No solder was bridging anything, but I cleaned up any flecks on the PCB regardless.
I also put some electrical tape over each pot, as I suspected that they might be touching points on the PCB when the nuts are threaded on. They do seem very close to the PCB. So electrical tape to insulate them, just in case.
Then I re-flowed not only each of the offending legs reading 0.0 volts, but also the leads going to the jacks on the PCB. I forgot that I didn't know I could simply bend the pots out of the way to access the PCB to solder, and had tried to desolder the pots from the PCB. Only a couple spots looked a little anemic, but I added some more solder to those to fill them out.
Also, by fiddling around with the board so much, the wire for 9v power going to the PCB fell off, and so did one of the leads connecting the input jack and the PCB. I re-soldered those on generously and got as good and strong a joint as I could afford.
By some miracle, I tested again, and it worked.
Put a 9v battery in the clip and probed the transistors again. This time, *each and every leg* was getting a voltage reading. None of the legs on any of the transistors were reading out at 0 volts. Previously, when I was having the "fading out" volume and gain issue, I was getting wonky readings on some of the transistors. Now, while I have no idea what the voltage readings mean, I can see that each leg of each transistor has voltage.
I suppose that's a good thing :)
I was still getting a "howling" feeding back with the gain and treble all the way up. At first I adjusted the trimpot to re-bias, and that fixed it. I simply turned the trimpot with the guitar plugged in and the pedal on, and listened until the howling went away.
Then I had a thought. There are two .0022uF caps on the circuit. Why not try moving the .001uF cap to the other position? I remembered reading something where someone said that the .0010uF cap worked best on *one* of the two positions for those tone caps.
I don't understand it, but when I moved the .0010uF cap from one point on the PCB to the next, and left the other location empty...it worked perfectly. I was then able to re-bias with the trimpot and with the gain and tone all the way up, there was NO howling noise anywhere, no matter where I biased it.
I played for about 30 minutes just now. Stacked with OCD, and my Fuzz Face, and, *knock on wood*....no issues. Sounds AMAZING.
I've also decided that even though I have MPF102 transistors coming in, this project scared me too much! I will save those transistors for a potential BSIAB II build from scratch. I would love to make one of those myself, as these are great sounding pedals...and then I can try the mods shared by people in this community, without risking ruining my Brownie that I paid a good chunk of change for.
I'll play some more tomorrow. I hope it's safe to say that if my pedal works perfectly for a few hours of continuous running, it should be good to go. Maybe I can put a clip up of the mods I did and how they sound.
Thanks for the help, guys. I do have a DS-1 lying around that is broken, and while I've been learning, I might as well try to fix that one while I'm at it. I'm keen on making an audio probe and seeing if I can build up some experience with working on guitar effect PCBs.
Thanks again! 3AM over here and I can finally sleep now that my Brownie is working :p My Fulltone OCD isn't the only OCD in my house right now....lol.
Quote from: Slight Return on March 01, 2018, 03:12:48 AM
Put a 9v battery in the clip and probed the transistors again.
Does the famous debugging thread not say to connect a battery? The clue is in asking for the battery voltage right at the beginning. No volts in = no volts out. ;D
Quote
I suppose that's a good thing :)
"A learning opportunity." Initiation complete. ;)
Idk why I mentioned the 9v battery like that...I did use one from the beginning, otherwise no current! I followed the instructions from the very beginning, starting with testing the battery to make sure it had some juice in it, then snapped it onto the battery clip in the pedal and started testing the transistor leads.
I'm feeling great after getting the Brownie up and running. I like it a lot more with the lower gain transistors. I do have a broken DS-1 pedal that my friend left over here that might turn into a little project. It is not working at all. Someone plugged an 18v power supply into it and it fried it. Blew the diode which I'm assuming is there to protect the board from exactly what happened to it.
An audio probe seems like the perfect tool for the broken DS-1. I'm excited to get one going and see if I can figure out what's wrong with that thing, and get it working again.
It would be nice to be able to learn on something that I don't care about. I have a lot invested in the Brownie and especially it being a brand new pedal for me, the stress of having it not functioning was a bit much for me to deal with.
But man! What a harrowing experience. I guess the areas that were originally getting 0 volts were just cold solder joints. Maybe I just did them too quickly for fear of causing damage. Dabbing a little flux on each terminal and then holding the iron against them for several seconds seems to have woken things up.
I did not touch Q1 and Q2 to my knowledge, but since Q2 was getting 0 volts on one leg as well, I decided to re-flow the joint there too, just in case. And it did look like it could use it.
Amazing how many issues a simple cold joint can cause.
Initiation complete indeed :)
it be a bit late now to ask, but can you please post at least a link to the circuit you are working from/to, the board layout as well, if you like, and some photos of the board you have built, including the off-board parts? besides we just like to look, there might be "some things" that we can see might help you on your next build.
I guess not too late...played again today and it's blatty and weird sounding. Horrible.
I get home to try it out, and now it is not working at all. All it's doing is very loud crackling when I turn the pedal on, and no other sound at all. Kill me -__-
http://guitarpedalbuilders.blogspot.com/2012/06/bsiab-2-ii-brown-sound-in-box-2.html
There's the schematic...as I understand the CMATMOD Brownie is a licensed BSIAB II. So the schematic should be the same. FYI, I have *no* idea, not even a tiny one, about how to read a schematic. I've got a ton of homework to do with that.
I changed transistors Q3, Q4, and Q5, replacing them (for the time being) with J113's instead of J201's that were originally in there. I also put a .0010uF cap in place of the original .0022uF cap. You can see it in the picture below...it's the green capacitor, the only green one on the board. It looks quite out of place :p
My only intention was to change those transistors and then the cap, that's it...so I'm still running into problems and not sure why.
(https://s14.postimg.org/nl25tr6kd/20180301_042939.jpg) (https://postimg.org/image/nl25tr6kd/)
Update. Hopefully this info will be helpful for anyone who can potentially help me with saving this pedal.
http://www.generalguitargadgets.com/pdf/ggg_bsiab2_instruct.pdf
According to that picture, the BSIAB II should have about the following voltages:
Q1:
Gate.......0v
Source....0.95v
Drain......4.5v
Q2:
Gate.......3.8v
Source....4.5v
Drain......8.0v
Q3:
Gate.......0.3v
Source....0.75v
Drain......4.3v
Q4:
Gate.......3.8v
Source....4.3v
Drain......8.0v
Q5:
Gate.......0.5v
Source....0.9v
Drain......3.4v
I just hooked a 9v battery up to my pedal, put a jack in the input, turned it on, and tested each transistor with my multimeter. Black probe went on the ground from the jack, and used the red on each individual leg of the transistor. Hopefully I'm doing this right. My 9v battery is reading out at 7.7v. I am running the pedal for playing use with an 18 volt isolated power supply, FWIW. Here's what I got:
Q1:
Gate.......0v
Source....2.01v
Drain......5.08v
Q2:
Gate.......2.26v
Source....5.06v
Drain......6.7v
Q3:
Gate.......0.1v
Source....0.99v
Drain......4.11v
Q4:
Gate.......2.2v
Source....4.1v
Drain......6.66v
Q5:
Gate.......0.1v
Source....0.81v
Drain......0.85v
Made an audio probe just now. I assemble and wind my own custom pickups, and I had an old extra one lying around, so I had a thought:
Just wire the pickup directly to a Switchcraft jack, and play music on my phone next to the pickup to get consistent audio while I'm free to probe with the other hand. I had two spare Switchcraft jacks hanging around so I just wired everything to those and plugged the jacks right in.
Seems to be working very well and is extremely compact, and my other hand is free to probe while the music from my phone plays next to the pickup. It only has to be next to it, not on top of it.
(https://s14.postimg.org/jkzlv95h9/28429670_190914271668733_2941059446702342144_n.jpg) (https://postimg.org/image/jkzlv95h9/)
I only had a .018uF cap lying around. I'll try to get a 0.1uF cap tomorrow.
I've been probing around, and this method does work, from what I can tell...but I don't know what I'm looking for. Should EVERY leg of EVERY single component on the board produce clear sound, just with different tones?
Because I have quite a few spots that sound either extremely distorted and messed up and awful, or are making no noise at all. Is the general idea to look at the schematic and simply follow the board from beginning to end, and your problem is indicated by the very first component that you find "failure" with?
I need to know what "failure" means to determine anything from this test. Some resistors I probed made it sound very good...very clear, clean, just like an amplified version of what my phone was playing. Other ones distort, as I'd expect, but other points make no noise at all, like some of the legs of the transistors.
The probe makes sense to me now. I'm quite happy with this method. I'd take a pic of the whole setup with the phone and all, but....I need my phone to take pictures.
