OK people, Christmas is here! :icon_cool:
Here is the board tracings. There are 2 boards (upper/lower), connected by 7 bridge pins, so numbered on the drawings. So, pin 1 to pin 1, and so on.
The lower board is double sided, so blue trace lines are one side, red the other. The pale highlighting is the components.
There are 3 unknown trannies on the lower board, the writing has been sanded off, but they're silicon. They'll need to be diciphered by the experts here.
Some resistor values were very hard to decipher, because the resistors are so tiny, so I read the colors both ways, and highlighted my thoughts.
There are 2 trimmers on the upper board, 25K and 100K.
The transformer, only the primary side is used. I wrote the resistances I read on the poles on the drawing.
Without further ado;
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/Geminiupper001.jpg)
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/Geminilower001.jpg)
It was real delicate work, like eye surgery, but I think it should be correct. I'm 90% sure about the traces to the 5n6 cap (next to pin 1) on the lower board. It was near impossible to see under the dual pot, but I don't think there is any other traces going to this cap.
I know it may seem that the right side of the images here are cut off, but if you download it to your computer, it will appear.
It would be nice if someone could now draw up a proper schematic. From that, I can do a vero layout.
Let the dissection begin!!
Alright, I had a slow shift at work :icon_mrgreen:
There are 3 transistors that had the facing erased, to hide they're identity, but with some research I think 2 of them are for the Millenium bypass. I labeled them as such.
The third one (marked ???) is troubling me though. Again, my internet diving is pointing me towards a type of jfet buffer, but I can't be certain. Personally, I would put my money on the jfet buffer, though I couldn't say which jfet would be the right one. A BS170, or 2N7000 might be fine here, but I would appreciate an expert opinion on that.
As for the transformer, I'm getting resistances of 216 ohms on the secondary, and 463 ohms on the primary, so I've indicated the Xicon transformer that comes closest (200/500).
Here's my work to date;
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/Geminischematic.jpg)
So, what's the verdict on that last tranny? R.G.? Paul? Mark? Anyone?
I'm going to record voltages next. :icon_cool:
*EDIT* - I corrected 3 resistor values on the schematic. The 301K is actually 308K, and the two 25.5K's are both 36.5K's. These corrections ARE NOT reflected in the hand drawn trace. You've been warned.
Please forgive me but what's this all about?
Edit: I just did a search and you appear to be reverse engineering a pedal.
I just felt like I walked in the middle of a conversation. Please carry on!
This the (unverified) schematic of the Spaceman Effects Gemini III Dual Fuzz Generator. It's a sweet parallel fuzz, germanium on one side, silicon on the other, and you can blend the two together. Some videos on Youtube.
They're as rare as the Pope's sh*t, since there's only about 160 or so in existance.
Quote from: Bill Mountain on May 17, 2012, 03:18:48 PM
Please forgive me but what's this all about?
Edit: I just did a search and you appear to be reverse engineering a pedal.
I just felt like I walked in the middle of a conversation. Please carry on!
:icon_lol:
No worries Bill. It's all good in the hood.
Looks cool, never heard of it before, I'll have to check out youtube for videos.
The last transistor could be virtually any NPN transistor, it's a booster, presumably to make up for volume lost in the tone controls and mixer before it.
Quote from: slacker on May 17, 2012, 03:48:27 PM
Looks cool, never heard of it before, I'll have to check out youtube for videos.
The last transistor could be virtually any NPN transistor, it's a booster, presumably to make up for volume lost in the tone controls and mixer before it.
Wouldn't it be a buffer?
Edit: Nevermind. I was looking at it upside down!
Quote from: slacker on May 17, 2012, 03:48:27 PM
Looks cool, never heard of it before, I'll have to check out youtube for videos.
The last transistor could be virtually any NPN transistor, it's a booster, presumably to make up for volume lost in the tone controls and mixer before it.
Hmmm, I thought that as well, but what's throwing me off is the fact that they ground the info off the tranny. Actually, they did the same with the fet and tranny for the millenium bypass, but tracing the circuit, it became obvious to me what they were.
Problem is that I don't have enough smarts yet to negotiate weather it could be a jfet or transistor yet. With the info I do have, I'm scouring the net looking at similar circuits. One I did find, I thought fit the bill;
(http://www.daycounter.com/Calculators/JFET-Bias/JFET-Buffer.gif)
But, it's not quite right. Looking at the layout again, I'm backtracking to the transistor again. Especially looking at this;
(http://www.beavisaudio.com/techpages/Buffers/Buffer_TSTransistor.gif)
What's really throwing me off too, is the lack of a resistor opposite the 4M7 to bias/voltage divide. I think I might have to just construct this part of the circuit on the breadboard, and see what I get. Like I said, I don't have enough smarts to decipher this circuit just by looking at the lines and numbers. :icon_sad:
I think you're getting confused because of how you've drawn it. Try standing on your head :) and it will make more sense.
Quote from: slacker on May 18, 2012, 06:45:45 AM
I think you're getting confused because of how you've drawn it. Try standing on your head :) and it will make more sense.
:icon_lol: +1.
How about this?
(http://www.learnabout-electronics.org/images/image3112a.gif)
Which gives me this;
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/Outputamp.jpg)
I guess I'll have to breadboard this to find out which transistor gives the best results. Considering the fact that they ground the facing off the transistor and jfet to hide their identity on the Millenium II bypass circuit, it wouldn't suprise me if it's some mundane transistor like a 2N3904, or something like that. It's funny that they went to the trouble of grinding the numbers off this on as well, but I guess in my case, it seems to be giving me a good fit. :icon_lol:
BTW, I came across a great little demo on simple transistor biasing, and what it does. The guys voice is a bit monotone, but IMO his demo is excellent. Really good for a "visual" creature such as myself. :icon_lol:
Alright, I breadboarded that circuit with a 2N3904, and it works. I didn't have any 4.7M's, so I used two 2.2M's in series to get close.
