DIYstompboxes.com

Hello, this is my first post and I'm only working on my second pedal kit so it's going to be amateur hour.

I'm building a phase 45 clone with a univibe mod (same as stock but replace 2 caps) from a GGG kit. Here's the link: http://www.generalguitargadgets.com/effects-projects/phase-shifters/mxr-phase-45/

I've built it, inspected for shorts, cleaned up some solder joints, etc. but it's not working right. I get normal clean sounds on bypass, but when I activate the pedal I get ridiculously loud oscillating feedback. It sounds like a theremin or Moog, so it's got a vibey sort of sound, but that happens even with no play on the guitar and it's so loud that you can hear it when the amp volume is at 1. When I did one long test (which scared the hell out of my dog), the battery started to get warm so I stopped. On bypass it totally goes away.

GGG has listed the voltages for pins at the ICs and trannies. I've tried testing the voltages but this is totally new to me. I tested with red lead at these points with battery in, black lead in or on the enclosure. I couldn't get any voltage readings here, although the meter perfectly picks up the 9V battery difference. If I put the black lead on the negative side of the 9v battery and I was able to get voltages.
With that, I get for both IC1 and IC2: Pins 1 through 7 =7v, Pin 8 = ~9v

For Q1 I got 0 7 7 (sorry I am not sure which lead is gate, emitter, etc.) and Q2 I believe was 0 8 8 0 but I can't be sure because I couldn't see it perfectly as I was balancing the leads.

I am thinking that there is a short or maybe a grounding problem, but I'm at a loss to find it. I think the wiring is all right, but I'll check yet again. Does anyone have any other suggestions? Also, if you have corrections on the voltage measurements, pls. let me know. Thanks in advance for your help. I hope to pay it forward as I learn more.

If you can post pictures, that always helps.

OK now I feel like a real idiot, but when I hit the attachment button
I just see "img/img in brackets

AFAIK you have to host the pictures at another site.  I use photobucket, then copy the "IMG" link they provide, paste in thread post.  There are probably simpler hosting sites to use.

OK, here are links to some pics:

https://drive.google.com/open?id=0BxlQwqVFZmffQk5HMHY2UzN6TjdGTWFsNXNDMm8zOGVBSy1R
(//)
https://drive.google.com/open?id=0BxlQwqVFZmffOVozSmJTa00zMnUxeEdYMDZiSnVxWFQ4UnJZ

https://drive.google.com/open?id=0BxlQwqVFZmffZnFER05UTkpMYWtiZnBxTWhpWWZDQzNFWG1j
(//)
https://drive.google.com/open?id=0BxlQwqVFZmffUHVFR3ZkWk9rMmNCRUpvdzVCX0V1OEI1NHow

That way works too.  With the voltages you reported, I expected to see a bunch of bridged IC pins, but not really seeing that.  The first pic of the foot switch is pretty blurry, but (no offense!) the soldering looks a little rough.  Doubt that's related to the voltage results your getting.

I'll step aside and let the more knowledgeable folks chime in.

I realize that google makes you log in for those links. I'll get on photobucket tomorrow. And yeah I'm very new to soldering. The PCB joints aren't bad, it's more the wires that are tough, esp. with wires that tend to come apart after you put it through the lug or terminal.

I didn't have to log in.

> I didn't have to log in.

Google login is getting pretty sticky. I haven't used it in a while, but when I hit cns' links I got the face of my dead dog in the upper corner, showing Google remembered me (my IP? my PC? my browser?).

Doesn't seem to be remembering me.  I never stay signed in to anything, Firefox is set up to dump history and cookies when closed, and I don't store any passwords.  I see OP's posted pics and a "Sign In" button at the top right of the page.  YMMV, yadda yadda yadda.

I would say you have shorts or bad connections.  All your ground points should be 0V.  All your power (to ICs) should be 9V.  All other pins are likely to be pretty much right in between - so around 4.5V.  Carefully check your soldering and carefully check continuity for all those places you expect to be connected.

P.S. When you solder wires to the board, twist the ends together and solder them.  Now poke through the board: they won't unravel.  Finally solder your joint.

I have checked continuity and it was fine across all points on the same path but I might have missed some, so will check again. I haven't checked for continuity between points on different lines, but there are a lot of possible connections so that will take a while.

Offhand, is there anything in particular that would be expected to cause a ridiculously high output oscillating feedback even with minimal input signal?

Also, w/r to the voltages, I might not be doing them correctly because this is new to me. I put the black lead in one of the enclosure screw holes which I assumed would be ground. Does that sound right? If it is, then would my failure to measure voltages on the circuit mean that somehow current is going throuhg the enclosure?

apologies in advance if these are lame questions, I am really new to the world of circuits. Thanks!

OK my friend helped me figure out what I was doing wrong with voltages. Here are the voltage readings he got for the ICs and the transistors. I think they are fairly close to what they list at the GGG site:
http://www.generalguitargadgets.com/pdf/ggg_p45_instruct.pdf

Does this help to narrow down the problem?

IC1:
4.08
4.03
3.76
0
3.94
4.06
4.04
8.59 (full voltage of battery)

IC2:
3.87
3.95
3.94
0
5.49
1.70
7.97
8.58 (again, this is equal to full battery voltage.


Q1
1.6
3.94
3.94

Q2
1.59
3.94
3.94

> IC2: pin 7 = 7.97

I think IC2b pin 7 is stuck high. Normally it slams 1V to 8V and back, constantly, so a meter will give a wobbly reading in the 3V to 6V range.

Examine the IC2 pins 5 6 7 area, and the connections to the Speed pot.

> Q1 Q2 Gate = 1.6

These should change with R26 TRIM pot setting. I would expect better result with FET Gates above 2V, maybe 3V. However if IC2b is stuck, the FET trim is moot.

> IC2: pin 7 = 7.97
>I think IC2b pin 7 is stuck high. Normally it slams 1V to 8V and back, constantly, so a meter will give a wobbly reading in the 3V to 6V range.
>Examine the IC2 pins 5 6 7 area, and the connections to the Speed pot.

This is great advice, I will check it out! So I forgot to mention, voltage on IC2 pin 6 was wobbling, but it would settle on 1.70, so the actual voltage might be oscillating.

In terms of examining the pins, what am I looking for? should I resolder those points? I don't think there are any solder bridges, but of course, I can check again. Is there anything else I should look for in that area?

Hello, I took a break to see if I could come back with a fresh perspective. I've definitely cleaned up some bad joints, but there is still feedback. Oddly, with a DC power input and only output cable to amp, the pedal still produces feedback when switched on. This means that, somehow, the power input leads to feedback oscillations that are going to the output, right? The frequency of feedback goes higher when there is an input but either way it's loud. Moving the PCB doesn't have any effect, so I don't think it is a bad wire connection (though I will continue to look at them).

Does anyone have any ideas of what could be happening? Thanks! :-[

Did you check the soldering on the 3PDT switch? Looks like there is a little lead shunting two poles of the middle switch.

Have you tried to swap the two op-amps? Maybe the oscillations change then. If it does one of the op-amps is damaged.

Hope you can fix your pedal soon ;)

**I am feeling a little dumb. It does not generate feedback if there is only output. It requires something to be plugged into the input line.

>Did you check the soldering on the 3PDT switch? Looks like there is a little lead shunting two poles of the middle switch.

Yes, I just re-did the wires and I re-did any joint that looked wonky (successfully built a pedal in between so my soldering technique has improved!  :icon_mrgreen: ). It's much prettier now, but still generates feedback  >:( I can post updated pictures if it's useful to troubleshoot.

>Have you tried to swap the two op-amps? Maybe the oscillations change then. If it does one of the op-amps is damaged.

NO I haven't tried that. Are you saying that it might change the frequency of the oscillations?
>Hope you can fix your pedal soon ;)
THANKS for the support.