OK guys. Hopefully this will help. I really need help here and am at a huge loss. I edited this in Paint to highlight what I've traced with the probe so far, and where I ran into my first component that I think might not work.
TL;DR: I started probing at the Input. The first resistor legs both get audio and are the first connections after Input. One of these resistors gets no audio on one of the legs. That resistor is connected to a capacitor, and the capacitor is getting no audio signal either. The other resistor that works goes to Q1. That resistor and Q1 get audio on all legs. Q1 Drain connects to Q2 source. Q2 Gate and Source get audio. Q2 Drain has no signal. The transistors that Q2 Drain lead to also have no signal on any of their legs.
(https://s14.postimg.org/703q5jc7h/messed_up.jpg) (https://postimg.org/image/703q5jc7h/)
From your voltages;
Get a new 9V battery. Then have a very close look at Q5. You may have a short between the Source and the Drain legs of the transistor or that transistor is faulty.
It is possible that when you soldered it in some solder wicked up the legs and caused a short.
Quote from: Slowpoke101 on March 02, 2018, 12:49:02 AM
From your voltages;
Get a new 9V battery. Then have a very close look at Q5. You may have a short between the Source and the Drain legs of the transistor or that transistor is faulty.
It is possible that when you soldered it in some solder wicked up the legs and caused a short.
(https://s14.postimg.org/oq5er0krx/28429319_1836615899964414_5094418811826733056_n.jpg) (https://postimg.org/image/oq5er0krx/)
Image on the right is the old transistor. Soldered a new one in, and that one is on the left in the picture.
I just clipped the legs off the old one and soldered this one down, without cleaning the through-holes and inserting the new transistor. I tried my best to be careful not to solder too far up the legs or to bridge solder between them.
Checked with audio probe...nothing. Checked with voltmeter: same exact readings as before. Does anything look blatantly wrong with the way Q5 is soldered on? I know I left the legs quite long but I just wanted to see if a new transistor would change anything...apparently not.
From probing, I did discover issues earlier in the circuit. If the signal is getting cut off somehow very early in the circuit, namely at one of the first resistors after the Input, and at Q2, then naturally the later transistors will not be getting the full power they need, correct?
It looks to be soldered OK, no problems that I could see. However, is there a reason for using J113 FETs? The circuit is really intended to use J201 or 2N5457 types - if you can find real ones. Good ones are getting very rare.
From personal experience I found that the 2N5457 FETs work very well in the BSIAB II. The effect may not work very well with J113s.
Back to Q5 for a moment. The trimpot is initially used to set the Q5 Drain voltage to 4.5 volts, it is further adjusted for best sound when the effect is working. Generally set it to 4.5 volts and then forget about it. Measure the voltages on all 3 pins of the trimpot. One pin will be close to the voltage of the battery and the other two (which are connected) should be adjustable.
When probing with your audio probe you should find an amplified signal (which will distort the further along you go through the circuit) on Q1 Drain (Q2 Source), Q3 Drain (Q4 Source) and then Q5 Drain (greatly amplified compared to the input signal). The signal should then go off to the tone and volume circuits.
See what you find.
**EDIT: I really should mention that the 4.5 volt setting must be done with the battery (or power supply) running at 9 volts. It is meant to be set at half the supply voltage otherwise Q5 will not be biased correctly.
Just tested the resistor that was getting no signal on one leg with the audio probe. The multimeter does nothing when testing it. When I put it into resistance mode the screen just reads "1," and when I touch that resistor, it stays at "1."
I tested every other resistor in the circuit. My results are in the picture. A total of 3 resistors on the entire circuit get a readout. The rest, the MM just stays at "1" and does nothing.
I'll let the pic speak for itself. I don't have a schematic yet and while BSIAB II seems close, my Brownie has more capacitors and resistors in the circuit than are listed in the BSIAB II schematic, so I have reason to believe it's different.
I don't know what any of this means, but not getting a signal or readout can't be good.
(https://s14.postimg.org/7kncm6cvx/resistors_test.jpg) (https://postimg.org/image/7kncm6cvx/)
@ Slowpoke
Just read your message as I was about to post this one.
I did break off half the flange of one of the eyelet through-holes. That was on Q3, I think on the Drain leg connection. On the back of the circuit board. It broke when I was attempting to push the molten solder out of the hole with a guitar string. The central shaft going through the board looked to be in tact. I was going to replace the eyelet until I realized how difficult that might be. I found this website and I wonder if I should give it a try:
http://pinballrehab.com/1-articles/solid-state-repair/board-rework-test/230-repairing-plated-through-holes
NOTE: The issues started not when I tried J113's, and not even when I broke the flange on the through-hole on Q3, but when I attempted to solder in sockets for the NTE457 transistors in Q4 and Q5. That is when the issues started. At the time, I hadn't even removed Q3 yet. I got the sockets soldered in, but when I tested them with the transistors loaded, it didn't work. I removed the sockets, but ever since then, I have been having major issues with the Brownie.
Moving on...
I read that J113's are close to MPF102's, and since they're still being made I figured I'd have a better shot trying them than NOS. My Brownie came stock with MPF102's in Q1 and Q2, and then J201's for the rest. I'd read somewhere that the guy who designed it thought that when it's run at 18v, it sounds "best" with all MPF102's. So I went for as close an equivalent as I could find after researching online.
I should've just left it with the two NTE457's in Q4 and Q5. I tried that originally and had zero issues, and very much liked the sound...MPF102's in Q1 and Q2, NTE457's in Q4 and Q5, and a J201 in Q3. I simply thought I wouldn't have any issues experimenting with different transistors, and then this whole debacle happened. The pedal is crackling, squealing, cutting in and out and doing all kinds of weird stuff. I thought it was working fine, but I had it cranked today and noticed a myriad of problems, on top of sounding like garbage.
A true nightmare, especially as I don't have a lot of money and investing in a Brownie hurt my wallet pretty badly!
I was not happy with the sound out of the box, but now I wonder if I would've been just as happy with the stock transistors, and simply clipping one of the .0022uF capacitors to open up the treble a bit. That was the most immediate difference I noticed, even more so than the lower gain transistors. Even still, I found that if I only used 1 capacitor, it DID matter what position I had it in, so even if I end up getting another Brownie eventually, I'm scared that I'll ruin it by clipping one of the caps.
I do have some 2N5458's coming in the mail. I read that those are close enough to 2N5457 to be interchangeable. At this point I'm having a hard time imagining that I didn't completely butcher this thing.
Thank you for the advice. I'll try that tomorrow. I'll report back with my findings. I haven't tried testing with the trimpot yet. I had just set everything by ear initially. I'm assuming no damage can be done by adjusting the trimpot with reckless abandon? As that's what I did when trying to set it up, and I have no idea what I left it on for a while.
I did find that Q2 Drain has no output. No audio signal coming through when probed. Q1 has output on Gate, Source, and Drain, although Source is almost inaudible on Q1. Audible but noticeably weaker and much quieter than Gate and Drain. Q2 has output on Gate and Source but *nothing* on Drain. And all the other transistors after that have no response to the audio probe either, on any of the legs.
That was right at the start of the circuit, after a couple resistors following the Input. One resistor went to Q1, the other resistor to a capacitor...the resistor going to Q1 got audio on both legs, but the other resistor, only on one. As far as the audio probe revealed, the problems start extremely early in the circuit after the Input, no audio signal coming from one of the resistors *directly after the Input* being Culprit #1.
I can see on your built board two caps look like they are tantalums, the two 1uF's. please check you have them in the right way, as they are usually marked for (+) leg whereas aluminium electros usually mark (-) leg.
looking on the ggg circuit dia, any part that connects to ground or +9V will have no signal on that leg. the other end of those components I think will all show signal, to some degree (obviously except for the LED string).
Is there any way to tell which way to orient the tantalum caps? They are oriented in opposite directions to each other. Only one has a + marking directly next to the circle it's mounted on (the tantalum cap next to the trim pot). The other + sign is not directly adjacent to the other tantalum cap, and it appears to be intended for another component.
I would just try reversing the other one to the same orientation as the tantalum cap next to the trim pot, but I'm unsure of this. Is it safe to experiment with that or if I get it wrong could it short something out?
If you look carefully at the solder pads that the tantalums are solder to you will see that one pad is square and the other is round. The square pad is the positive connection. If you look at the tantalums closely you will see a value and polarity marking. This polarity marking marks the positive lead which is the opposite of the markings on an electrolytic capacitor where the negative lead is usually the one that is marked.....Usually.
***Edit: I am aware that I just basically repeated D_A's advice (apologies) but I have found lately that people are having trouble with determining what the polarity of a tantalum capacitor is. It is not obvious and can be difficult to see. If you are building something or repairing something that needs a tantalum installed, the positive leg on a new tantalum is usually longer than the negative leg....assuming that the legs haven't already been trimmed.