I've come to the conclusion that the unknown transistor is probably any low power small signal tranny (2N3904, 2N2222, etc.), used as a final booster. Especially since this pedal can be very loud at full tilt. Right now I'm at unity with the volume at about the 9 o'clock position.
I'm going to update the drawing, and leave this open for anyone to try different trannies to taste.
*EDIT* - Drawing is updated. Just takes some time to make it's way through Photobuckets servers sometimes.
Yeah, that's it. Like you said pretty much any NPN transistor will work in there.
Thanks for your input Ian. Much appreciated.
BTW, I'm triple checking the schematic vis a vis the layout, and I spotted a couple of errors. They're now corrected, the schematic should update shortly.
On the transformer, I'm willing to bet any 10k Pri. transformer would work. The Xicons usually have the number stamped on the frame, don't they? I was looking at the 42TU012, which is 10k:5k, and 425R:220R. The 42TM019 that Steve sells should work fine. It looks to me like it's just a pickup sim, but I'm not sure if it's going to play differently given that it's a higher DC resistance, i.e. smaller dia. wire. I'd say the 42TL019 would be the best. Still a 10k primary (assuming the primary is 10k), but the DC is 450R, much closer to the target reading of 465.
Quote from: Earthscum on May 18, 2012, 05:28:56 PM
On the transformer, I'm willing to bet any 10k Pri. transformer would work. The Xicons usually have the number stamped on the frame, don't they? I was looking at the 42TU012, which is 10k:5k, and 425R:220R. The 42TM019 that Steve sells should work fine. It looks to me like it's just a pickup sim, but I'm not sure if it's going to play differently given that it's a higher DC resistance, i.e. smaller dia. wire. I'd say the 42TL019 would be the best. Still a 10k primary (assuming the primary is 10k), but the DC is 450R, much closer to the target reading of 465.
Yeah David, you're right. As long as it's 10K, and as close to the primary 463 ohms, you should be in business. I think that there is quite a high tolerance in this little transformers anyways. Besides, at 2 dollars a piece, I would maybe buy 2 or 3 different ones, and test to see if there is any difference.
For the sake of clarity, I've done a redraw.
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/Geminischematic_new.jpg)
It's a bit easier to follow now. I did forget to update the transformer part number though (sorry David :icon_mrgreen:). I'll fix that later today.
Wow!! Thanks for the post and all your effort!!
Gotta build this one!
How did you get your hands on one of these? Gutshots?
Tony
Quote from: dorrisant on May 23, 2012, 11:47:20 AM
Wow!! Thanks for the post and all your effort!!
Gotta build this one!
How did you get your hands on one of these? Gutshots?
Tony
No prob. I did manage to get my hands on one. It's a great sounding pedal.
Heads up though!!! Some errors were brought to my attention, and after further inspection, digging, etc., I've made some changes to the schematic. Notably, one tranny is an AC176, and NOT an AC128. Huge difference, I know, but it was an assumption on my part since the writing on the can was on the underside. A PM by another DIY'er made me go back and really take a good look. I managed to spot that in the reflection of the tranny in the tinned ground plane. Two cap values have been corrected, misread on my part. A resistor value corrected, that was a copy/paste typo. The transformer part number has been updated as well to match to a closer model.
Here's the new drawing;
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/Geminischematic_new.jpg)
That should be it. When I get some time, I'll whip up a vero, unless someone feels like beating me to it, be my guest.
Alrighty then...
Took me some time, I've been rather busy of late, but I managed to get all the voltages from the trannies. They follow the numbering of the latest schematic, so without further ado;
POWER SUPPLY VOLTAGE = 9.15vdc, NO LOAD ON CIRCUIT, BOTH GAIN SWITCHES SET TO MINIMUM (POSITION 1).
Q1-
E=2.017v
B=1.882v
C=1.491v
Q2-
E=1.522v
B=0.946v
C=0.769v
Q3-
E=1.547v
B=1.586v
C=1.672v
Q4-
E=1.271v
B=1.863v
C=3.164v
Q5-
E=1.752v
B=2.182v
C=2.207v
Q6-
E=1.184v
B=1.752v
C=2.207v
Q7-
E=161.8mV
B=0.694v
C=1.507v
Just thought about this... on the "mystery" Q7, can you get a diode reading? It almost seems, by the voltages, that it's PNP. Maybe you can get lucky and it will give up it's identity on-board.
eta: looking at it, if it were a PNP, I don't think it would be working... it would be biased off.
Quote from: Earthscum on May 27, 2012, 07:57:08 PM
Just thought about this... on the "mystery" Q7, can you get a diode reading? It almost seems, by the voltages, that it's PNP. Maybe you can get lucky and it will give up it's identity on-board.
eta: looking at it, if it were a PNP, I don't think it would be working... it would be biased off.
I figured that the voltages would go a long way for someone more gifted than myself to maybe nail this one down. Like I mentioned before, the face has been ground down thus erasing the identity. Maybe an NPN, but an ECB pinout? I was also wondering if this could be a jfet, but I didn't want to risk taking it out to analyse with the Peak. Just separating the boards for the tracing was a major undertaking. In any case, I put this portion of the circuit on the breadboard using a 2N3904, and it worked fine.