@M.A.P. I tried switching the ICs but there was no change in the oscillation frequency.  :icon_cry: There was some change in the feedback frequency when I moved the PCB up and down, but I could not localize the change to any particular wire. It does look like power goes out when I move the battery cable around (probably a cold solder joint from the battery cable to the DC jack), but that seems to be separate from the feedback issue. Another piece of info I forgot to mention is that if I play guitar through the pedal, the feedback oscillation is replaced by a fizzy, fuzz guitar sound. So inputs do go through the pedal, but it's clear that there is something wrong with the circuit that is causing the feedback and distorting the input signal.

I'm going to try more diagnostics tomorrow, but if y'all have ideas, pls. let me know.

Ok this is getting tricky :icon_confused:

I've checked the orientation of the poled caps, the FETs and the diode with your pictures and everything looks perfect. I think you really have a problem with one or more cold solder joints.

Take some time and redo all solder joints. That would be the next logic step I would take.

I once swapped all caps and transistors of a pedal that was faulty. I redid all solder joints and checked everything. But the pedal was in perfect condition! It was a low battery that cutted the signal like a low pass filter :icon_evil:

EDIT-THE READINGS BELOW ARE OFF. The only relevant point from this post is "When I put the voltmeter probe on IC1 pin 3, the feedback (and all sound) stops," but I haven't re-checked this.

IGNORE THIS:
So I got together an audio probe (I cannot believe how much I've picked up since March), and this led me to focus on pin 3 of IC1. I redid some joints and re-tested, and it is still generating feedback, although the sound is a little different. The voltages also changed a bit, I think. Note that I used an analog voltmeter for this, so the readings might be off by up to .5 volts based on my eyesight. :o

Here are my rough readings:
IC1:
4
4
.5
0
3.5
3.5
3.5
9

IC2:
4
3.5
3.5
0
1
1
oscillating between 2.0 and 7.0
9

Q1=0 3.5 3.5; Q2= 0 3.5 3.5

One last, probably useless factoid: When I put the voltmeter probe on IC1 pin 3, the feedback (and all sound) stops.

Any help is much appreciated, I really feel like this is getting closer to a fix. Thanks!  :)     
p.s. also I'll post updated photos.

Here are the photos:
(http://i1378.photobucket.com/albums/ah90/Ch_Ra/12998548_1023670491021664_8467196124606847097_n_zpsbdytdsmx.jpg)
(http://i1378.photobucket.com/albums/ah90/Ch_Ra/13007364_1023670481021665_5925277628240900194_n_zpsbhjzp31k.jpg)
(http://i1378.photobucket.com/albums/ah90/Ch_Ra/13001054_1023670511021662_1330404193755397168_n_zpsvgufyuva.jpg)
(http://i1378.photobucket.com/albums/ah90/Ch_Ra/12990863_1023670517688328_6335790490855016669_n_zps90mzwaxy.jpg)

Whats going on with pin 3 ic1?
meter loading?
Bad connection to Vbias?
Have you tried a continuaty test between R3 and pin 3?
The odd thing is even if R3 has a bad connection I'd expect that pins 2 and 3 would be similar because of the R2 no?
Maybe check for cold solder joints too.
Have you tried setting the trimmer?
Just thinking out loud.

Look at R29- it appears to be soldered in the wrong hole (its going to S3, not the LED anode)

Edit- maybe not, hard to tell, but check the orientation of the transistors (if they are not 2N5952 with DSG orientation)

OK I re-checked with my digital multimeter. I apologize for confusion, some of the error was probably due to the crappy voltmeter, but even across separate dugital multimeter readings I got some different results. This fits because, when I used the audio probe, a pin that gave feedback at one point would generate a fizzy hiss at other times.  >:(

Anyway, here are updated #s:
IC1: 4.25  4.2  3.86  .6-1.0 (inconsistent)  3.9  4.15-4.2  3.7-3.8  9.49
IC2: 4.04  3.9  4.04  .6 to 3.0 (random oscillations)  .6-4.0 (osc) 3-6 (osc)  1.6-3.0 (osc)  9.49
Q1: 1.3-1.9 (osc) 4.04  3.90
Q2:1.4-1.7 (osc) 4.04  4.04

@Cozybuilder:If I understand your question then I think R29 is correctly placed. There is continuity between it and the "L" wire. The transistors are oriented with the outline on the PCB. From what I understand, they used to have the transistor layout backward, but apparently, in the new version, the PCB outline is correct (though I think he says you can experiment with switching it).

@Kipper 3:

Quote from: Kipper4 on April 16, 2016, 04:31:56 PM
Whats going on with pin 3 ic1?
My analog voltmeter reading was off. I dk why, but readings are now around 3.86
meter loading?
Bad connection to Vbias?
sorry I dk what you mean. Can you explain vBias and meter loading? I'm really green  :icon_mrgreen:
Have you tried a continuaty test between R3 and pin 3?
I checked, and there is continuity
The odd thing is even if R3 has a bad connection I'd expect that pins 2 and 3 would be similar because of the R2 no?
I'm really sorry about the earlier readings, now the are closer. From my limited understanding, the schematic would suggest that you have to cross R3 and R2 to get from 3 to 2. Is that wrong?
Maybe check for cold solder joints too.
I've redone a lot of the joints, but I will check again.
Have you tried setting the trimmer?
Yes, trimmer changes the sound a bit but it doesn't eliminate feedback

One addendum: With the audio probe, I found that if you follow the schematic all the way from input-->C1-->R1-->IC1a Pin3-->Pin1-->direct to R10-->C4-->Output, that is the line where the feedback and noise is most noticeable. There is some noise and FB in other parts, but that track is the one with the most consistent and loud feedback on the probe.

The line is relatively clean from C3->Q2->R26;C6->R15->R18-R25->R20,R27, etc.

A couple of relevant points that might have been lost in this thread:
- This build has the Univibe mod, which means that Caps C2 and C3 had a 10 to 1 value ratio: a 0.1uF and 0.01uF cap
-The feedback is incredibly loud and thick, suggesting that gain is going out of range
-With audio probe, feedback is present both at the input jack and the output jack. Also, if I just run a cable from amp to input jack, no other cables, you get the feedback. I'm guessing this isn't supposed to happen, right?  :-\ What could cause feedback to work backwards to the input jack?

:icon_idea: Could the feedback reflect:
-a bad op-amp?
-something wrong with the op amp feedback loop like R4? (got this from a page at "op amps for dummies")
-a problem with capacitor C4?

When was this mentioned


"This build has the Univibe mod, which means that Caps C2 and C3 had a 10 to 1 value ratio: a 0.1uF and 0.01uF cap"

Where did you find this mod please?
if c2 and c3 values are 47nf how does a 10:1 ratio translate to 100nf and 10nf?
my maths aint that great.....
schematic
http://www.generalguitargadgets.com/pdf/ggg_p45_sc.pdf

Your audio path is IC1a,IC1b,IC2a.

IC2b is an low freqauncy oscillator.
and goes to the audio signal path through the transistors Q1 Q2
stick your audio probe on the no7 pin and turn the speed knob and you should hear the freqauncy shift.
This will tell you if your LFO is working

@Kipper4: Yes it is confusing. The caps that JD sent were indeed 0.1uF and 0.01uF, not 47 as in the stock schematic. The cap values are taken from the mod suggested by GGG: http://www.generalguitargadgets.com/pdf/ggg_p45_mods_instruct.pdf

I linked to the stock schematic that does not show the mod. I didn't think it would be helpful to link to the modified schematic because it shows all three mods and is much more complicated than the Mod1 circuit which just changes cap values. Obviously it would've been helpful to be more clear about this mod  :icon_redface: Here is the schematic w/all mods if it helps: http://www.generalguitargadgets.com/pdf/ggg_p45_mods_sc.pdf

Quote from: Kipper4 on April 17, 2016, 01:00:07 PM
IC2b is an low freqauncy oscillator.
and goes to the audio signal path through the transistors Q1 Q2
stick your audio probe on the no7 pin and turn the speed knob and you should hear the freqauncy shift.
This will tell you if your LFO is working

This is useful to know. I know that on the voltages, IC2bPin7 oscillated between 1.6-3.0V. I will check how this translates to sound.