Anyway, any progress on checking the trimpot and where the voltage for Q5's Drain has gotten to?
Quote from: Slowpoke101 on March 02, 2018, 04:18:09 PM
If you look carefully at the solder pads that the tantalums are solder to you will see that one pad is square and the other is round. The square pad is the positive connection. If you look at the tantalums closely you will see a value and polarity marking. This polarity marking marks the positive lead which is the opposite of the markings on an electrolytic capacitor where the negative lead is usually the one that is marked.....Usually.
***Edit: I am aware that I just basically repeated D_A's advice (apologies) but I have found lately that people are having trouble with determining what the polarity of a tantalum capacitor is. It is not obvious and can be difficult to see. If you are building something or repairing something that needs a tantalum installed, the positive leg on a new tantalum is usually longer than the negative leg....assuming that the legs haven't already been trimmed.
Anyway, any progress on checking the trimpot and where the voltage for Q5's Drain has gotten to?
Thanks so much for the advice. I really appreciate it.
I plugged the pedal into my board with the 18v power supply powered on. Black leg of multimeter to ground, red leg to Drain of Q5. The reading seemed to be correct. I was able to adjust the trimpot so the Drain leg of Q5 read at 9.14, while it was hooked up to the 18v power supply. Half of the supply voltage is the goal, correct?
All I did different from yesterday was this: The set of 2N5458 transistors I ordered came in the mail today. I just put them in. I left one of the original MPF102's in Q1...then from Q2 to the end, 2N5458. I got rid of all the J113's. Only reason I didn't use MPF102 in Q2 as well as Q1 is because I stupidly clipped the legs off *very short* to try out a J113, as when I probed it the other night and it was getting no sound, I thought maybe the transistor was bad. Kind of upset now, as the MPF102's in Q1 and Q2 are what I originally wanted to try.
When my replacement MPF102's come in I suppose I could give those a whirl. I'm a bit gun-shy after this whole fiasco although perhaps it was as simple as not using the right transistors.
J113's are listed as "This device is designed for low level analog switching, sample and hold circuits and chopper stabilized amplifiers." I am not sure what that means but perhaps they're simply incompatible with this circuit.
Maybe the J113's were causing a problem? I'm not saying my pedal is fixed. I sure hope so, but I am only in the cursory stages of testing it with the new transistors.
But I am getting more signals now with the audio probe, and the Drain leg voltage seems to be perfectly in spec. Running at 18v, the trimpot seemed perfectly adjustable and being able to get the Drain to ~9v sure is a good sign. To be fair, I forgot about the trimpot advice before I swapped the transistors...so I did not test the Drain with the trimpot with the J113's in there.
All I did was get rid of the J113's, put in 2N5458's, and now the pedal seems to be working without issue.
I will keep in mind that things seemed to be OK with the NTE457 transistors, but then things went wrong while I was still using those transistors. I don't trust I'm out of the woods yet. But these definitely seem to fit better.
I'm feeling tempted, if this pedal continues to work, to just buy one of the BSIAB II kits and try to make one from scratch if I would like to further tweak the tone. I have some MPF102 transistors coming in the mail as well that I planned on experimenting with.
I could build a brand new circuit board from scratch, put sockets in for the transistors, and all that good stuff. And try some of the other mods listed on this community that sound very cool, but I would not want to risk doing to my Brownie given what's already happened so far.
If the pedal is now working that's great :icon_biggrin:
Adjusting the trimpot to half (ish) the supply voltage is the initial setting. As long as the pedal is working you now adjust the trimpot setting "by ear"...Adjust it to where you find it sounding the best according to your tastes.
Getting a kit would be a good idea just for the fun value and being able to leave this pedal alone until you feel more confident with modifying it.
Sometimes when you buy components (particularly FETs) the component can be faulty or below specifications. This can make things very difficult to work out what is going on. For a newcomer to the craft this can be a very bad experience. You may have received some below spec' FETs which won't work in this circuit but may work in others.
Testing components is not difficult but can be confusing. There are many helpful articles on this site (and elsewhere) that can help with this. A case in point is your own resistance measurements. You were able to measure only three resistors. All those resistors were under 1K (1000 Ohms) which means that your multimeter was not set to the correct range(s) to be able to measure the other resistors. Spend some time with your multimeter and learn its ways because a multimeter can be one of the most useful pieces of test equipment that you can have.
Hopefully you have repaired your pedal and now you can get on with playing without any problems.
I definitely need to learn how to use the multimeter. So it wasn't that they had no reading...I was just using the meter incorrectly.
I can understand DCV at "20" for testing voltages that will be around 0-20. Simple enough. When I tested the Drain leg of Q5, I was able to understand that I needed to set the meter to DCV and in the numerical range of what I expected to find.
For pickups, I understand to use 20k as I'm looking for the resistance of the wire, and up to 20k range, ex. 6.2k, 12k, etc. That's about as deep as my understanding of multimeters goes at the moment.
Fortunately, my friend left a busted DS-1 at my house months ago. I replaced the battery clip and blown diode but the pedal still doesn't work. I'm excited to use the audio probe I made to test it out. I do think it's a convenient method too, using one of the spare pickups I made and my cell phone to play music into it while I probe...seems to work very well.
And I was pleased to find that I am getting a signal from the pedal. It was overloaded with more voltage than it could handle, the diode blew, and the battery clip was also bulging out. So it seems the pedal has some major issues, and I also noticed a solder bridge on a couple components on the back.
But it could be a great project to help get me up to speed using the multimeter and learning how to find faults in circuit boards on effects.
For now, the Brownie is working. Maybe it really was just shoddy transistors, or inappropriate transistors for the circuit, period...NTE457 and J113's are transistors that are "allegedly" substitutes, but I have never heard of anyone using them in a Brownie. Sticking to more standard transistors that have been proven to work in the circuit might have just been the ticket.
Oh my god.
Okay...sounded perfect, but it's not working again. After a while of playing, it starts making a crackling noise that keeps going whether the volume is on or off. Then the pedal starts cutting in and out intermittently. Then it just stops working. Blatty, terrible sounding, with almost zero volume and almost no gain to speak of.
It works great...then stops working. This has been the pattern several times now. Just when I think it's fixed, and working perfect....it cuts out.
Any ideas what measurements I should try now? I'm not sure what it could be, but again, if it's relevant...sounds great, works great, then just stops after about 15 minutes or so of being on, and dies.
Just plugged it back in, and it sounds great...then after several minutes, it dies out again. Definitely a pattern here, but I have no idea what could be causing this. It seems if I leave it off for a while, and then try it again, it works, but under continuous use it just craps out.
Frustrating.
Power it down for a while then power back on. Confirm that it is working and quickly measure the voltages on the transistors.
Wait for it to fail then re-measure the transistor voltages again. Post them here so we can have a look.
The other thing to try is to run the pedal at 9 volts and see if it fails at that voltage.
Made a video demoing what it sounds like when it starts going out. I did find that I could cause this kind of failure by putting the gain knob all the way up and playing for a little bit. It maintained this issue even after bringing the Gain knob down.
https://www.youtube.com/watch?v=W4d5Qkjlrhk&feature=youtu.be
@ Slowpoke
I will try this. For right now, what about polarity? I just noticed that my Fulltone OCD has a Positive Polarity symbol next to the 9-18v adapter, and the Brownie has a Negative Polarity symbol next to the 9-18v adapter. I've never done anything with my Voodoo Lab Pedal Power 2 Plus to accommodate anything, just used the power adapter cords that came with it.
Is this something I should be concerned about?
EDIT: Nevermind...I didn't realize the small "half circle" in the polarity symbol was facing towards positive in both pedals, with the "open" side of the circle facing toward negative, meaning that they're the same. I guess one of them just wrote it upside down, depending on how you look at it.
QuoteI didn't realize the small "half circle" in the polarity symbol was facing towards positive in both pedals, with the "open" side of the circle facing toward negative, meaning that they're the same. I guess one of them just wrote it upside down, depending on how you look at it.
From that description it seems that the polarity would be correct. Make sure that you have the manual for the power supply as some units are rather complex as to the options they can provide.
Your BSIAB2 pedal has a polarity protection diode (in series with positive line) in it so the pedal would not work at all if you had the power reversed.
After listening to your video I noticed that as the played note or chord decays you hear a distinct fizzle then it seems to gate off. This is a sign of poor biasing in these FET based distortion pedals. Something is obviously upset and letting the team down. A crook FET can do this but get the voltages first and we will see.