It's too bad that my bench is loaded right now, or else the breadboard would be running this right now. I'd like to build this, but using Russian trannies, I've been stocking up on them. Maybe call the clone the "Soyuz Dual Fuzz", rekindle the great fuzz... err... space race. :icon_lol:
Then I'll have to send it down to my bro Jimi for the video shoot, of course. :icon_mrgreen:
I was just going through Mouser looking at SMD Jfets and it dawned on me that this MIGHT be a P-Channel Jfet, but I'm not exactly sure on how they function, or would function in this instance. Just a thought... it's the ground face that's throwing me, lol. It's either something special, or something mundane, but either way I want to know if the cat lived or died, dammit! :icon_lol:
Maybe it is a BC183? It is NPN with a ECB pinout.
If you look at his original drawing, it is like a NPN (EBC) that is backwards (and could be). The pinout, if NPN, would actually be CBE. The voltages reflect this, the base is 1 diode drop above the "collector" (should be NPN=Emitter). It would either be a CBE pinout, DGS Japanese fet (but gate would be pulled low rather than high) or PNP (but again, the base is wired backwards). UJT or something?
What might be throwing you guys off, is the fact that I used a transistor symbol in the schematic. Like I mentioned before, looking at the flat side, I'm "assuming" that it's a transistor with an EBC pinout.
The voltages that I've provided for this "transistor" are also take from left to right, "assuming" that they are the EBC voltages.
I just wanted to clear that up, before anyone trips on their shoe laces. When I get some time, I'll breadboard a fet in here, and see what happens. Personally, it wouldn't surprise me if it's something banal like a 2N3904, or something similar, here. After all, they even took the time to grind the numbers off the tranny and fet for the Millenium bypass, like we wouldn't figure out what THAT was. I think maybe this is a similar "red herring". Besides, look at Q4 (and Q1 for that matter), they all share the same emitter resistor value. I love a conspiracy theory, just as much as the next guy, but I'm leaning toward BJT here.
Thanks for taking the time to brainstorm this guys.
Actually what is throwing me off is the reversed pinout.
If you guys think the last schematic is verified, I would be willing to try to come up with a pcb trace...
Tony
Quote from: dorrisant on June 07, 2012, 12:56:26 AM
If you guys think the last schematic is verified, I would be willing to try to come up with a pcb trace...
Tony
Hi Tony,
The schematic, insofar as where the lines are going, is fine. The only thing up in the air right now is Q7, but that wouldn't affect a PCB trace at all. Although, a single sided PCB of the entire circuit will require a larger enclosure than the original. No biggie, for me, heck, I planning on doing this on vero :icon_mrgreen:.
If you really want stay true to the original, you can even use my hand drawn versions, at the beginning of the thread. These are taken directly from a unit. The upper board is single sided, but the lower board is double sided. The component side traces on the lower board are highlighted in red. The pots are mounted directly to the PCB, as well as the miniature toggle switches. Along with the components, you might have enough dimensions to scale the sketches properly. The connection points on the edge of the boards labelled 1 thru 7, should also line up between the two board when they are laid one over the other. There is solid core wire used here as connectors / stand-offs. Both boards use a ground plane to ground whatever components need it. Looks great in the original, and saves on tracing as well.
Cheers,
Dino
If you have any gutshots, you could post them or pm me... if you don't have any, just let me know and I will proceed anyway.
Tony
Quote from: dorrisant on June 07, 2012, 03:50:59 PM
If you have any gutshots, you could post them or pm me... if you don't have any, just let me know and I will proceed anyway.
Tony
I took a trace side shot of the top board, but for some unknown reason, I neglected to take a trace side shot of the lower board :icon_rolleyes:.
I`ll post the top board pic later.
Watching with interest. Nothing to really add, but:
Quote from: Earthscum on May 28, 2012, 02:48:37 AM
...but either way I want to know if the cat lived or died, dammit! :icon_lol:
Of course it did! ;)
OK, here are the pics. I suddenly remembered why I didn't bother with trace side shots of the lower board. It's because the pots and switches are mounted on the board directly, and I was not prepared to desolder everything for that. I do have component side shots though. Like I said, you can use the sketches to run the traces as well.
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/DSCF0978.jpg)
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/DSCF0977.jpg)
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/DSCF0976.jpg)
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/DSCF0975.jpg)
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/DSCF0974.jpg)
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/DSCF0972.jpg)
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/DSCF0981.jpg)
Hope that helps you out.
Cheers,
Dino
I'll just subscribe to the thread :D
Good work.
Carry on as you were.
Oh yeah! That will help... Great pics!
Gonna see what I can do with it this weekend.
Tony
Quote from: dorrisant on June 08, 2012, 10:03:57 AM
Oh yeah! That will help... Great pics!
Gonna see what I can do with it this weekend.
Tony
Cool. Let me know if you need any more info. I`ll try tp help any way I can. I really want to clone this sucker, it`s a great sounding fuzz. If you make some boards, I`ll buy a set or two from you.
Cheers,
Dino
Hey guys, check this for errors if you don't mind. Don't beat me up too bad if things look too tight... I usually just cram it all in and then spread it out to be a little less crowded. I tried to get away with as few jumpers as possible... it is single sided though, so it is what it is. Let me know if I've screwed anything up. I did not double check it before calling it a night and I just wanted to post it and get the ball rolling. So here you go...
(http://i946.photobucket.com/albums/ad304/dorrisant/photobucket-22606-1339460430116.jpg)
(http://i946.photobucket.com/albums/ad304/dorrisant/photobucket-31118-1339460446181.jpg)
Tony
Nice Tony, real nice.
I'll go over it tomorrow. Just one thing, might be a good idea to mark the transistor pins (e,c,b) on the layout, just for the sake of clarity.