Q: Is there any possible reason why feedback would go through input jack as well as output? (or am I doing something totally wrong in diagnostics?)  

Your voltages all seem to check out.
Someone said all the parts seem OK.

Look at R10 it's a negative feedback path from the output of all three op amps.

Can I just ask again.
When you plug your guitar in the input and amp at the output.
What does it do?
Does it sound phaser like?
Does it sound like a weak univibe?
Or just pure feedback loudness?

Sorry to appear so curt. I don't get why I wouldn't work if everything seems in order, and I really want it to work for you.

Quote from: Kipper4 on April 17, 2016, 02:30:15 PM
Look at R10 it's a negative feedback path from the output of all three op amps.

I checked the resistance on the multimeter and it came out right, but should I try to resolder that one just in case?

Quote from: Kipper4 on April 17, 2016, 02:30:15 PM
Can I just ask again. When you plug your guitar in the input and amp at the output. What does it do? Does it sound phaser like? Does it sound like a weak univibe? Or just pure feedback loudness?

I haven't tested it with a real amp in a week or so (because I couldn't take the noise!) but when I tested it on an amp, it sounded like Thor playing a Moog  :icon_razz: There was a thick oscillating sound when no guitar was playing. When I played the guitar I could hear it but it was fizzy, like as if it was going through a fuzz face but at a very low output relative to the feedback. So there was something along the lines of a phase/vibe sound, I think.

Quote from: Kipper4 on April 17, 2016, 02:30:15 PM
Sorry to appear so curt. I don't get why I wouldn't work if everything seems in order, and I really want it to work for you.

Hey, I totally appreciate your taking the time to help. JD Sleep actually offered to check it out if I sent back to him, but I've put so much time in, I really want to figure this out on my own (well with your help!)  ;)

Also, I'm sorry I have been reporting inconsistent information, but I am new to multimeters, audio probes, etc. This is only the second pedal I've built and before these builds, I had virtually no electronics experience. So I'm learning a lot through this process and from your feedback. Thanks! 

@kipper4: n.s. if this helps but when I probed the line of resistors below the R10 feedback line, I got fizzy noise from R5-R7, but past R7 it was *relatively* clean.

Is it possibly that you fried the fets with soldering.
No offence and I can't see too well but the solder looks a bit blobby on the fet legs.
Have you got spare fets and some sockets you could try?
While you have the meter out. What value is R1 on ohms setting?
Sorry to keep asking silly questions...

Quote from: Kipper4 on April 17, 2016, 04:57:50 PM
Is it possibly that you fried the fets with soldering.
No offence and I can't see too well but the solder looks a bit blobby on the fet legs.
Have you got spare fets and some sockets you could try?

Not offended, it's possible. The FETs are Q1 & Q2, right? Q1 to my eye looks ok but Q2 is a little blobby.  I did install the FETs and ICs after other PCB components in order to minimize heat damage, but it's possible that they got burned.  I don't have anything to test them, and unfortunately, don't have spare FETs or sockets. Would it make sense to resolder Q2?
Also, do you think the voltages are consistent with fried FETs? It looks to me like the Gate voltages might be off but the instructions say "2.2V plus or minus some".

Quote from: Kipper4 on April 17, 2016, 04:57:50 PM
While you have the meter out. What value is R1 on ohms setting?
Sorry to keep asking silly questions...

9.98K which seems to check out with the schematic. Is it just me or is this maddening? But please keep the questions coming!

Does it still change the sound if you physically move things around like battery wires and knobs? If you connect an output cable ( but not to anything at other end) does it change the sound at all via the audio probe? My gut on this would be a trim pot out of alignment or a short/open somewhere.

And just for kicks, is everything that is supposed to be at ground really at ground? With power off, check for continuity from case to battery negative, wiggle the wire to make sure. Then move on to check around for things that should be at ground, especially the ground pins in the ICs. Another thing is check that the IC pins have a good connection through the board. I think this may seem very basic and you probably already did most of this. But sometimes it's easy to overthink a problem. gl

my turn to be rude. what part # do you think your fets are? and what part # is marked on your fets? (it pays to play this game sometimes.)

also, as RtQ suggests - get a resistor leg cut-off or something similar, and poke into each pin of your IC sockets in turn. it sometimes happens that socket pins don't actually contact the IC legs.

Thanks guys for all the ?s, suggestions. Pls. see below:

Quote from: robthequiet on April 17, 2016, 11:49:35 PM
Does it still change the sound if you physically move things around like battery wires and knobs? If you connect an output cable ( but not to anything at other end) does it change the sound at all via the audio probe? My gut on this would be a trim pot out of alignment or a short/open somewhere.

-Yes, the pitch and oscillation frequency would change when I moved wires around.
-For the audio probe test, do you want the audio probe positioned at the output jack when I pop in the output cable? Also, last I checked the pedal would not power on w/o input cable, but that was with the battery, it might switch on w/9V adapter
-When you say trim pot out of alignment, do you mean that it needs to be adjusted? I tried adjusting the trimpot across the whole range, and although sound changed, feedback was still there. Also, when I checked w/audio probe, points at trim pot were clean.

Quote from: duck_arse on April 18, 2016, 11:20:36 AM
my turn to be rude. what part # do you think your fets are? and what part # is marked on your fets? (it pays to play this game sometimes.)

-Given that your handle is duck_arse, this is not at all rude ;)
-Good idea: I believe it is 2N5485 (I ran to the garage to check w/a magnifying glass, and after returning, my memory is a little vague. Aging sucks.) The bill of materials and schematic say: 2N5952. According to the GGG instructions:

Quote"The kit comes with a great sounding set of matched 2N5485 transistors.
The original units had 2N5952 JFET transistors. Note that the pin out of these
transistors may very. The 2N5952 will probably have to installed backwards from
what the layout shows.

@RTK:

Quote from: robthequiet on April 17, 2016, 11:54:57 PM
is everything that is supposed to be at ground really at ground? With power off, check for continuity from case to battery negative, wiggle the wire to make sure. Then move on to check around for things that should be at ground, especially the ground pins in the ICs. Another thing is check that the IC pins have a good connection through the board. I think this may seem very basic and you probably already did most of this. But sometimes it's easy to overthink a problem. gl

- At my level, I'm not sure I'm capable of overthinking it :)
- ground wire for battery cable is currently disconnected (it broke during other tests, but feedback was there before anyway) but ground points at jack, switch, PCB terminals, and pin 4 of both ICs show continuity with the enclosure. Now when I checked voltages I found a small, oscillating voltage at pin 4 at IC1a and 2a. About .6 to 1v but up to 3.0 at times. 
-Good idea with IC pin continuity. To check I ran continuity from pin on IC to socket solder joint. All of them checked out.

@duck_arse:

Quote from: duck_arse on April 18, 2016, 11:20:36 AM
also, as RtQ suggests - get a resistor leg cut-off or something similar, and poke into each pin of your IC sockets in turn. it sometimes happens that socket pins don't actually contact the IC legs.

-sorry to be dense, but when I poke the IC socket what should I look for? Continuity? Would the test I described above address this?

My curiosity about the sound changing when you wiggle wires and adjust the trimpot etc. is to make sure that the components are physically OK. The fact that you hear some guitar signal is actually a good thing. Without hearing what's going on, my next question is: If you connect guitar and amp (with volume not too loud) and apply power, does the sound change if you adjust the speed pot?

And if you set the device down and take a toothpick or some such non-metallic object and gently tap on various components to see if something might be loose, that might give us a clue.

I think you already checked the legs of the jfets to make sure they're in the right hole... 

Hm, and if everything goes dead if you put a meter lead on pin 3 of one of the ICs, is it shorting against pin 4 and taking evrything to ground?