With the effect powered on at 18v, and sounding like it did in that YouTube clip, these are the readings I got. For simplification, the numbers will all be ordered Gate first, Source second, and Drain last. I did wait for a while and powered it up but it failed to work properly...so for now I'll put these voltages down, hopefully I can get the others down soon.
Q1:
0
6
9.6
Q2:
6
9.6
18
Q3:
0
0.7
9.2
Q4:
5.8
9.1
18
Q5:
1.7
3.0
3.3
Here's the crackling sound, too. It was doing this almost the entire time I was testing it.
(Not *while* I was testing it, specifically...it was doing this noise whether I was probing it with the MM or not)
https://youtu.be/AhxciU-VrCM
I still recommend trying the pedal with 9 volts, just to see if it calms down.
The voltages seem to be close to what I would expect to see at 18 volts. All but for Q5.
Try a different FET just to see if it improves.
Tried running the pedal at 9v, but no change.
Also changed the transistor in Q5, also no change. I can record those voltages if you think it would help. But I haven't been able to get the pedal sounding good for any length of time since it fizzled out the other day. Just continues to do the fizzling thing and hasn't gone away since.
Is the poor biasing simply a result of bad FET transistors? If so, how common is this? Is it necessary to spend a lot of money on a ton of transistors and audition dozens upon dozens of different ones before finding a set that works?
Is how it sounds also consistent with a cold solder joint? Upon the advice here I did look the joints over, and they look fine. I re-flowed them just in case, but that didn't seem to work either. To check again, I *very* lightly moved each transistor, just to see if the legs could flex a little bit, without breaking free from the solder joint...which should indicate a bad joint. They all were able to flex a bit without the legs breaking free.
I would be more than happy to realize I'm at fault here. But I just don't understand why it isn't working! Very confusing.
Either way, I'm so frustrated with this I decided to buy one of the BSIAB II kits. I'm not *completely* giving up on the Brownie yet but it is looking pretty bleak. I just can't wrap my head around what the issue is.
https://www.amazon.com/Socket-Transistor-pitch-inch-2-54/dp/B075Z1GH1K/ref=sr_1_1?ie=UTF8&qid=1520142336&sr=8-1&keywords=transistor+sockets
I got those sockets originally for the Brownie. I've been planning on using these for all the transistors when I build my BSIAB II from the kit.
Any thoughts on that? I've heard some people say that sockets are not as reliable as soldering directly to the board. However, for all the issues I'm having, being able to swap them out quickly seems like an advantage. It would also guarantee that I wouldn't accidentally damage them by overheating them.
I hesitated a bit, as the CMATMODS Brownie is made by a reputable builder, and I highly, highly doubt there is anything wrong with anything else on the board...like in the first comment in this thread, it was working before I tinkered....then I tinkered and it stopped working.
The only thing I can imagine is that I somehow made bad solder joints, or I have bad FETs. I am more inclined to think that they're just bad joints. I used flux when I soldered them all on and it seemed to flow well and touch everywhere it should and nowhere it shouldn't. But if they are bad, I wonder if there's any way to tell? I visually inspected them to the best of my ability, and while they're not gonna win any beauty contests they seem pretty solid.
Let's see. Your pedal was working and then you decided to try different transistors in it to make it sound 'better' when running at 18 volts. Not a silly idea at all.
Here are the variables; There is no guarantee that your new transistors are able to work in the circuit or work at all.
De-soldering can damage the circuit board (mainly the through plating in the component hole pads).
Soldering can also introduce problems - Shorts, dry joints, overheated components....
So really there is very little that can be wrong. The most likely problem would be unsuitable (or unusable) transistors or a solder connection point is faulty. The fact that the pedal sort of works and then fails points the finger of suspicion towards the transistors. Installing those transistor sockets may be a good idea. Some are really good and hold the transistor leads very well and some are terrible, bordering on useless. I generally solder the transistors into the socket (if I bothered to use one) when I've got everything working properly.
I think that Smallbear has suitable transistors available that are known to work correctly. This would save you from buying a fortune's worth of transistors and auditioning them - which is best done in a working pedal. Your new kit will also have the correct transistors (assuming that you bought the full kit and not just the board).
Good idea to get the kit. Always fun to build things. But get it going on 9 volts first and then try 18 volts. Beware of the voltage ratings of any electrolytic or tantalum capacitor that may be used. Make sure that 18 volts will not exceed it.
can I request a few numbers? with the power off, and the meter to Ohms, can you give us the resistance reading from the gate of Q5 to ground, and from the gate of Q5 to the supply line? and just for fun, the resistance from the gate of Q3 to ground, with the gain pot at each extreme of rotation.
How do I do this exactly?
I went through all the Ohm settings on my multimeter, which one would be appropriate for this?
I didn't get any readings at all unless I had the red probe on ground, and the black on the Gate of the transistor.
In which case I got:
Q5 Gate to Ground: -598
I get ~631 if I put the black probe on the Gate of Q5 and the red probe on the positive lug of the 9v adapter. Is this what is meant by the supply line? It started around 644 but with continual testing the number gets lower and lower, like a minute later now it's reading at 621.
Doing my best to test what I can but I'm pretty sure I'm doing this wrong. Any clarification? Is black probe on Gate of Q5 wrong or is that what I'm supposed to do?
I've been using the tab on the input jack that connects to the negative terminal on the 9v power supply as Ground. Is that incorrect?
Going that way, I found -589 with the Gain all the way up, and -601 with the Gain all the way down on Q3.
> bad solder joints....any way to tell? I visually inspected them to the best of my ability, and while they're not gonna win any beauty contests they seem pretty solid.
Get good light. Get magnifier. If you are over 40, use your readers too.
Joints should at least pass the Beauty Contest Swimsuit Test. You should be able to see the parts through the suit/solder. With blobbed solder you can be SURE the solder has "wet" the joint.
A bad FET is *possible*. I recently saw a case where a transistor was dropping in and out of conduction (from a tech who knows bad solder all too well). But it is far less likely than bad joints.
Just re-flowed all the joints, especially on Q5.
Plugged it in, ran it, and worked great for about 3 minutes. I checked the Drain leg on Q5 while it was working great and it was reading out right at 4.5v after adjusting the trimpot.
When it started to cut out, I quickly put the meter back on. It Read around 1v. Then it jumped all around from 2 to 3 and back to 1 and then finally settled somewhere around 2.5v to 3v. Very quiet, very low gain, very fizzly sounding.
Re-flowed it again....started out at 4.3v.
1 minute later, as I'm sitting here writing this, I hear the static hum/buzz of the pedal being on disappear. I go over and check the Drain leg of Q5 again and it's at 3.0v. Starts crackling, check it again, it's at 3.37v.
This is all without doing anything at all other than just leaving the pedal powered on and plugged in. Not moving it, pressing the switch or changing any knobs or anything except intermittently checking it with the voltmeter.
I ordered a good Solder Sucker that should be coming in soon. I noticed that the more I tried to re-flow, the more solder built up because I forgot I'd tinned the iron beforehand.
Have a quick look at this picture.
(https://s18.postimg.org/kreczqatx/BSIAB2_Q3_Sod.jpg) (https://postimg.org/image/kreczqatx/)
Q3 Source leg seems to be missing solder on the top layer pad. I cannot see if there is a track connecting this pad to anything else (on the top layer) but there may be. If I recall you did say that you had trouble with damaging the plate through on Q3's connection pads. You may need to see if you can get some solder into the connection point.
Another thing to see if it makes any difference is to re-install the 0.0022uF capacitors and see if the pedal returns to the original condition.
what make and model is the meter you are using, please?
looking at the BIASB II from ggg circuit dia - the "supply line" is the positive rail, the V+, the line connecting the tops of R4, R11, R16 and C11. between there and ground, you should have vrr near 18V w/ the big supply, and 9V w/ the smaller supply.
on that circuit, Q5 gate connects to ground thru R14, 82k. with black on ground and red on gate, you should show 82k (or whatever your variant circuit has there). similar, Q3 connects gate to ground thru R19, 500k pot. at one extreme, that should read near 500k, at the other 0R. as neither gate shows a connection to "supply", there should be no sort of sensible resistance reading between gate and supply, it might show a counting or an overload.
[if either/any of the jfet gates doesn't have a DC path to ground, ie a resistor, the gate will wander as it likes, usually following leakage thru the cap, if there is any. sometimes the cap starts out leaking enough to 'sound right', then tails off into mis/bad bias and splut/spit.]
I'm using a Cen-Tech multimeter from Harbor Freight. Got it for free. Not sure of the quality but I can't imagine it would be great.