I'll let you know what I come up with. Actually, it will also help me with a vero layout as well.
Cheers,
Dino
I was gonna mark those trannies but ran out of energy and time. I will mark them later. I also want to re-route the ground trace on the bottom right corner... just to make the board a tiny bit smaller if needed.
I'm glad you might find it useful. Looking forward to your comments and suggestions.
Tony
Carry on Gentlemen, would love a PCB layout for this. I think my feeble brain would take years in delivering a good layout for
the peeps. Lately, I have been designing my own layouts for boards and using other free ones here and on the webs. Sometimes
I'll get some boards from musicpcb or bean. I like when someone make a new diy transfer. Makes me feel in intune. A board for this
and the Wem Project 5 would make for some great summer fuzzies.....
Quote from: digi2t on May 27, 2012, 07:47:09 PM
Q7- (Mystery transistor, not sure of pinout. I'm going from left to right, looking at the flat side of the tranny. Need verification here.)
E=1.430v
B=0.694v
C=161.8mV
I simmed the Q7 circuit, using a variety of common NPNs, and get the following voltages
C = varies with device between approx 1.3 and 2 volts, higher gains give lower voltage.
B = approx 0.7 - 0.8 volts
E = approx 150 -160 mV
So basically what you've measured if you reverse E and C. I'd just go with Keen's law (http://www.geofex.com/effxfaq/keenslaws.htm) with this tranny.
Quote from: slacker on June 12, 2012, 01:59:00 PM
Quote from: digi2t on May 27, 2012, 07:47:09 PM
Q7- (Mystery transistor, not sure of pinout. I'm going from left to right, looking at the flat side of the tranny. Need verification here.)
E=1.430v
B=0.694v
C=161.8mV
I simmed the Q7 circuit, using a variety of common NPNs, and get the following voltages
C = varies with device between approx 1.3 and 2 volts, higher gains give lower voltage.
B = approx 0.7 - 0.8 volts
E = approx 150 -160 mV
So basically what you've measured if you reverse E and C. I'd just go with Keen's law (http://www.geofex.com/effxfaq/keenslaws.htm) with this tranny.
Ian.... I love you man!!!! :icon_lol:
So, that means that I just have to flip the Q7 symbol on my schematic, right? It`s just a bit bizzarre for me, I`ve crossed paths with a tranny yet that has the E on the right, and C on the left, when you`re looking at the flat side with the legs down. To me, it`s always been the other way around. Maybe that`s what was throwing me off. Also probably why they sanded the numbers off this sucker, they didn`t want to give the baby away.
Ian, you`re a true scholar and gentleman. Thanks dude! Now I have to do some research and find out which tranny fits this bill, backwards pinout and such.
On another note, I scored a bag of 75 AC128`s and 75 AC176`s last week. So far the Atlas tester is giving me pretty good numbers on a majority of them. So, it`s going to be a toss up between them, or Russian trannies.
Cheers,
Dino
Yet another reason I didn't label those suckers before... just kidding!
Do feel free to label them and repost the trace if you can...
Tony
No problem Dino, happy to help figuring this beast out.
If your voltages are like this
(http://www.eskimo.plus.com/fxstuff/Geminisnippet.jpg)
then your schematic is fine, no need to flip anything. If the 1.4V and 160mV are switched then it's back to the drawing board on what the transistor is.
A lot of European transistors have the pinout you described, have a look at the datasheet for a BC547 or BC550 for example, they're high gain general purpose trannys, basically equivalent to your 2N5088/2N5089.
Quote from: slacker on June 12, 2012, 04:22:01 PM
then your schematic is fine, no need to flip anything. If the 1.4V and 160mV are switched then it's back to the drawing board on what the transistor is.
A lot of European transistors have the pinout you described, have a look at the datasheet for a BC547 or BC550 for example, they're high gain general purpose trannys, basically equivalent to your 2N5088/2N5089.
Drive them hard, and BC's have a nice tone (to my ears). I used a BC108 (or 109?) in my Muff because of the way it spiced up the sound (into SS, anyways... can't vouch for tube). I've really only noticed the most tonal difference when they are getting pounded pretty good, though. I've kind of made a habit of putting MPSA13's in the front of my circuits and BC's at the end (or where they get driven the hardest with the least post-filtering). Just an idea, might be "flavoring" this circuit.
Quote from: slacker on June 12, 2012, 04:22:01 PM
No problem Dino, happy to help figuring this beast out.
If your voltages are like this
(http://www.eskimo.plus.com/fxstuff/Geminisnippet.jpg)
then your schematic is fine, no need to flip anything. If the 1.4V and 160mV are switched then it's back to the drawing board on what the transistor is.
A lot of European transistors have the pinout you described, have a look at the datasheet for a BC547 or BC550 for example, they're high gain general purpose trannys, basically equivalent to your 2N5088/2N5089.
Yup, that's it. It's a normal EBC configuration, like a 5088, etc. I think the fact that I measured from the backside before must have screwed me up (mirror image deal :icon_redface:). I think we've got that problem licked. This time I snuck a probe under the top board to the legs on the component side to take the voltages. That way I'm sure of the orientation. It's not a BCxxx or 2N2222A can package, just a normal silicon package. Does your sim allow to see what gain range gets us into the voltage range we have here?
Another thing I was thinking about, is ditching the hi/med/lo gain switches for pots. I'm going to have to sit down and figure out the parallel resistor values, and see if I can fake them with a pot. That would be great, allowing us to more precisely adjust the gain of either side.
@David - Right on the BC108/9 deal. I run everything into SS, and they do sound pretty good in my rig as well. Could be worth while trying these in here.