Back to overthinking things, if the LFO circuit has a kink in it somewhere it might be acting not as a low freq oscillator but as a full blown audio freq oscillator, and the signal somehow radiating into the circuit. So I would make sure that everything about pins 5,6,7 & 8 of IC2B is happy, along with what is happening at the base of Q1 and Q2. Carefully, though, when the circuit is alive. If I'm reading the schematic correctly, you should get a very slow change in voltage at the base of each jfet that would be readable with a voltmeter on DC voltage. I would take the readings not from the actual transistor leg but from where it connects to another component, i.e. at the junctions of R17/C5 for Q1, and R18/C6 for Q2.

Please let us know what you find, and kudos for sticking with it!

the leg pokings - the idea is, sometimes the IC pin sits in the socket pin, but the socket has gorn loose, or is carp to start, and there is no actual electric connection being made. so, you get a skinny wire, and poke it into that gap you can see between the round of the socket and the flat of the IC pins, and see if the overall operation changes. if it does ......


.... and so you know you need to check the part # of the fets and their datasheets for pinouts, rather than just plug them in and solder, yes? yes.

Just wanted to let you know I'm still on the case, but have been working my day job and have not had time to run tests suggested by RTQ and DA. Will get back on this when I can play hookey at lunch :)

OK, so this AM I resoldered some joints in which there was a ball of solder on the top of the board. AT this point I think everything has been resoldered and some maybe a few times. the solder joints now all look good (i think) but the PCB is not pretty my friends ;)

Quote from: robthequiet on April 18, 2016, 02:42:12 PM
My curiosity about the sound changing when you wiggle wires and adjust the trimpot etc. is to make sure that the components are physically OK. The fact that you hear some guitar signal is actually a good thing. Without hearing what's going on, my next question is: If you connect guitar and amp (with volume not too loud) and apply power, does the sound change if you adjust the speed pot?

Answer: I re-tested after all the resoldering, and this time, I could not hear the guitar. But it's possible that I just couldn't hear it over the feedback. Sadly, there is still feedback and The gain is still absolutely ridiculous--at volume=5%, it cranks at speaker-blowing volumes, so that makes extensive amp testing difficult. Tt appears that feedback tone changes depending on input/output. If I only connect amp cable either to input line or output line feedback is low-pitched (yes I get feedback from both in and out jacks). If I connect instrument line to input jack and amp to output jack, feedback is noticeably higher in pitch (but still relatively low) and it still sounds vibe/phasey and synth like. Speed pot indeed affects oscillation speed as expected. Moving around the PCB affects the feedback pitch, and sometimes it affects depth of vibe/phase oscillation but feedback is continuous (except if bottom of PCB touches and shorts to enclosure).

Quote from: robthequiet on April 18, 2016, 02:42:12 PM
And if you set the device down and take a toothpick or some such non-metallic object and gently tap on various components to see if something might be loose, that might give us a clue....Hm, and if everything goes dead if you put a meter lead on pin 3 of one of the ICs, is it shorting against pin 4 and taking evrything to ground?

-I re-checked voltages and readings are:
on IC1a: 4.0 4.0 3.82 .6 IC2a: 4.0 4.0 4.0 .6
-Yes, it looks like everything goes dead when I short to ground, and that happened when lead shorted pins 3-4  :icon_redface:
-So I did not get any effect of tapping most of the components with a pencil. There were some weird changes in feedback when tapping in zone of Q 1 but I could not replicate them consistently.

About pins 5-8, what does it mean for them to be happy? Should I be checking for continuity? There aren't any useful voltage references for IC2b, but I can certainly check voltages at IC1b. I'll also check for very slow oscillation at JFET base, though I might get some false alarms because my hand is not steady :(

Basically "happy" means everything connected soundly, so my test for signals or voltages at _junctions_ would possibly reveal a clue, as in does each component have connectivity across the trace. HM, so it sounds like you've built a really great oscillator. I'm going to toss out a suggestion that should be taken with a grain of salt and maybe corroborated by a couple of experts, but if it were me I would de-solder and disconnect all jacks and switches, including battery cables, clean everything up and reassemble after inspecting everything with a magnifying glass. I get the feeling that the components are mostly OK if you get some response from the controls. The change in pitch as you plug in input and output is interesting, although most circuits will radiate signals here and there which can be affected by objects moving around. My thinking is that the audio and LFO are secretely co-mingling so maybe a resistor or cap is bridging through a solder blob. Yup, the magnifying glass would be my preferred tool at this point, before even applying power.

If I were you I'd replace Q1, Q2 and just to be sure also IC1 and IC2.

If you're sure all the solder joints are ok and all the connections between the jacks, 3PDT switch and PCB are done right you must have a broken semiconductor device. To be sure it's one of the JFETs you could use your audio probe and check IC1 pin5 and IC2 pin 3. They're connected to the JFETs. You should have no oscillation on IC1 pin 3 when nothing is connected.

Just to be sure you could recheck the wiring of the potis, jacks, switch etc. I had issues with one pedal of mine and when I looked closer I saw that the ground connection from the jacks to the pcb was missing :icon_rolleyes: :icon_redface:

@RTQ, you mentioned IC2b and base of Q1 and Q2. The layout says "D S G" for pins of FETs. novice ?: is base=S? Q1 rapidly oscillates at G from 1.2-1.5ish. S is solid at 3.99ish. I get inconsistencies on D pin some times it oscillates very slowly and others faster in 3.9 range, others it slowly veers between 3.99-4.0 the variability might be due to my unsteady hand, but worth thinking about. Connections are consistent with these pins. at Q2 it's 3.8-3.9, 3.98, 1.4-1.8 (D S G) and it looks like connections are consistent. I need to re-check actual voltages 5-8 of IC2b, because the rapidly changing numbers were giving me a headache but they looked consistent with connected nodes.

Gotta get back to day job and band practice tonight but will attend to other sggestions when I can.

Good catch... the equivalent of the base is the gate -- my bad -- so if I'm looking at the same schematic, looks like the LFO is doing it's thing as expected. The gates of Q1 & Q2 should pretty much be the same, and under the control of R26 and R27.

Looking at the fets, I might double-check orientation -- the datasheet at https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwihj82eqJ7MAhUF9h4KHfu9DV0QFggdMAA&url=https%3A%2F%2Fwww.fairchildsemi.com%2Fdatasheets%2F2N%2F2N5952.pdf&usg=AFQjCNGmjZWDtFgAA0NAfXWjbHJozjeDdQ&sig2=FnbZyEZUxniSrwX7vEt1_A&cad=rja (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwihj82eqJ7MAhUF9h4KHfu9DV0QFggdMAA&url=https%3A%2F%2Fwww.fairchildsemi.com%2Fdatasheets%2F2N%2F2N5952.pdf&usg=AFQjCNGmjZWDtFgAA0NAfXWjbHJozjeDdQ&sig2=FnbZyEZUxniSrwX7vEt1_A&cad=rja) is confusing me a bit.

New idea, when you plug in your instrument, can you verify that the on-off switch actually disengages the bypass? If it was "on and off at the same time", it might create a feedback loop visible at both ends. Just a guess... Oh, and does the screaming stop if you activate the switch S1? And does the LED turn on and off? Sorry if you've already looked at this, and I don't mean to be snippy in any way, please feel free to disregard anything that might seem obvious or irrelevant. GL!!

@rtq: running to band practice, but very quickly, how can I verify whether: "the on-off switch actually disengages the bypass" or whether it was "on and off at the same time"?

Hey, sorry I didn't catch you earlier -- essentially, the switch will bypass the effect when you click it "off". At that point you should get nothing coming out of the box except for the guitar and the LED should turn off. If you're getting something other than guitar in both "on" and "off" there is probably a crossed wire somewhere. If the squealing is always there no matter what the switch does, that would be "supporting evidence." If I'm reading the schematic correctly, the guitar should come through if the switch is "off" even if there is no power to the box. HTH!

Quote from: robthequiet on April 21, 2016, 01:50:45 AM
Hey, sorry I didn't catch you earlier -- essentially, the switch will bypass the effect when you click it "off". At that point you should get nothing coming out of the box except for the guitar and the LED should turn off. If you're getting something other than guitar in both "on" and "off" there is probably a crossed wire somewhere. If the squealing is always there no matter what the switch does, that would be "supporting evidence." If I'm reading the schematic correctly, the guitar should come through if the switch is "off" even if there is no power to the box. HTH!