My caps from Stewmac came in today. Whatever they are, they look identical to the caps that were on the Brownie. I replaced that .0022uF cap with a .001uF, but it was green, looked skinnier and taller, and well...I put a .001uF cap in from Stewmac that looks identical to the other caps. Not sure if that should make any difference. Both caps I used were rated for 100v.
My Engineer Solder Sucker came in today. And I am blown away at how good it is. I ended up taking the pots out, and using the soldering iron pushed against the terminals on the back of the board, put the sucker down on the top of the board and pushed, and then sucked the solder out.
I got all the holes for the transistors completely cleaned out. No remnants of solder or clipped transistor legs. Then I soldered the sockets in. That proved to be a little challenging. If I turned the board over the solder them, they'd just fall out. So I just held the socket down with one finger on top of the board, then quickly used some solder from tinning my iron to touch the terminal on the back of the board, and hold that one leg down.
Then I'd solder the other two legs in the right way, and eventually the last leg:
Heating up the through-hole first, until it's hot enough for the solder to flow onto it. I think I might have had some bad joints earlier as a result of not doing this consistently or very well. Inadvertently I might've had a couple joints where I merely transferred solder from the tip of the iron to the joint, rather than getting the joint hot enough to have solder flow throughout it.
I am not convinced that I'm out of the woods yet. Have had way too many close calls with this thing.
But for at least 5 minutes of plugging it in after cleaning out all the holes and soldering the sockets in, it seems to be working well. All the transistors except for one of the original MPF102's are in sockets now. I used a pair of round nose pliers to bend the legs to fit. Is that proper procedure?
The Drain leg of Q5 is reading out at 4.5v, right where I left the bias with the trim pot. Again....at least for the first couple minutes of playing. I'm almost scared to keep going! So many times now it seemed great and then just stopped working. Seems to be the pattern.
@ duck
Man. I am gonna have a time with the BSIAB II. I'm struggling pretty mightily to follow what you're talking about, and I have the schematic for the BSIAB II opened on my other computer monitor as I'm typing this! Looks like hieroglyphics to me, although I watched a few videos last night on how to read schematics. Gonna take a bit for it to click, I'm sure. Big help that you mentioned Q5 Gate goes to ground through R14...that's helped me with understanding a bit of how to read schematics. I'm a *rank* beginner but I'm doing my best to learn.
For now I'm gonna demo the pedal and see if it holds up. I just plugged into my 18v power supply and it's working okay with the sockets in. I did the best job I could to get the sockets in, although a couple went in crooked. That was before I came up with that makeshift method for soldering them in straight. I would love to know if there's an "official" way to solder them in straight and clean. i.e., making sure they don't move or fall out when you flip the board over the solder from the other side.
I would love to take some measurements soon. I will say, however, that my Brownie does seem to be different from the BSIAB II, somehow. I counted the number of capacitors and resistors on the BSIAB II, and the Brownie I have has more capacitors and more resistors, something like several more of each. I am not sure how identical the boards are for the two of them, although I would assume they are pretty close. I've heard that the Brownie is a licensed, direct clone of the BSIAB II that uses the GGG board, so I found it odd that my Brownie has more caps and resistors than are listed in the schematic/bill of materials for the GGG BSIAB II.
(https://s14.postimg.org/qbiw0r1f1/28158580_173162323407065_2125928414027186176_n.jpg) (https://postimg.org/image/qbiw0r1f1/)
Thanks again guys for all the help. I really appreciate it. And that description of why it could be doing what it's doing (any of the JFET gates not having a DC path to ground -- i.e. a resistor) was very helpful. It's a lot to take in being a newbie but I feel just this little project alone, and all the advice here, has taught me a lot.
I am not confident that this pedal will continue working. Given what's happened before. A bit paranoid now.
But it's working much better than last night after sucking all the old solder out and resoldering new sockets in. I'm very happy with the solder sucker and I figured the best way to go over the joints would be to redo them from scratch....get all that old solder out and put some fresh solder in, and pay very close attention to how I'm doing it.
Cut out again. Same as always...works great and then stopped. Took maybe 20 minutes of playing this time.
@ duck
"can I request a few numbers? with the power off, and the meter to Ohms, can you give us the resistance reading from the gate of Q5 to ground, and from the gate of Q5 to the supply line? and just for fun, the resistance from the gate of Q3 to ground, with the gain pot at each extreme of rotation."
Q5 Gate to ground = 82k.
From what I could tell, the supply line is basically the 9v adapter jack that I'm plugging the power cord into. I can't tell which is + or -, but holding the black probe on Ground, and using the red probe to test the tabs on the 9v adapter...one of them does read out at 18.55v with the 18v power supply plugged in.
Q3 Gate to ground reads 511k with the Gain knob all the way up. It reads 0 with the Gain knob all the way down.
Slight - that is good on a few counts. the resistance figures clear the gate bias to some degree, they are what would be expected. and, it seems you are coming to grips with using your meter!
your one-pin soldering of the sockets is the approved method. one leg works for most solderings of that sort, as long as you rework your first tack-joint so it is up to par before moving on.
but we still no closer to the fault/fix.
Kit came in today. Got it done. Took quite a while.
It doesn't work -__- Most immediate thing I realize wrong is that Q3 Gate has no reading at all. 0v. And if I touch it with the probe while the pedal is on, it goes to a buzzing noise. Not sure what that means.
I thought the socket might be bad. After 15 minutes of using the solder sucker to no avail to get the socket out, I had to clip it. It was extremely difficult to get at it with the board wired up and installed, and I didn't leave an incredible length of wire to flip it over. It ended up ripping the entire top of through-hole out of the PCB on one leg. F***!
Again...checked all the transistors against the reference voltages. Everything was in spec expect Q3...on the Gate of Q3 to ground, with the amp and pedal on, I was getting 0v and also a buzzing sound.
Issue I'm having is almost zero volume, and no gain.
I resoldered the transistor in. Funnily enough, the socket was probably fine. Where the through-hole was completely ripped out, I am still getting around 4.7v (Drain leg of Q3).
But still 0v and buzzing on Gate of Q3. Although the reference voltage is 0.3v on Q3 Gate, so....doesn't seem too crazy. The buzzing was concerning. I have not audio probed the circuit yet.
I am just about ready to quit here...or I would be if I didn't know that problems with first time builds are really common. Just hard not to be frustrated when I'm over 190 bucks in the hole and just have two non-functioning pedals, and for the life of me I cannot figure out what's wrong with either of them.
But after I found the pedal didn't work, I was like OK...let's test it....but when I accidentally tore the through-hole off the PCB for a few seconds I felt about ready to throw a brick through the window. Or my BSIAB II, which is about as functional as a brick at the moment.
I spent all day today working on building the BSIAB II from the kit, and paid meticulous attention to the wiring everywhere. I soldered everything in absolutely as well as I could, even using my new tip cleaner for my soldering iron inbetween every joint. I was really excited when I plugged it in and saw the light go on, then....nothing.
The LED works, and the pedal has sound, it's just that with the volume and gain all the way up, it's about 10% as loud as my clean volume, with absolutely no gain to speak of.
And I did notice that the electrolytic cap in the BSIAB II that I got was rated for 16v. Not sure what that means, but I was careful to only run the pedal at 9v, and did not plug it into an 18v power supply for even a nanosecond. I thought I remembered reading something like that, and not to run at a power supply that's rated higher than an electrolytic cap in the circuit. I could be wrong but I wasn't gonna take any chances with that.
Ugh...
https://www.youtube.com/watch?v=KuVGcm7EfKU
(https://s14.postimg.org/yvicskvql/20180308_025639.jpg) (https://postimg.org/image/yvicskvql/)
(https://s14.postimg.org/pnq4bwyz1/20180308_004909.jpg) (https://postimg.org/image/pnq4bwyz1/)
I left out a .0022uF cap to give it more high end, and replaced another cap with a .001uF, the other .0022uF. I can't imagine how this could possibly cause these issues. But that's all I did that was unorthodox.
The parts that came with the pedal were a bit wonky looking, particularly the blue rectangle capacitors. I did some research online and to my knowledge these were the correct locations for those parts.
For the record, I did have 4 spare parts after I was done. The .0022 caps, which I expected, as I didn't use either...
And two other caps that I don't know the value of. I think they're .1uF, as I didn't see any traditional looking .1uF caps in the kit, and thought they were missing from the kit. I didn't realize that the blue rectangles other than the ones I had on the board were probably .1uF caps. I had some spare .1uF caps from when I was making the audio probe, so I used those. So I think all the parts that were left were ones I left out and replaced with my own of the same value, except that .001uF. Here they are, just in case:
(https://s14.postimg.org/3r3lbalpp/20180308_044602.jpg) (https://postimg.org/image/3r3lbalpp/)
(https://s14.postimg.org/hkry0dgvx/20180308_044608_HDR.jpg) (https://postimg.org/image/hkry0dgvx/)
(https://s14.postimg.org/6l6qory6l/20180308_044620.jpg) (https://postimg.org/image/6l6qory6l/)
Here are some measurements I just took of the BSIAB II I built today (not the Brownie). Power supply/9v terminal on PCB is reading out at 9.3v when hooked up to 9v power supply, with black probe on Ground.