Geeeez.... I can't wait to get my other projects cleared off the bench, so I can start working on this this. :icon_rolleyes:
@dorrisant - I looked over the PCB layout, but I found that there is a .22uF cap missing before the transformer. Might want to have a look at that. Also, I think it's going to be a tough board to work with, I'm not sure that the transformer will fit onto the board. Maybe have a look at the dimension specs of the transformer. There is no connection point on the board for the P1 trimmer to connect to (going to ground). That's all I had time to look at today.
Thanks for your work guys. I'm sure we're going to lick this sucker.
Just had an update from someone on the other forum who's breadboarding this right now.
There is an error on one of the resistor values. The resistor between B and C on Q3 is NOT 15K. It is 150K.
His wife actually confirmed the color code from the pics I posted. He said that it went from an overdrive, to a great fuzz when he swapped out the resistor. I went back into it, and this time I lifted the resistor to test, and sure enough, it reads 150K. The 220K on Q2 is good. I had to test these two, because the colors are just so hard to read on these 1/8 watters.
I've updated the schematic, and the correct value should appear shortly.
Sorry guys. :icon_redface: Guess an appointment with the opthamologist is in order. :icon_lol:
Quote from: digi2t on June 13, 2012, 12:03:05 AMSorry guys. :icon_redface: Guess an appointment with the opthamologist is in order. :icon_lol:
No problem, man... have another homebrew... uh... you probably know what I mean.
Good call for the mystery contributer for the good eye! Please pass along the gratitude!
I love the video you posted... I heard some mean sounds there that I want to try out...
My layout remains unaffected by the resistor change... until you guys tell me what I f@#$ed up.
...And look at how many people have viewed/are watching this thread! This is so worth finishing. We are almost there!
Tony
Quote from: digi2t on June 12, 2012, 10:36:17 PM
Does your sim allow to see what gain range gets us into the voltage range we have here?
Sim said a 2N5088 was in the right ballpark. I whacked the circuit snippet on the breadboard and tried it with a few 2N5088 in the 400-500 Hfe range and the voltages were spot on to what you measured and what the sim predicted. Looks like we have a winner :)
Quote from: slacker on June 13, 2012, 03:13:08 PM
Quote from: digi2t on June 12, 2012, 10:36:17 PM
Does your sim allow to see what gain range gets us into the voltage range we have here?
Sim said a 2N5088 was in the right ballpark. I whacked the circuit snippet on the breadboard and tried it with a few 2N5088 in the 400-500 Hfe range and the voltages were spot on to what you measured and what the sim predicted. Looks like we have a winner :)
Excellent news Ian. Thanks a bunch... again!! :icon_smile:
I`ll add the info to the schematic. I`ll advise buddy who`s breadboarding it as to your findings as well. He`s waiting an a 2N3700 right now, but with a close sub, he says the circuit sounds really good.
Cheers,
Dino
More news on the Q7 front.
One of our fellow DIY`ers who is testing has reported that the following transistors will work here (with a description of the tone).;
BC239C - agressive, but smooth
BC550C - cleaner tone
2N5088 - more agressive than the BC550, but clean
All three, in the 400 to 500 hfe range, give close to, or exactly the same, voltage readings. Testing any one of these after the circuit is build should seal the deal as to the tone prefered.
Also, it was found that the 2N2222A`s tend to match the voltages best, are at, or close to, 100 hfe.
Another note; The 18.5K and 308K resistors may be sub`d with 18K and 308K. Much easier to find, and shouldn`t make any noticable difference tone wise. If you`re real picky, buy a batch and sift through them, I`m pretty sure that you`ll get the occassional one that comes close.
Cheers,
Dino
Just to clarify... the pcb is not made to mount to the transformer. I was gonna remote mount it and wire it from there... just two wires...
I will add the cap and repost... good eyes! Anything else?
Tony
Quote from: digi2t on June 15, 2012, 12:09:49 PM
More news on the Q7 front.
...
BC239C - agressive, but smooth
B550C - cleaner tone
2N5088 - more agressive than the BC550, but clean
...
Cheers,
Dino
?
why?
:icon_question:
Quote from: puretube on June 15, 2012, 01:17:40 PM
Quote from: digi2t on June 15, 2012, 12:09:49 PM
More news on the Q7 front.
...
BC239C - agressive, but smooth
BC550C - cleaner tone
2N5088 - more agressive than the BC550, but clean
...
Cheers,
Dino
?
why?
:icon_question:
Why?... Because it is there :icon_mrgreen:.
I must confess, I`m not aware of what he`s using for guitar and amp combo. I`m just repeating his findings for the sake of anyone else that might be working on this. Personally, I`m swamped in other projects right now, but in my opinion, the more info, the better.
@ dorrisant - I kind of figured as much on the the xformer. I`ll have another look at the layout over the weekend, and see if any other gremlins pop out at me. Thanks dude.
Well... first and foremost.... I wish to thank, from the bottom of my soul, chaospere for all his hard work. His wife too, long story, but she deserves it as well. He's build the clone, and reports that it sounds amazing. A real keeper. Not only that, but he's put together a wonder build .pdf, including a PCB transfer, parts list, wiring guide, and hell... why not, tranny voltages.
I'm so happy, I could almost cry.... OK, get a grip Dino...
The build paper is here; http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=47579&g2_GALLERYSID=ace1fcc31b7d711f6135f011d3090860 (http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=47579&g2_GALLERYSID=ace1fcc31b7d711f6135f011d3090860)
To cut down on parts, and make the PCB a bit smaller, the Millenium bypass has been omitted, and the wiring is done in true bypass fashion. He also added a 1N400x protection diode, since we both agreed that original's use of a 1N4148 diode for protection was a bit weak.