@rtq: confirmed bypass works. clean guitar sound w/bypass on, even when pedal power is disconnected. Loud feedback when engaged. In earlier test I kept amp super low because even at zero volume the feedback is loud and that is why I couldn't hear guitar. When I turned it up today, I could actually hear faint fizzy guitar amidst the siren-like feedback. This is consistent with audio probe test run earlier.

Quote from: M.A.P on April 20, 2016, 03:25:44 PM
If you're sure all the solder joints are ok and all the connections between the jacks, 3PDT switch and PCB are done right you must have a broken semiconductor device. To be sure it's one of the JFETs you could use your audio probe and check IC1 pin5 and IC2 pin 3. They're connected to the JFETs. You should have no oscillation on IC1 pin 3 when nothing is connected.

Just to be sure you could recheck the wiring of the potis, jacks, switch etc. I had issues with one pedal of mine and when I looked closer I saw that the ground connection from the jacks to the pcb was missing :icon_rolleyes: :icon_redface:

@M.A.P. -thanks for this advice. I will re-check the connections. Speaking of 3PDT, is it possible that some failure or defect in the 3PDT switch could cause a problem like this?
-So are you saying that I should check IC1 pin5 and IC2 pin 3 when there is no line input plugged in? Or when the pedal is turned off or when there is no input or output whatsoever? 
-It is good to know I am not the only one who has done such things :)

Hm, I might try swapping the opamp ICs between sockets to see if it makes any difference. I think you already tried this, though. If one chip was blown I would expect a change. I'm leaning towards what M.A.P is suggesting and looking at possible faulty FETs. Or revisit the previous quote,

Quote"The kit comes with a great sounding set of matched 2N5485 transistors.
The original units had 2N5952 JFET transistors. Note that the pin out of these
transistors may very. The 2N5952 will probably have to installed backwards from
what the layout shows.

Depending on who made the FETs and which part they are, you might have a reversed gate and drain which would definitely cause misbehavior. These instructions do not inspire confidence. I think they meant that the 5485 would have to be installed backwards from the 5952, so don't necessarily go with the layout.  :icon_rolleyes:

Quote@M.A.P. -thanks for this advice. I will re-check the connections. Speaking of 3PDT, is it possible that some failure or defect in the 3PDT switch could cause a problem like this?
-So are you saying that I should check IC1 pin5 and IC2 pin 3 when there is no line input plugged in? Or when the pedal is turned off or when there is no input or output whatsoever? 
-It is good to know I am not the only one who has done such things :)

Exactly. Check the IC pins when there is no input signal, no output connected and power on. Maybe you have to solder a link at the input jack for the connection of the battery with the circuit ground. The FETs are driven by the LFO in the right corner of the schematic. You could also check IC1 pin 3 and IC2 pin 7. Or just to be sure you could check all the pins with the audio probe and write down on which one an oscillation can be heared.

I don't think that a broken switch would create an oscillation. But never say never ::)

Quote from: M.A.P on April 22, 2016, 10:22:51 AM
Exactly. Check the IC pins when there is no input signal, no output connected and power on. Maybe you have to solder a link at the input jack for the connection of the battery with the circuit ground. The FETs are driven by the LFO in the right corner of the schematic. You could also check IC1 pin 3 and IC2 pin 7. Or just to be sure you could check all the pins with the audio probe and write down on which one an oscillation can be heard.

Done. So, with DC in, pedal powers up w/o input. There was no oscillation with the probe, just increased static. I checked again with an input, output, or both, and feedback comes back. Heres the weird part: If I have both inputs and then pull 'em out, running the audio probe on IC1a pin 3 still elicits feedback for as long as I want. But then if I touch one of the other pins, the feedback goes away and touching pin 3 again just gets static from the audio probe. In other words, there seems to be an after effect on IC1 pin 3, even after instrument cables are removed, but touching probe elsewhere makes the after effect go away.

Also, I had the battery ground hooked into the input stereo jack, as you suggested. There was no battery for these tests, though, so I'm not sure it would've made a difference anyway.

@RTQ, ok I can try switching orientation of the JFETs. I'm a little worried that resoldering the joint could damage them, but you think it's ok?
It was also suggested to replace the JFETs and ICs. I'd have to order them, which I can do. I've got a transistor testor coming in a few days, so thinking I'll test w/that before ordering new ones.

don't blindly reverse polarised parts. get the part # and manufacturers name/logo from the part, look the interwires for the datasheet. then compare the pinout shown on the datasheet to the board layout and the circuit diagram. if you don't know what it is you're looking at on the schematic, or don't understand the pinout diagram, just ask.

Quote from: duck_arse on April 25, 2016, 11:24:19 AM
don't blindly reverse polarised parts. get the part # and manufacturers name/logo from the part, look the interwires for the datasheet. then compare the pinout shown on the datasheet to the board layout and the circuit diagram. if you don't know what it is you're looking at on the schematic, or don't understand the pinout diagram, just ask.

Got it, that makes sense. I probably will need help w/the translation between the datasheet and the layout on the board, so hope you don't mind more questions :)

Yes, you may just have it right with the FET's, but the two part numbers in question hava a diffeent pinout. The datasheets have pictures. As a consumate nitpicker, I always triple-check these things. If, hat tip to duck_arse, you determine that you need to, de-soldering the FET's should not harm them as long as you're using a heat sink on the legs (i.e. an alligator clip or such, I use small forceps) and small needle-nose pliers. Definitely feel free to ask questions any time.

The nature of the sound changing (aftereffect) is fairly normal. By the time we're done this is going to be one tired but strong little box.

@d_a+@RtQ:
So I found the datasheet: https://www.fairchildsemi.com/datasheets/2N/2N5485.pdf
I believe that the orientation corresponds to the GGG layout and the transistor's orientation in the PCB. If viewed from the back/flat side (front?) first, G wire is on right hand side right wire, S is middle, and D is left.

Is this all I should check out? Is there other useful info in the datasheet that I need?

Well done mate. The 2n5458 seems to have the same pinout as the one in the ggg layout.
Now you know how to source the pinout and identify it form the data sheet.
From the same sheet you can compare the on and off characteristics. Etc.
Your on your way.

Thanks @Kipper4, good to know I am making progress  :)

To continue on the path: Do the on and off characteristics correspond to the voltages you would record when pedal turned on or off? Or are they absolute limits so if your voltage is higher then you know something is wrong?

QuoteTo continue on the path: Do the on and off characteristics correspond to the voltages you would record when pedal turned on or off? Or are they absolute limits so if your voltage is higher then you know something is wrong?

Pretty much true. Another thing I would check in general is current.

I am definitely not trying to send you on a wild goose chase with this, but what I would be doing is "walking the circuit" against the schematic, or layout. In other words checking with power off and the meter set for resistance (on "beep"  mode if available) to check for continuity from pin to pin between components. Tricky, of course, because some connections are common to multiple parts. But if you found something open where it should show a join it might be a clue.

I'm going back to look at the voltages and pics you got earlier to see what else they might tell.

that diagram of the TO-92 package is the way/the one to draw on all your diagrams whenever you use a TO-92. of course, it it was a TO-18 package, you'd draw that instead.

Quick questions before I continue:
-@rtq dumb question, but are you saying to run a continuity check or to test resitance b/w points. My multimeter has different settings for those two options, and continuity tells me "short" vs "open" and resistance tells me resistance in ohms. [as an aside, I've run a lot of continuity tests in a semi-systematic fashion. I can't say that I've checked all connections, but a lot]
-I have a transistor tester coming in the mail today. Is it worth desoldering the transistors to test them out? I suppose I can also use the probes to check them in the PCB.