Reversed the jacks...nope. They're in correctly.
There is a very midrangey sound to it..the gain is non-existent but from what little I can hear of the tone through the pedal, it sounds like it has a blanket over it. The tone is completely clean and very very quiet with the volume all the way up, and sounds like someone rolled the tone knob all the way off. Adjusting the tone knob on the pedal does not affect this, although it does change the static hum of the pedal as expected...I can hear the frequency going up so the tone sounds like it's working.
As for the transistors: All readings will be ordered Gate, Source, Drain:
Q1: 1.8v, 1.8v, 3.8v
Q2: 3.8v, 3.13v, 8.55v
Q3: 0.01v, 0.26v, 4.81v
Q4: 2.85v, 4.81v, 8.55v
Q5: 0v, 1.04v, 4.66v
Q5 Gate to Ground: 82.5k resistance
Q3 Gate to Ground: 535k resistance with Gain pot all the way up. Seems like normal readings throughout, with it tapering down in resistance as I lower the Gain knob until it gets to 0 at the bottom.
I still don't get how to read schematics, but it appears that Q2 Gate and Q1 Gate both go to ground through 1M resistors...my current multimeter doesn't have that setting. It goes between 200 and 2000k resistance and that's it. I tried testing resistance on Gate to Ground from Q1 and Q2 and got nothing, presumably because I can't set my meter to test them properly. Also assuming that I'm correct that they go through 1M resistors each to get to ground, which I could be wrong about.
These are all the measurements I have for now...but yeah. Almost zero volume, ZERO gain even with the gain knob all the way up.
Do not get discouraged. You have probably made a minor mistake when building the kit. Should not be too difficult to sort it out.
Check for a short between Q1's Gate and Source. They should not read the same.
If it is shorted once you clear it Q1 and Q2's voltages should make more sense.
Your multimeter can read 1M resistors quite easily. The 2000K range is 2M, so the meter's maximum resistance that it can read is 2M.
The 16V on the electrolytic means 16 volts - maximum. Go over 16 volts and it will get damaged.
The blue box type capacitors are 0.1 uF - The marking u1 means 0.1uF. The 63V means 63 volts maximum.
here, I'll type some random and confusing things about the circuit and stuff.
capacitor and resistor markings - to AVOID any possible errors with values, it was decided to replace the decimal point with the multiplier. so, instead of 2200 ohms, you'd put 2k2. with 0.1uF, you'd put 0u1, which is ugly, or use the multiplier that didn't need the decimal, ie 100nF. [many people don't like using the nano prefix, for some reason.]
0.000,001F = 0.1uF = 100nF = 100,000pF
you can also use the numeric code as on box-caps, 104 [which is 100,000 pF]. a 2k2 resistor would be 222. the "K" on your blue cap is the tolerance code. 63 is the voltage limit.
your circuit - Q1, Q3, and Q5 all have their gates referenced to ground, you just follow those resistors. Q1 should read a little over 1M. because they are ground referenced, the gates should read 0V DC. @ Slowpoke - check me here, please.
but, the gates of Q2 and Q4 are held mid-way between "supply volts" and ground because of the equal value resistors connected to them. your meter will read less than half V+, however, because it will load-down the lower resistor [making it look instead like a ~500k] when you measure.
and, to test. now you have sockets fitted, you can break the circuit into two parts, the front end and the arse end. IF you pull Q3 out of circuit, you can inject your test tones into the C1//R1//R2 junction, and then listen to the result at the C4//C5//R6 junction, and then thru the gain pot, and test at the empty gate-pin of Q3. if you get signal, and some gain, you can say front end is ok.
power off, refit Q3, and pull out Q1 and Q5 (for fun). now inject your test tone into the C4//C5//R6 junction, and monitor the result at the empty Q5 gate pin. work the drive pot, and you should have some gain control over a somewhat gained signal. if so, you have cleared most of the arse end, now power off, refit Q5, and then monitor your signal at the junction of C8//C9//R7. you should have signal, possibly less than before. now move through the tone section to the right, testing all the lugs of the tone pot, and the junctions following up to the output.
so now you've either found something, or cleared everything. record your voltages at each step [don't measure DC volts with a signal applied] and see what changes where. good luck, come back with some questions and or results.
I've gotta go to bed, but a couple parting thoughts before:
I audio probed the board. Perhaps it's significant that I was getting no audio from V1, which is the wire connecting the circuit board to the input of the Volume pot. I think it's the input, anyway. It's the rightmost tab on the Volume pot.
Q5 was, I think, the only transistor getting audio signal.
How should I test for a short in a transistor? What could cause a short?
What's the reason to not test voltage when the power is on? But it's okay to do that when adjusting the trimpot, right?
I hope I didn't damage anything by doing that. Probed around the electrolytic cap a few times as well. But I've been checking voltage on various parts with the power on. If that's not good then I'll stop doing it.
If I could eventually fix the Brownie AND the kit pedal, that would be great. That's what keeps me going. I know next to nothing right now so all this is to be expected. I'm gonna get some sleep.
I've been trying very hard to follow the schematic. I don't fully understand it yet but I can see how schematics go hand in hand with the audio probe. You have to know where you are in the circuit to identify where a fault is, and what that fault does to the components that follow it.
V1 getting no signal and that being the connection between the circuit board and the volume pot seems pretty significant, though I have no idea what it means. Thanks for the replies as always, will check up with all this ASAP.
Quote from: Slight Return on March 08, 2018, 11:25:35 AM
What's the reason to not test voltage when the power is on?
Who said that? As I hinted in my post on page #1, if you don't supply any volts (i.e. you don't power it up), then you can't expect to measure any volts anywhere in your circuit. You don't get anything for nothing in this life, and that includes volts! :icon_biggrin:
If you're testing for voltages, it needs to be powered up. If you're audio-probing, it needs to be powered up. If you're testing resistance or continuity (same thing), then
no power.
OK. A few things to clear up.
When doing resistance (or continuity) tests on a circuit the circuit must not be powered. If it is powered you would get some really weird measurements on your multimeter, none of which would make any sense.
When doing voltage measurements the circuit must be powered otherwise there would be no voltages available to actually measure. However you must be careful as not to slip with your multimeter's probes and cause a short circuit.
A short circuit can occur when something conductive (meter probe, sliver of solder (solder bridge), wire and so on) accidentally connects one part of a circuit to another part of the circuit. This accidental connection will stop the circuit from working in the manner that was intended.
Finding a short circuit can be difficult but quite often they are obvious (visual inspection). Using a multimeter set to continuity test (if it has it) or the low ohms resistance setting (200 on yours) is usually the best way to find a short if visual inspection is unsuccessful.
The V1 connection point actually is a ground point. There will be no audio on this connection (unless something is seriuosly wrong somewhere). The input audio connects to the I connection point. The output audio from the effect is the V3 connection point. This connection goes to the volume pot. If the effect is working there should be a very high level of audio at V3 (very loud).
Here are some voltages from my BSIAB2 (which is working). The voltage measurements where taken using a cheap multimeter and you will note that some are different from the GGG build document. This is normal and is due to my selection of transistors and using a cheap multimeter. With no input signal applied, battery at 8.97 volts and with Drive, Tone and Volume centred (mid-range) I get the following;
Gate Source Drain
Q1: 0V 0.58V 5.08V
Q2: 2.98V 5.08V 8.94V
Q3: 0.01V 0.04V 4.56V
Q4: 2.98V 4.56V 8.94V
Q5: 0V 1.01V 2.64V
Now, as Duck pointed out the Gate's of Q1, Q3 and Q5 are tied to ground through some resistors. 0 volts or very close to 0 volts is expected at those Gates. The Gates of Q2 and Q4 are each connected to voltage dividers made up of two 1M resistors and you would expect to find the voltage on their Gates to be at half the supply voltage (4.5 volts) but the input resistance of the cheap multimeter loads down the voltage divider and gives us a false reading of a lower than expected voltage. This is nothing to be worried about but it is something to be aware of.
Notice that Q5 has a lower Drain voltage than what you currently have. This is again due to transistor selection and where I found the setting for the trimpot to sound "the best".
Your Q1 transistor is really odd with its voltage readings. As I said before, there is most likely a short circuit between its Gate and Source. If there is a short the effect cannot work. Let us know how you go.