There are only 215 of these pedals ever made, and word has it that the last batch of 50 made, were the last ever. I was freakin' lucky to get my hands on one, and now everyone can enjoy this beauty.
I'll eventually get down to doing a vero of this as well, for those of us that don't have the capacity to etch (your's truly included :icon_mrgreen:).
Cheers,
Dino
Nice project. Complete after just three pages. Way to go.
Props to Chaosphere (and his wife).
I'm making no promises about when, but next time I'm etching I'll let you know, for this or something else.
-Aston
Quote from: Skruffyhound on June 21, 2012, 05:33:05 PM
Nice project. Complete after just three pages. Way to go.
Props to Chaosphere (and his wife).
I'm making no promises about when, but next time I'm etching I'll let you know, for this or something else.
-Aston
Thanks Aston. I'd be happy to pay you to etch me a board, when you get the time. No rush. PM me if that's kosher with you.
Cheers,
Dino
Wow! Great job guys!... Gonna go etch...
Well, something new to add here... this just came up in another thread:
Quote from: CynicalMan on June 25, 2012, 09:03:43 PM
Not with a modern silicon transistor, the reverse beta is far too low. For most silicon transistors, the reverse beta is below 10, and it's often even below 1. You can read about the manufacturing differences here:
http://www.muzique.com/lab/reverse.htm
Howz about that?!? :icon_eek:
I love a good mystery. ;D
eta: Best highlight: "However, the most interesting effect is when this reverse booster circuit is driven into clipping - it clips in a matter totally unlike that of the basic common emitter circuit! The overdriven reverse booster generates a mess of harmonics different from other clipping circuits and configurations."
If that's the way this was designed, bravo to them! That's a really neat trick I'm gonna have to explore... I have a couple of old metal can Si's, too.
I don't think there are any reverse-bias transistors here, but there is a Harmonic Percolator-style stage, with the AC176 and one of the AC128s. It looks sort of like this:
(http://folkurban.com/Site/689_25279.gif)
I'd like to take a closer look into how that works. It's probably one of those old high-gain cookbook transistor circuits like the Fuzz Face or the Mini-Booster.
I should also point out that the voltages you have on Q7 do indicate an hFE of around 500.
First off, thank you Alex for the info above. I've been so wrapped up with the Ludwig clone of late, that I've just seen your post.
I had some time tonight, so here is a vero for us vero freaks out there;
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/GEMINIVERO.jpg)
It is unverified, but I've posted it so that maybe someone else can have a look and proof it. I'll be going over it as well over the next couple of days, but I think it should match up with the schematic. I also added the Millennium Bypass to it, as per the original. Chaosphere left it out, but it would be easy enough to leave out the extra parts to make it true bypass. I figured it's best to have it, and at least present the option. Chaosphere used my schematic to draw his (much cleaner!) schematic, so you can use his, or mine to verifiy the Mill. Bypass layout.
Please note as well, the two gain switches are dp3t center off, and not dpdt.
Cheers,
Dino
Went over it again today, and found a couple of errors. Missing cut in the Mill. Bypass circuit, and Ge. tone section was incorrect. Now corrected. Everything matches up to the schematic, so if you downloaded the earlier version, discard and use this one.
Cheers,
Dino
Ok, I think I understand the AC128/AC176 section.
(http://i.snag.gy/K5ORP.jpg)
The transistors produce a DC voltage over C18, but it drains most of the AC voltage to ground. So it mostly acts as a voltage source, at around 1.5V according to the build doc. That makes the two transistor stages act separately, like a PNP stage with a -1.5V supply followed by a NPN stage with a 7.5V supply.
But any AC signal that does get through will act as positive feedback. Since the capacitor has a higher impedance to bass, some of the bass isn't drained, so there's some positive feedback with the low frequencies. But also, the higher emitter impedance means that the transistors' gain is lowered for the bass. With these two effects combined, the capacitor boosts signals around 100Hz by 3dB compared to an ideal voltage source. I tried tweaking the values of C10, C11, and C18 in LTSpice, and I could get quite a bit of resonance.
I should also mention that the voltages for Q2 and Q3 look wrong in the build doc. Q3's emitter should be lower than its collector and Q2's collector should be lower than its emitter. Maybe the two got swapped?
I have been following this thread and must have read it 2 dozen times from start to finish. I have a lot of respect and admiration for you guys!
I'd like to challenge myself and give this build a try. I may be in over my head, but wanted to ask if anyone had any advice before I get started?
Is everything correct here? http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=47579&g2_GALLERYSID=ace1fcc31b7d711f6135f011d3090860
Is etching the best way to go? What size enclosure should I be looking to get? What effect does true bypass vs. Millenium bypass have?
I'm really looking forward to hearing your advice!
Alex
As you posted it does looks something like a Harmonic Percolator. There have been threads about the HP at this site IIRC.
With this type circuit were there is only one DC current path thru both devices the biasing/selection of transistors can be a little tricky.
The biasing of an grounded emitter transistor stage with one C to B DC bias/AC gain feedback resistor then having two in series from +9 to ground with the two emitters AC coupled to ground by the 47uf adds to the fun by how well it keeps the two gain stages from interacting with each other.
using the schematic from page one of this thread
Q7 bias really? 100K collector resistor with 100K volume control?
Q5 and Q6 1n4148 diodes C to B, why two, they are not AC coupled so how does the 2nd one conduct?
Quote from: Indiefuzz on August 25, 2012, 08:56:21 PM
I have been following this thread and must have read it 2 dozen times from start to finish. I have a lot of respect and admiration for you guys!