Oh, what I do is set my meter on "beep" just to get a quick answer as to whether something is open or not. Hopefully the resistance across a short is zero so it's kind of moot :icon_cool: . Testing components for resistance in circuit is something I usually avoid, because everything is connected to something else. But what I'd be looking for is something that is not actually connected even though it seems to be OK visually. As far as pulling the FETs out, in this case I guess it wouldn't hurt given the mystery of the unit. Might give us a chance to microscopically examine what's going on with the circuit board in their vicinity. Good chance to install sockets in the process.

edit: PS Sockets might be useful if you think you might swap the FETs out for fresh ones, but as Mark Hammer said on another thread, it's more secure in the long run to solder them in, your call, of course.

Please repost your voltages. I can't remember if they where all ok or not.

Also does the circuit have a bypass switching arrangement already in place?
This feedback things bugging me. I'm sure it's not bugging me as much as the OP.

Does the circuit work without the switching?
Have you tried testing the circuit before you made the switching arrangement.

If there's an issue with the switch. It might possibly be causing the "feedback"

Sorry to ask. I know I'm a PITA.

 (http://www.olaolaonline.net/thumbs/20160428001530_mxr_phase_45_0001_tn.png) (http://www.olaolaonline.net/page.php?image=20160428001530_mxr_phase_45_0001.png)

I dismantled my previous p45 (which worked perfectly), and used almost all the components (ics and trannies, resistors and caps) to gave birth to a new one using this layout above, which is the one you find online but made it smaller to save 1 row and 1 column, and include univibe mod at the same time.

obviously, it doesn't work. signal pass, but no phasing...

mandatory voltages.
WW 8.86v
upper IC
1 3.79
2 3.83
3 3.82
4 0
5 3.82
6 3.83
7 3.86
8 8.86

lower IC
1 3.86
2 3.85
3 2.60
4 0
5 3.27 <-> 5.43
6 3.66 <-> 5.63
7 1.37 <-> 8.21
8 8.86

2n5458
3.82
3.82
1.58 <-> 1.75

Quote from: Kipper4 on April 27, 2016, 04:31:20 PM
Please repost your voltages. I can't remember if they where all ok or not.

Also does the circuit have a bypass switching arrangement already in place?
This feedback things bugging me. I'm sure it's not bugging me as much as the OP.

Does the circuit work without the switching?
Have you tried testing the circuit before you made the switching arrangement.

If there's an issue with the switch. It might possibly be causing the "feedback"

Sorry to ask. I know I'm a PITA.

1. OK I'll check voltages again. I just got a cheap transistor tester, so I'll also try to figure out a way to test them w/o removing them from the PCB.
2. Yes the feedback is bugging me even more. But thanks it's really cool that you and other forum experts have been sticking through this.
3. Does the circuit have a bypass switching arrangement already in place? I'm not 100% sure what you mean, but the footswitch is installed and it is wired for true bypass. The sound is perfect when bypass is on, but the feedback will go through both inputs and outputs when pedal is powered on. The gain is so high that you can hear it even with volume at or slightly above 0.
4. Right now I'm still early on the learning curve so, I did not test the circuit before installing the footswitch. Is there a way to easily test the circuit w/o switch that does not involve desoldering all wiring to the switch? I really cleaned up the wiring and I think I might cry if I have to undo all that work  :icon_frown:
5. I have been wondering if the 3PDT switch might possibly be causing the "feedback". Can you think of how a switch problem might do this? Is there a continuity test I can run to test for this possibility?
6. thanks Kipper, no you're not a PITA :)

Follow up:
So I got a cheap transistor tester today (http://www.ebay.com/itm/321963237498?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT) and tested the JFETs. I was nervous about desoldering them b/c I didn't want to damage them during testing, so I used some wires for leads to hook around the legs of the transistor on the PCB. As a result, these readings might be off. My tester said that Q1 showed 2.3A and 1.1V, and Q2 showed 3.2A and 1.0V. I don't know what the voltage and current correspond to on the datasheet  :icon_redface: and again I'm unsure of the readings. But I am guessing that these matched JFETs should show approximately equivalent numbers??

Voltages:
Q1 (D S G)= 3.92;   4.02;  1.4-1.7 [voltages on G seem to oscillate]
Q2 (D S G)= 4.01;   3.99;  1.3-1.7
IC1: 4.15   4.12   3.83   .6   3.9   4.06   3.87   9.11
IC2: 3.8-3.97   3.93-3.95   3.88-3.89   .7   0-5   0-5   0-8.5  9.13 

Your voltages seem to check out. And if the gates wiggling the lfo is working .great.
I'd unsolder the in out wires to board end and put temporary ones in and test it without the switch

Quote from: Kipper4 on April 28, 2016, 05:29:50 AM
Your voltages seem to check out. And if the gates wiggling the lfo is working great.

@Kipper, I just updated the voltages to include IC2 (see above). In the build instructions it says voltages for pin 4 of both ICs should be zero, but in all my tests, it has been pretty solid in the .6-.7 range. Is that weird or normal [I dk how to interpret these voltages]?

Quote from: Kipper4 on April 28, 2016, 05:29:50 AM
I'd unsolder the in out wires to board end and put temporary ones in and test it without the switch

I think I get it, but let me make sure. Right now wires go from "I" and "O" pads to switch. So you are suggesting that I remove those wires and remove connections b/w jacks and switch, so I can put a temporary wire linking jacks directly to I and O. Right? It makes me shudder to think of desoldering more connections  :icon_cry:, but I can do it in the name of science!

Another?: I feel silly having bought a transistor tester and not knowing what the results mean. Is it unusual that the current and voltage readings from the tester do not match across the JFETs? For that matter, when I see results about current, "HFE", and voltage, how do I know whether results are bad or good? Sorry for the lame questions, but I will learn!

The transistor tester I believe should be used on components out of circuit. Any other components attached to the legs would present other avenues for current to flow and skew the results. Also note the diff between testing FETs and BJTs, as I am fond of saying things that go without saying.

QuoteThe sound is perfect when bypass is on, but the feedback will go through both inputs and outputs when pedal is powered on

<---  This does raise a question about the switch, so I'm with Kipper4 on testing with switch out of circuit. In true bypass, the signal from the guitar completely disconnects from and goes around the box. So the bypass part works fine, it's when we stomp on the switch that the fun starts. I'm not big on adding solder joints, but you could just snip the wires at their mid-point and alligator-clip connections for testing the switch, then resolder and shrink-wrap them back together later. Saves the switch and board from desoldering trauma.

As far as pin 4 on each chip being at .6 or .7, that would coincide with the voltage drop across a diode junction, but could just be a coincidence. I would expect zero volts at ground, too. One way to look at that is to put the meter leads carefully on pin 4 and pin 8 of each chip, then try the same but put your leads on pin 4 and the ground side of the battery terminal. If the ground on the chip is not at circuit ground, that would be something to ponder. According to GGG, pin 3 on IC2 should "vary with speed control" -- does it vary or just stay locked on ~4V? A 0.2V swing may be normal, but imagine what happens if IC2 pins 2 and 3 were shorted?

Also,

If it's any consolation, my main axe is a strat that I've been tinkering with for 20 years. I'm reheating solder that came from the factory in 1991. Just have to heat sink the parts when you apply the iron.

Sorry for the double post!!

Quote from: robthequiet on April 28, 2016, 02:16:22 PM
As far as pin 4 on each chip being at .6 or .7, that would coincide with the voltage drop across a diode junction, but could just be a coincidence. I would expect zero volts at ground, too. One way to look at that is to put the meter leads carefully on pin 4 and pin 8 of each chip, then try the same but put your leads on pin 4 and the ground side of the battery terminal. If the ground on the chip is not at circuit ground, that would be something to ponder. According to GGG, pin 3 on IC2 should "vary with speed control" -- does it vary or just stay locked on ~4V? A 0.2V swing may be normal, but imagine what happens if IC2 pins 2 and 3 were shorted?

These are really good suggestions. Will follow up.

Quote
If it's any consolation, my main axe is a strat that I've been tinkering with for 20 years. I'm reheating solder that came from the factory in 1991. Just have to heat sink the parts when you apply the iron.