***Edit: Ah, I see that bluebunny has covered the powered / not powered subject. Quite well in fact. Much clearer than my ramblings. :icon_biggrin:
@ Slowpoke
"Check for a short between Q1's Gate and Source. They should not read the same.
If it is shorted once you clear it Q1 and Q2's voltages should make more sense."
Do I check for a short by setting the resistance on the MM to 200ohms and then probing with the power off?
Either way, I just tried testing the resistance. If I didn't get a reading, I reset the MM to change how many digits there were until I did. Here's what I got:
BSIAB II Build:
Q1: Ground to Source: 38.2k, Source to Ground: 42.1k
Q2: Ground to Source: 42.7k, Source to Ground: 38.9k
Q3: Ground to Source: Starts at 230k, and kept increasing. I stopped after 10 seconds or so when it hit 260k. Source to Ground: Same thing.
Q4: 492k both ways.
Q5: 85k both ways.
CMATMODS Brownie:
Q1: 982k both ways.
Q2: 491k both ways.
Q3: 111k both ways.
Q4: 488k both ways.
Q5: 86k both ways.
Brownie Q1 to Ground: 982k
BSIAB II Q1 to Ground: 1k
It would appear that, somehow, on my BSIAB II build, Q1 is either not going to ground or bypassing the 1M resistor somehow? Or is it shorted out? I'm confused but I know that that isn't right.
I still want to get the Brownie running too. Not sure if those numbers help any with diagnosing what might be wrong. That pedal has a different issue, as it was working great for a while, and then just started spluttering and splatting and lost almost all volume and gain seemingly at random after playing for a while...whereas the BSIAB II simply does not work at all.
Sorry if I'm not providing all tests possible or responding to every post possible at the moment. I've read and re-read everything and am doing my best to keep up.
Next on my list will definitely be doing the audio probe test for the two ends of the pedal, as suggested by duck.
You are getting some interesting results.
Is there any chance that you can post a picture of the solder side of the GGG BSIAB2 board please.
Here she is:
(https://s14.postimg.org/wfv8meagd/20180308_230201.jpg) (https://postimg.org/image/wfv8meagd/)
This post is concerning the GGG kit only.
Refer to the following picture;
(https://s18.postimg.org/umhycjqvp/GGGBSIAB2_PCB2.jpg) (https://postimg.org/image/umhycjqvp/)
Make sure that the pedal is in Bypass mode and is passing the guitar's audio to your amplifier correctly. If it does then move to the next step.
Disconnect power to the pedal, remove the input lead (from guitar) and the output lead (to amp), while leaving the pedal in Bypass mode.
Set your multimeter to resistance test 2000K range. Place the black test probe onto point 2 (refer to picture) and the red test lead onto point 1. You should read around 1M.
Now set your multimeter to the 200 range. Place the red probe onto point 5 (Q1 Drain) and the black probe onto point 3 (Q1 Gate). Your meter should display 1.
Move the black probe to point 4 (Q1 Source). Your meter should display 1 again.
If all this tests as described - no shorts are on Q1. Good.
Plug the guitar's input lead back in. Set the guitar's volume to maximum. Do not apply power to the pedal. No need to plug your amp in at this stage.
***Edit: Forgot this bit. Click the stomp switch once to set Engaged mode.
Set your multimeter back to the 2000K range and place the black test probe back onto point 2 (refer to picture) and the red test lead back onto point 1. Depending on your guitar's pick-up coils you should read above 2K (on the 2000K range 2K would be displayed as 002). If the measurement is lower than that check that the pedal's input socket is not shorting against the Drive pot's metal body.
Let us know what you find.
[clarify] sorry, when I said power off, I meant that if you are going to pull fets from sockets, or ram them into sockets, you should off the power, just in case. but then, once your parts are safely seated or removed, you power up, and go about your voltage measures. carry on. [/clarify]
@ Slowpoke
Point 2 to Point 1: I get nothing. Meter reads 000.
Point 5 (Q1 Drain) to Point 3 (Q1 Gate): Meter stays at 1.
Point 4 (Q1 Source) to Point 3 (Q1 Gate): 38.7k.
I didn't continue with the testing yet, as apparently this means there is a short on Q1. What could cause this, and what can I do about it?
***EDIT: Having just noticed that the stomp switch shorts the board's input to ground in bypass mode (sorry). Set the pedal to Engaged mode (with no power applied) and continue as described below.
When measuring points 1 and 2 your meter should be set to the 2000K range on the resistance test. If everything is OK you the meter should show 1000 or close to this. However you measured 000 which is a low resistance, possibly a short. Set your multimeter to the 200 range on the resistance test and remeasure points 1 and 2. If there is a short circuit the display would show something lower than 10.
Anyway, solder the input wire going to connection point I on the board. Remeasure points 1 and 2 with the meter set to the 2000K range. If everything is good the meter will show somewhere near 1000 which is 1M. If it does, good. If it still shows 000 then there is a low resistance or a short circuit somewhere with R1, C1 and R2. Look very closely and you should be able to find it. A fine sliver of solder can cause this and it can be hidden in the flux residue on the board.
Now, if the meter showed 1000 on the last test there may be a short with the input lead that was connected to the I board connection point. Look very closely at the terminals on the stomp switch as there may be a fine wire touch between terminals.
Don't worry about the 38.7K reading on Q1 yet. Sort out the problem with the input area first.
For points 1 and 2 in the pic:
With it engaged and the power off, and my meter on 2000K, I am getting 001.
If I put the meter on 200, then it reads 01.2.
Looked for about 15 minutes at the board on both sides at R1, C1, and R2, and re-fluxed, and re-flowed all those joints. I got a little glue brush with some isopropyl alcohol and cleaned all the flux off of the board, top and bottom, afterwards. While it was wet from the alcohol I could see pretty clearly, and I could not see anything bridging any of the solder joints. I carefully went in with a little toothpick and got a little blackened flux/solder out of the way in some spots but it didn't reveal anything.
Measured again, and....no difference. I couldn't see any pieces of solder bridging any connections. One of the caps they gave me was wonky (two legs very far apart, when the pads designated for it were very close together), but neither of the legs were contacting anything they shouldn't be.
I also looked over the stomp switch and could not see anything bridging anything between any of the terminals. Does the orientation of the switch matter at all? I just soldered it on following the wire diagram but I didn't know if it needed to be oriented a certain way or not. It just looked like a square with no indication of what way is "right side up," if there is one. Not sure if that matters.
Very interesting result.
De-solder the input wire (green) at board connection point I ( I - not test point 1). Set your meter to 2000K and measure again across test points 1 and 2. You should read around 1000. If it still reads 000 de-solder C1 (250pF capacitor - probably marked 251) and measure again. If it now reads 1000, C1 is probably faulty.
Set your meter to 200 and test across C1 whilst it is de-soldered from the board. If it shows near 000 it is faulty and should be replaced.
I am surprised that you are having trouble with the BSIAB2 kit as you have done a very good job building the circuit board.
Let us know what you find.
Still reading 001 after green wired removed from circuit board.
Still reading 001 after C1 cap removed. I tested C1 with meter at 200 and got 1...the meter simply doesn't change.
Interesting indeed. Possible another component is faulty as well? Also, for future builds, is it good practice to set the meter to 200 and test each component before soldering it in? Are there components that this method wouldn't work for?
Meanwhile, I've sent my Brownie to Chad at CMATMODS for repair. I did ask him if possible if he could tell me what's wrong with the circuit after fixing/replacing it. I'll have enough on my plate with the BSIAB II and if I have a functioning version of it it'll probably be easier not to get burned out on it. In a sense I'm actually quite enjoying the learning process here and I feel I'm having more fun learning these things than I would be having using the pedal.
Or at least, the same amount of fun.
Ironic, I know :)
Odd result. OK on sending the other pedal off for repair. Sometimes it is necessary.
C1 is most likely OK. Testing parts prior to assembly is a good idea but usually parts are fairly reliable. But testing resistors to make sure that you have the correct value is a very good thing to do. Sometimes the colour (color) bands are difficult to see and some can be marked wrong.
Now, where C1 was soldered to the board, set your meter to the 200 range and measure across the two solder pads.
Your meter should show 1.
Just measured. Across the two pads where C1 was, I am getting 1. I still need to work on neat component removal. I had to use pliers to pull the legs out after sucking as much solder out as I could. I do remember it going in quite tight. I tried to be careful as pulling on parts like that seems it could pull the pads out with it.
I assumed it would come out easily if I removed all the solder. Perhaps I wasn't as thorough as I thought. I could see plenty of light shining through the pads. Just want to make sure my technique is good so I don't damage the PCB by removing other components.