I'd like to challenge myself and give this build a try. I may be in over my head, but wanted to ask if anyone had any advice before I get started?
Is everything correct here? http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=47579&g2_GALLERYSID=ace1fcc31b7d711f6135f011d3090860
Is etching the best way to go? What size enclosure should I be looking to get? What effect does true bypass vs. Millenium bypass have?
I'm really looking forward to hearing your advice!
According to Chaosphere, over at the other forum, he's built it, and he claims it as verified.
Quoteusing the schematic from page one of this thread
Q7 bias really? 100K collector resistor with 100K volume control?
Q5 and Q6 1n4148 diodes C to B, why two, they are not AC coupled so how does the 2nd one conduct?
I can look at it again, but I'm 99.9% sure it's laid out that way. Don't ask me why though, I'm not that smart. :icon_rolleyes:
Verified diodes, and schematic is as advertised.
Vero is now VERIFIED!
Here is the updated vero, there were some additional corrections where caps were concerned. Also, I went with Russian Ge trannies on this build. I found that it was easier to find good trannies (read, NOT LEAKY AS ALL HELL), and they gave me a much beefier fuzz than the AC128/AC176 combo. I also teeter-toddered on Q5. I wasn't thrilled with the 2N2222 in this slot, but I found that a 2N3700 sounded better. Then, I tried a BC109B... NIRVANA! Anyway, you can really experiment with different trannies here, sky's the limit.
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/GEMINIVERO.jpg)
Here's a video of how it sounds. I'll tell you right now, the Ge side on my clone has quite a bit more fur on it, but you can dial that down a bit with the trimmers. Personally, I like more fur. I have two caps subbed here, since I didn't have them on hand, a 680nF, and a 120nf. The 680nF is 660nF (2 x 330nF's), and a 120nF is a 100nF.
As I mention in the video, the 1nF cap (C1, input to ground) is a Polystyrene in the original unit, and I used one here as well. I was never one to dwell on the mojo hype that one cap sounds better than another blablabla, but in this case, the difference is day and night. Period. I had a metal film brownie here to start, but it sounded dark and bassy. Pop a polystyrene 1nF in here, and wow! BIG difference. Besides, the one I used was from an old Farfisa organ, and it has "DUCATI" marked on it. Now how exotic is that.
Honestly, I like my clone better than the original. I mean, the original is great, but my clone just flat out rips!
Cheers,
D.
Great job Digi2t, good to see you verify for the Vero board guys... I will have to try this on my pcb trace... most of the parts are in, just waiting on a couple of caps. Looks like I need to get the right input to ground cap.
Would you let us know where you are sourcing your Russian transistors... I like more fur on tap as well...
Again, great job!!!
Tony
Quote from: dorrisant on September 01, 2012, 10:30:01 AM
Great job Digi2t, good to see you verify for the Vero board guys... I will have to try this on my pcb trace... most of the parts are in, just waiting on a couple of caps. Looks like I need to get the right input to ground cap.
Would you let us know where you are sourcing your Russian transistors... I like more fur on tap as well...
Again, great job!!!
Tony
Thanks Tony, I had a lot of fun with this one. It a VERY versatile fuzz. I can`t stress enough about the importance of the input to ground cap. Normally, I`ve never noticed a difference between caps, so I`ve always gone with whatever I`ve had on hand (read: cheapest). But, in this case, hearing is believeing. Lucky for me, that old Farfisa organ I tore down not long ago had a few of them. The difference is day and night. I can`t explain the science behind it, but the difference between the two 1nF caps is almost surreal. I even tested them on my cap meter to be sure, and both registered 1nF. Crazy.
As for the caps, Ebay is my friend here. The best ones I`ve found to date for fuzz are MP20B`s. MP16`s are OK as well, but lower gain. GT402`s are nice, and for NPN`s, GT404`s. As for consistancy, MP20`s are tops. They`re my fav`s in the 70 - 90 hfe range. GT402B (or V I believe) come in second for the 100 - 130 range. The GT404 tends to hover around 90 - 120. Gain ranges are generally fairly good, and leakage low to nil. Likewise for the MP16`s. GT402`s are a bit looser, and GT404`s tend to stray quite a bit. But, compared to what I`ve seen so far with AC128`s, and AC176`s, they`re way ahead of the game. Lots less garbage. They do exhibit more hair though. Fuzzier, with a bit more wooliness to the tone. Check out pinkjimiphoton`s Liberal Komrade, you`ll clearly hear it. Nonetheless, for the price, nothing you can`t deal with, either with a different cap, or the EQ.
Digi2t,
I have to ask... Would you be willing to part with one of those caps you found in the old organ? I'm putting together the final parts order for three different pedals and that is one of the few caps left to get.
If you don't want to part with any I can totally understand. PM me if you will.
That said, thanks for doing what you've done for this project. I for one will be hearing what this pedal has to offer very soon.
Cheers,
Tony
Quote from: dorrisant on September 01, 2012, 03:50:38 PM
Digi2t,
I have to ask... Would you be willing to part with one of those caps you found in the old organ? I'm putting together the final parts order for three different pedals and that is one of the few caps left to get.
If you don't want to part with any I can totally understand. PM me if you will.
That said, thanks for doing what you've done for this project. I for one will be hearing what this pedal has to offer very soon.
Cheers,
Tony
Sorry Tony. I've only got a couple, and I'm saving them for other projects. A quick search reveals that West Florida Components carries them, 25 cents each. I've dealt with them on several buys, no worries there.
Thanks man... I'll look them up!