Sorry for yet another ?, but how do I heat sink the parts?

I know your reluctant to remove the I and Out wires.
It's just a hunch, based on your feedback comment.
Usually I test all circuits work before doing the bypass switching. Just one less thing to debugg. If I know the circuit works and I attach the switch and it no longer works, I'm all over that switch.
Next I box it up, it now doesn't work. Geez just an ordinary day at the bench. Start looking for shorts and stuff. Anyway you get the picture and if not here's a little saying we have around these parts.
Rock it before you box it.

Heat sink. Clamp the needle nose pliers, haemostat , tweezers what ever you have, to the leg of the transistor/componant your about to solder.
This will absorb some of the heat from the soldering and save the body overheating.
Maybe do A leg then do something else to allow it to cool a bit.
You shouldn't need to be too cautious. Get in with the iron heat up pad and leg, flow the solder and get out, a few seconds should be enough.

Let us know if you decide to test withou the bypass switching. And the results.

Rich

To heat sink or sink heat, clamp an alligator clip or forceps or tweezers on the leg, if possible between the component and the iron -- it serves to draw heat out of the component so that the component does not take all the heat from the iron. Right down on the board, it may not be possible, so use your needle-nose pliers on the component side and the iron on the copper side, and pull very gently. Using solder-sucking mesh could help to remove excess solder, but just to lift a leg of a diode or transistor, you only have to heat the join enough that the leg will come out with a very gentle action. I'm sure there's a couple of videos around on solder technique, hopefully something about heat sinks. Good skills to have if you go about salvaging germanium transistors from old radios and TVs.

Got it, thanks to you both!

So, I desoldered the I and O wired from the board. Then I did a quick and dirty solder of wires from the board to a couple of mono 1/4 inch jacks and ran a ground wire between them. Now I'm getting no sound. I certainly can fix the soldering job on the 1/4 inch jacks, but wanted to ask: Is it just better to wire the board directly to the original jacks on the pedal enclosure? I soldered to new jacks because I figured that all the extra connections to the switch, DC jack, etc. could mess up this experiment. But now I'm thinking that I might have been better off just replacing the in and out jack wires with the wires that I've hooked into the PCB. Thoughts?

Ok great. That's cleared that up.
Back to the circuit then.
I'll take another look through all through the info tomorrow as it's very late here now.
Ps you did have the fets in when you did the test didn't you?

Um, just to make sure that the ground is also connected to circuit ground. I would go right to the ground side of the battery.

 :icon_idea:

Quote from: Kipper4 on April 27, 2016, 04:31:20 PMDoes the circuit work without the switching?
Have you tried testing the circuit before you made the switching arrangement.

If there's an issue with the switch. It might possibly be causing the "feedback"

So, I successfully wired up temporary in and out jacks and added a common ground wire with alligator clip so we can ground to enclosure. I appreciate the suggestion, because I can totally use this to test circuits on future projects w/o hooking up the 3PDT.

....and now for the results [drum roll.........]

Kipper4 gets a slam dunk!  :D [thanks also RTQ and D_A, MAP and others who have chipped in!]
It is a clean, working phaser circuit. No feedback, guitar sound comes out phased/vibed, speed control works, etc. Effect is subtle, but it's clearly there. It feels so good to finally make progress!

So there was *something* about having the in and out running through the footswitch. Part of me wants to quit while I am ahead, and just box it. But I figure that this journey is not finished until I get it working w/a switch. At this point, what is the best way to diagnose the problem with the switch? Before I disconnected, the switch was able to toggle b/w bypass and effect. Is it still possible that the switch is somehow broken?

All of my previous continuity checks on switch wiring seemed to pan out, though I will re-check. One thing I noticed when inspecting switch wiring is that the switch wiring on the GGG layout differs a bit from the finished pedal wiring shown on the instructions http://www.generalguitargadgets.com/pdf/ggg_p45_instruct.pdf (http://www.generalguitargadgets.com/pdf/ggg_p45_instruct.pdf)

Any other ideas on what to check?

I suppose it's also possible that there was a problem with in/out jack wiring in the pedal enclosure, because now its working when I am using a separate pair of jacks.

p.s. you all are awesome. Thanks for the moral support and the suggestions.

What what what?
Its working. Excellant.
Myself and many others use the tonepad offboard wiring no 5.  http://www.tonepad.com/getFileInfo.asp?id=76
Be sure to note the direction of the lugs on the switch bottom.
I now wish I had one of those gif images to share that show how these switches work. Anyone.

I've effed up some switches in the past by too much heat, that warms the compound holding the lugs in place.
I'm not sure what the compound is. Maybe epoxy resin. but when you heat it up too much it feels like sealing wax.
Yes i'm that old I remember dad using sealing wax on documents.
It does depend on the wire being used, some of the wires i have seem to take a lot of heating, especially the military grade.
IMO military grade wire is probably overkill in an effect, especially the teflon insulation stuff.
Save it for a rocket launcher.

Quote from: Kipper4 on April 30, 2016, 05:08:37 PM
What what what?
Its working. Excellant.
Myself and many others use the tonepad offboard wiring no 5.  http://www.tonepad.com/getFileInfo.asp?id=76
Be sure to note the direction of the lugs on the switch bottom.
I now wish I had one of those gif images to share that show how these switches work. Anyone.

I've effed up some switches in the past by too much heat, that warms the compound holding the lugs in place...

It's certainly possible that I melted some of the goo that surrounds the switch lugs and I guess that could have done bad things.

Re: The offboard wiring, I couldn't link from the tonepad page to see exactly what you are talking about. Were you referring to a PCB that hooks up to 3PDT switch so you can wire the switch easier? I have some of those, but I'm concerned that if the switch is busted that still won't work?

Is there an obvious test I can do to see if the switch is defective or if the wiring is incorrect?

Out of circuit, connect your meter to the center lug of each throw, then check each position that the switch closes and opens as it should. Also check the top and bottom to make sure they're not shorted at all, and each throw to each other throw. There could always be some gobbledeygook going on inside. I also use alligator clip leads to temporarily connect to the wires from the pcb to make sure it checks out before final soldering.

Glad to see it's coming together!

You can test the switch to see if it's still functional with the meter on beep (connectivity)
In this thread reply 184 page 10 Marc (Bluebunny) explains how it works
Use the meter to confirm all is well.

http://www.diystompboxes.com/smfforum/index.php?topic=970.180


And in this thread reply 24 shows the tonepad off board wiring I have used for sometime.

http://www.diystompboxes.com/smfforum/index.php?topic=75778.20


I'm not as keen on the ggg documents. It hurts my eyes.

OK, I think I am now getting how these switches work!  :icon_idea:

So I've seen a few pages and kits that have different suggestions for 3PDT wiring. Is it the case that different pedals require a different bypass wiring scheme, or that any garden variety pedal can use the same wiring scheme, but there are multiple ways to do it?

In other words, let's say the instructions tell me one way to wire it. Can I use the tonepad method instead?

Quote from: Kipper4 on April 30, 2016, 06:29:34 PM
You can test the switch to see if it's still functional with the meter on beep (connectivity)

Might want to go beyond continuity and measure actual resistance.  Like if you get 25 ohms, for instance, it will beep, but that's not a good connection for a switch.  You want a fraction of an ohm, if not dead zero.  Just sayin'.

Quote from: cnspedalbuilder on May 01, 2016, 02:10:51 AM
OK, I think I am now getting how these switches work!  :icon_idea:

So I've seen a few pages and kits that have different suggestions for 3PDT wiring. Is it the case that different pedals require a different bypass wiring scheme, or that any garden variety pedal can use the same wiring scheme, but there are multiple ways to do it?



In other words, let's say the instructions tell me one way to wire it. Can I use the tonepad method instead?

Yes and yes for true bypass switching.

So for newbies, here is a site that did a nice job of explaining what the 3PDT does:
http://www.coda-effects.com/2015/03/3pdt-and-true-bypass-wiring.html

Rob, when you said test out of circuit, did you mean that I should disconnect all lines linking the PCB with the footswitch? Right now, footswitch is wired up, but disconnected from in and out jacks.