Removing soldered components can be difficult. It is no always possible to remove all the solder prior to removal of the component. With components with two leads (more leads make this more difficult), heat one solder joint while applying a SMALL amount of lifting force onto the leg being heated, melting the solder and pulling the lead free from the board. Clean up the solder still in the hole with your solder sucker. See if you can find Solder Wick ( De-solder Wick, Solder Wik ). It's a flux coated braided copper flat wire which when placed onto a solder joint and a soldering iron is applied to the braid, heating both the braid and the joint, the solder flows (wicks) into the braid and away from the joint. Careful control of both heat and time are needed to avoid board damage due to excessive heat but the Wick is very effective.
Re-install C1 and redo the last resistance test. The meter should read 1. If it does, resolder the green input wire back to board connection point I
With the pedal in Engaged mode (not Bypassed), with no leads connected to the pedal's input and output sockets, your meter still set to 200, measure across C1 again. The meter should display 1.
If it does display 1. Apply power to the pedal, set your meter to the 20 DC range and measure the voltages on Q1.
Let us know what you find.
Will get this done ASAP. Broke the leg of the cap trying to put it back in; must've fatigued it with the pliers during removal.
How can you tell if the board is damaged from excessive heat? There was one or two times on the board I think I was holding the iron lazily and it wasn't heating the pad so well, and I could've had the iron on one spot for as long as 10 seconds without the solder melting.
I'll need to buy another cap to replace that one. 250pF ceramic cap...I'll remember that. Might as well got some solder wick while I'm at it.
That is disappointing. The small ceramic disc capacitors can be a bit fragile and it is easy to break the legs off them. If you have to bend their legs, you try not to bend the legs right at the body of the capacitor. Leave distance of about 2mm (3/32") from the body before bending. That way you don't stress the leg bonding to the capacitor. Not to worry.
When you get some de-solder wick, find a junked electronic item (old stereo, radio, whatever you find) and practice de-soldering. It will not take too long to get the hang of it. I forgot to mention that as you use the wick it will become loaded with the solder that it has "wicked" up. You cut of the loaded (used) section and dispose of it sensibly. I generally de-solder a few solder joints then cut off the used section. If you leave the used section attached it will act as a heatsink, slowing the melting of the solder you want to remove.
Damaging a board through overheating. It is easy to do but boards are fairly tough. You will smell it as it starts to happen. The smell is unmistakable. Visually the board will start to discolour and may bubble up (fibreglass boards). Phenolic boards (brown colour) don't smell too bad when overheated but the copper traces and component pads de-laminate off the board.
Holding the iron to a pad for over 10 seconds is excessive. Fortunately your iron had poor heat conduction at the time so no harm should of been done.
Believe it or not you don't actually need the capacitor C1 to be installed for the next test. C1 is mainly used as an RF choke point, that is it helps keep the pedal from picking up radio stations or other sources of RF (radio frequency). You can perform the next step without C1 being installed.
Set you meter to the 200 range resistance test. Measure across the two solder pads where C1 would be installed. If the meter displays 1, then go to the next step.
Resolder the green input wire back to board connection point I. With the pedal in Engaged mode (not Bypassed), with no leads connected to the pedal's input and output sockets, your meter still set to 200, measure across C1's solder pads again. The meter should display 1.
If it does display 1. Apply power to the pedal, set your meter to the 20 DC range and measure the voltages on Q1.
Let us know what you find.
Just did the test. Everything cleared.
On Q1 I get:
Gate: 0.99
Source: 0.99
Drain: 5.28
Looking good.
OK, next test.
Meter set to 200 range resistance check again, no power applied and no output lead connected.
Pedal set to engaged mode and no input lead connected.
Measure across the input connector - yellow wire and black wire. Your meter should show 1 (no short circuits).
If this is right the on to the next step.
Connect an input lead with nothing connected to the other end (not plugged into your guitar) and retest across the input connector. Your meter should show 1. If it shows other than 1 - say 000, the input socket is shorting somewhere, usually to the pot body under it.
Let us know what you find.
So test the lugs of the input jack, right? If that's correct, I did that and got 1. Seemingly it checks out.
It also read 1 while a jack was plugged into the input jack. Same reading: 1.
This is looking very good. Now for the next bit that will make you think that I have lost my mind.
Look at Q1. Notice that the flat face of its body faces towards the centre of the board.
Take Q1 out (unplug it from the socket) and rotate it so that the flat face is now facing the outer edge of the board (plug it back into the socket).
Connect your guitar and amp. Apply power and test your pedal.
If it still isn't working correctly, measure the transistor voltages again and let us know.
Good luck.
With the transistor reversed, it still doesn't work, but with the knobs all the way up I do get at least some signal. About 5% as loud as my clean volume but still something. For a while it was not having any sound at all. However, the lack of drive/distortion was still there. I only mean that there was guitar signal going through and coming out, instead of complete silence, but the original problem remained the same.
After being on for about 2 minutes, though, all the sound went out, and was replaced by a loud static/crackling sound that only goes away when I switch the pedal off.
Now it reads, with Q1 reversed:
Q1:
Gate: 6.14
Source: 0.65
Drain: 0.00
Q2:
Gate: 6.22
Source: 6.22
Drain: 8.55
Q3:
Gate: 1.95-2.21*
Source: .9-1.3*
Drain: 1.2-1.4*
Q4:
Gate: 1.86-2.31*
Source: 1.25-1.41*
Drain: 8.57
Q5:
Gate: 0.06
Source: 1.09
Drain: 3.55
The * numbers simply indicate the meter looked very unstable when testing these. All the other numbers got a solid, static result...when I tested these, the meter seemed to jump very quickly between higher and lower values in the indicated range, and wouldn't settle on a single voltage reading.
OK. The reversal of Q1 answered my concern that you may have had a transistor that had its Drain and Gate transposed. It happens a lot these days.
Put Q1 back into the normal position and try the pedal again.
Does that mean that on a lot of transistors made today the Drain and Gate legs are reversed?
I put Q1 back in the normal position and tried again...nothing but static/crackling that seems to get louder and louder over time. No signal. Measuring Q1 normally oriented:
Gate: 0.84
Source: 0.84
Drain: 5.26
If the pedal worked with Q1 reversed, would that indicate that the Drain and Gate legs were reversed? Do the measurements indicate that they're properly oriented since the Drain read 0.00?
Part of the problem with TO-92 packaged FETs (Field Effect Transistors) is that the most common units that are used in effects pedals are no longer manufactured in large volumes and they are getting hard to obtain. So some units may be low specification devices - they work but may not work as well as you would expect. Some manufacturers did use different pinouts for the same series - because someone ordered them that way or it was a manufacturing error. Most suppliers do try to supply the pedal builder fraternity with good FETs but sometimes bad or not so good units make it through. Ebay can be a nightmare to buy these types of FETs through. I gave up a few years ago.
It can be a bit of a effort to sort through what is currently available. But there are ways to sort the gold from the dross.
QuoteNow it reads, with Q1 reversed:
Q1:
Gate: 6.14
Source: 0.65
Drain: 0.00
If the gate was actually the drain and the drain was the gate, the measurements would be good. But the pedal sort of worked like this. Pity Q2, 3 and 4 voltages where very odd. So we shall now attempt to lay the pin orientation problem to rest now.
Set your meter to the 2000 resistance test range. Place a transistor (let's call them FETs) on a non conductive surface, flat side up and the legs facing towards you. Place the meter's red lead to the centre pin and the black lead one of the outer legs. If the black lead is connected to the drain the meter will read anywhere between 150 to 650. If the black lead is connected to the gate the meter will show 1. Now move the black lead to the other outer leg and see what the meter displays.
Between the source and the drain the meter will show anywhere between 150 to 650. Between the gate and the source the meter should show 1. You have now identified the gate leg and which legs are source and drain. Now you may be wanting to identify which leg is actually source and which one is drain. There is no simple test for this and with these types of FETs you don't need to know. Why? Because with these types of FETS the drain and the source are transposable. It doesn't matter which way they are connected. Please note that this test only applies to this sort of FET.
If you are interested, place the black lead on the centre leg and then place the red lead onto the gate. The meter will now read around 1000. The device is a sort of diode so gate polarity does matter.
Check all the FETs out and see if you have any that are different. If you do, plug those back in to the BSIAB2 in the opposite direction. You can't hurt them in a low voltage unit even when incorrectly connected. But there is one thing that I think that you have noticed and that is once the unit has been running for a while (but still not working correctly) the unit will start to fail badly and to get it to work again, you have to unplug it and let it cool down. That is actually what you are doing - letting it cool down. Depending on the amount of current flowing in the FET junction (when incorrectly installed), the junction will heat up and stop working. There usually is no damage from this but it can happen, so be aware of this.
See what you find and good luck.