I started testing and the switch will toggle between the top and bottom rows. Anyway when i run continuity from Lug 2 it alternates between Lug 1 and Lug 3 depending on switch position, so that seems normal. Likewise, lug 5 will switch connections between Lug 4 and Lug 6.  Lug 8 will show continuity with Lug 7 in one switch position. When switch is reversed, Lug 8 shows continuity with both Lug 7 and Lug 9.

I don't know if Lug 8 continuity should look like because there is a jumper connecting the bottom row input jack line (lug 3) to the upper right lug (lug 7), which makes this all a bit counter-intuitive. as Rich put it, the wiring is headache inducing.

Thoughts? Other tests?

If you guys think that the switch is fine and its something weird in the wiring, then I am inclined to disconnect all the lugs and re-wire with a 3PDT PCB, so that I can get everything in its right place.

p.s. Therm, I was having a little trouble with DMM resistance check. Will have some coffee and come back to it. :)

QuoteLug 8 will show continuity with Lug 7 in one switch position. When switch is reversed, Lug 8 shows continuity with both Lug 7 and Lug 9.

this. suggests too much soldering heat on the lugs, and one has shifted, under pressure of the internal springing contraption. you can use the other two poles as normal, but not in anything mission critical.

good work on the trackdown.

Quote from: duck_arse on May 01, 2016, 11:19:36 AM

QuoteLug 8 will show continuity with Lug 7 in one switch position. When switch is reversed, Lug 8 shows continuity with both Lug 7 and Lug 9.

this. suggests too much soldering heat on the lugs, and one has shifted, under pressure of the internal springing contraption. you can use the other two poles as normal, but not in anything mission critical.

good work on the trackdown.

Stephen, are you saying I found the problem?????!!!!!!?????   :icon_eek:
does this mean that if I replace the 3PDT, it should be fine?

I think I need all of the lugs, in order to hook up to LED, PCB circuit in, and PCB circuit out, right?

Even the thought of snuffing out the bug makes me excited.

So based on the feedback so far, I went ahead and ordered a few extra 3PDTs and figured I would replace the one that has the continuity problem.

Is there anything else I should test at this point?

"Is there anything else I should test at this point? "

Only your sanity after wanting to make your own.........

Seriously congratulations at least now you have a working pedal.
You got through a debug.
Just go easy on the switch soldering next time. It's one of the most expensive componants in most of my builds.
I use leaded rosin core solder because it has a lower melting point as do most here I believe.
Just as a point of intrest.

If you prepared to forego the led indicator in a build you could still use the switch as Duck Arse pointed out thus.

"you can use the other two poles as normal, but not in anything mission critical."

Good news! I installed new switch and can toggle pedal on and off. This means that the switch was definitely the problem.

Slightly bad news--the LED now either wants to stay on or off. So when I wired the new switch, I ran it through a 3PDT board that I got from GuitarPCB.com (along with some nice hookup wire). Here's the URL: http://www.guitarpcb.com/apps/webstore/products/show/3436229

The thing is, the GGG schematic basically shows the LED + going to the "L" pad in PCB, and the - lead connects to switch (looks like the side of the switch that activates pedal by routing input/output through PCB). I have tried to replicate this with the 3PDT board, but no luck.

I tried running the - LED lead to a ground pad on the 3PDT board, and + LED lead to "L" pad on PCB. With that, light always stays on.
I have tried running the -ve LED lead to the middle "D1" pad of the 3PDTboard and the +ve lead to the right-side (white square) D1 pad. With that, light always stays off. Either way, pedal works fine, but I have to fix this last bit.

So I realize I'm probably lame for even using this 3PDT board, but I really wanted to have clean wiring and minimize heat damage to the new switch. I'm sure there is a simple fix, but I can't think of it right now probably because I am not sure how board relays power to LED. Do you have any suggestions for rewiring?

BTW, thanks you guys for all the time and effort you have put in to help!

I always like to say "draw the circuit". so, draw the circuit. draw the switch poles correctly, so all the N/O face one way, and the N/C, well, you can work out which way they will face. then you will see what needs to be connected to what else, and more importantly, when they will actually be connected.

then it's a matter of working out how your board wiring wires the switch poles (never used one of the boards, can't help you with them) compared to your circuit drawing. then, the shingles will fall from your eyes, and the light will be dazzling.

in which case, increase the CLR.

or email/call GGG
even from a close up look at the switch pcb i'm having trouble with it.

You could test the water with a spare led and try touching the legs to the D1 trio of holes and throw the switch. worst case scenario you blow an led and see the magic smoke at your own risk.

Stephen and Rich, this is super helpful. Can I ask a couple of followups?

1.

Quote from: duck_arse on May 04, 2016, 10:37:12 AM
draw the switch poles correctly, so all the N/O face one way, and the N/C, well, you can work out which way they will face.

->Sorry novice question, but what does N/O and N/C mean?

2. Forgetting my problem for a moment, how is power routed to LED normally? For instance, in the GGG circuit, it shows one end of LED going to "L" pad on PCB, and the other going to a switch lug. I wasn't exactly clear how that wiring toggles the LED on/off. is the -vs lead on the LED supposed to go to a ground point or to another part of the circuit?

Thanks!

This might help explain it a bit more. Lets hope its not more confusing

http://www.stewmac.com/How-To/Online_Resources/Learn_About_Guitar_Pickups_and_Electronics_and_Wiring/3PDT_Stomp_Switch_Instructions.html

N/O  normally open
N/C  normally closed

the throw that the led is used for, Illuminates the led when the pcb is in circuit (Not Bypassed)
So When the input jack tip is connected to the pcb input
and simultaniously the output jack tip is connected to the pcb out

the led throw connects the led cathode (minus pin) to ground and allows currant and voltage through the led therefore lighting it up.


the led anode (Positive pin) goes to a CLR (current limmiting resistor) and the other end of the clr goes to V+ (9V).
Why use a clr? Because it dulls the led brightness otherwise it will burn your retina and it prolongs the leds life some suggest.

Hence this from DA

"then, the shingles will fall from your eyes, and the light will be dazzling.

in which case, increase the CLR."

I had understood the bit about the switch, but didn't know about how the switch toggles the LED, so thanks for sheddling light  ::) on this issue!
BTW, you guys are great. I have learned a ton of information from your posts.  ;D
Will keep you posted on what happens next!
p.s. I tried testing a spare LED and with one of the tests, got a flash of light and then no response, so maybe I saw the magic  :icon_redface:

IT IS DONE!!!!!!!!!!!!!!!!!!!!!!
:icon_lol: :icon_lol: :icon_lol: :icon_lol: :icon_lol:

In case anyone reads this in the future, here is the summary of the thread: I built a Phase 45 pedal that generated horribly loud feedback when turned on. After going through a PDT switch, two LEDs, and rewiring and resoldering almost every connection, we solved the problem. The 3PDT switch was broken, creating a short that probably fed output back into the circuit, causing feedback. Also, FYI, when wiring a standard LED to a GPCB 3PDT board, it's necessary to run the ends of the LED into the two D1 pads that are not white. A 2K resistor should also be added to the CLR pads. The "L" pad on the PCB does not need to be used.

This is probably a fantastic thread for novices to learn how to troubleshoot or just to restore faith in humanity.
Everyone who posted on this thread has been seriously amazing. With your patience, I learned how to:
-Test voltages with a DMM
-Build an audio probe
-Test an IC, capacitor, and a 3PDT switch
-Wire a 3PDT, along with the underlying mechanics of how it works
-Enjoy the support and creativity of a community of experts

Thank you guys, seriously!

(spotted an error on the layout I posted at page 4, one line break more then needed- bridged with leftover wire and corrected layout)

(http://www.olaolaonline.net/thumbs/20160519232035_mxr_phase_45_0001_tn.png) (http://www.olaolaonline.net/page.php?image=20160519232035_mxr_phase_45_0001.png)

It finally works as supposed. take this layout as verified