Tony
Hey I put this vero together and I have a couple of questions/issues:
1. The tone switch as wired does not alter the sound at all.
--I'll try a different switch but Im not getting any change with this the way it is
2. My silicon switch alters the sound at both ends of the blend. The germanium switch barely makes any difference at either end of the blend.
3. Can you please reconfirm the transistor numbers on the vero layout? I figured it out by looking at the schematic but maybe you could make it clearly labeled.
4. My LED doesnt turn off with the millenium bypass wired the way it is.
---I think I'll just wire it for 3pdt true bypass.
So far I love this thing. I built it without the ferrite (I ordered some) and it sounds good but I'd like to get the issues figured out before I box it up.
Excellent work tracing and creating a layout.
Quote1. The tone switch as wired does not alter the sound at all.
--I'll try a different switch but Im not getting any change with this the way it is
I assume that your talking about the tone reversing switch. It`s only effective on the Ge side of things. The more you blend towards the Si side the less it effects the tone. When you`re completely on the Si side, it does nothing. This is as per the originals. I`ve verified this.
Quote2. My silicon switch alters the sound at both ends of the blend. The germanium switch barely makes any difference at either end of the blend.
Ensure that you`re using 3PDT switches that are ON-OFF-ON. Also verify your wiring between switches, the blend pot, and your vero. Everything works fine on mine.
*EDIT* - When the blend knob is working properly, the Ge gain switch, or Ge side as a whole, should not affect the Si side, and vice versa. For example, if you are completely over to one side, you can pull a tranny out of the other, and you should not hear any difference or drop out.
Quote3. Can you please reconfirm the transistor numbers on the vero layout? I figured it out by looking at the schematic but maybe you could make it clearly labeled.
I must admit that the tranny labels in DIY-Creator are a bit weak. I`ll superimpose more visible labels on them, and re-upload the vero.
Quote4. My LED doesnt turn off with the millenium bypass wired the way it is.
---I think I'll just wire it for 3pdt true bypass.
I`ve yet to verify this, I haven`t had time to. I`ll test it tonight, and get back to you on that one. It`s my first time using MB myself, so I`m still a virgin here :icon_mrgreen:. You can easily wire it for TB as well. That`s what chaosphere did, and that`s how it`s written up in his build doc. I`m just trying to keep it as per the original.... somewhat :icon_razz:.
On the transistor front, I`ve been playing with the Si side, and I have a new fav combo. BC547B/BC109B/2N3700 sounds amazing. This combo has more bite to it, really making it more distinct from the Ge side. This also adds more spice to the blend knob. The added bonus is that the Si side is much quieter as well at full gain. I don`t know what it is about 2N2222`s, I`ve never had much luck with them.
I`m also going to test an idea tomorrow, to replace the Lo/Med/Hi gain switches with pots. If my idea works, it will be the ultimate in dialing in the perfect fuzz tone. And it won`t take any more room in the box either. Stay tuned.
AAARRRRRRRGGGGGGHHHHHH!!!!!
Heads up everyone. The diode D4 for the Mill II bypass is the wrong way around on my initial verified version of the vero. I've updated the vero, but anyone that has downloaded the previous version, ensure that the cathode of the diode is going to +9v, AND NOT TO THE GATE OF THE 2N7000.
Not only will it not work, but you will instantly fry the 2N7000 upon application of power. If anyone has already built this, and the LED is staying lit all the time, this is the problem. Turn the diode around, and replace the 2N7000. Upon doing so, my LED works fine now.
Sorry everyone. It was marked correctly on the schematic, but it fell under my radar when I drew up the vero. I've re-uploaded the vero, with the diode facing the right way, so please double check your version. Everything else is fine.
As for my idea of using pots to work the gains, rather than switches, it dawned on me that there is DC flowing here. Any movement of the pot will produce noise in the circuit. I'm not sure if there is a way around that, but I don't feel like doing a redraw here. There's enough to this baby as is, I'm more than happy to live with the switches.
To make omlets, you must break some eggs!
I fixed the LED issue with turning the diode around and replacing the mosfet.
I fixed the germanium switch issue by putting an npn germ tranny in for Q3.
I messed up and had a pnp in there.
Now it sounds BADASS!!!!!!!!!!
This is a MUST build for everyone. One of the coolest fuzzes Ive done in a long long time.
Thanks for the great work tracing and doing the layout.
Quote from: onthetundra on September 12, 2012, 07:34:56 PM
I fixed the LED issue with turning the diode around and replacing the mosfet.
I fixed the germanium switch issue by putting an npn germ tranny in for Q3.
I messed up and had a pnp in there.
Now it sounds BADASS!!!!!!!!!!
This is a MUST build for everyone. One of the coolest fuzzes Ive done in a long long time.
Thanks for the great work tracing and doing the layout.
No problem. And guess what... I have a WOW Signal fuzz on the way to my work bench. Stay tuned for another layout. Have fun with the Gemini, it really is a "Fuzz for all seasons". Glad you got the bugs worked out. Please try an post a sound or video clip if you can.
Cheers,
Dino
You are the Spaceman source! Please PM me when you start the WOW thread!
Tony
Quote from: dorrisant on September 13, 2012, 10:31:01 AM
You are the Spaceman source! Please PM me when you start the WOW thread!
Tony
No problemo. For those who are curious, there's finally a video out...
Jimi... does this one tickle your ears brother? :icon_mrgreen:
OK... clone is DONE!!!
I've done some surgery in my time, but I think this one really tested my wiring/soldering skills. It was tighter than a frogs a$$ in there, and that's watertight!
(http://imageshack.us/a/img43/2724/dscf3031uu.jpg)
(http://imageshack.us/a/img339/3105/dscf3026hc.jpg)
(http://imageshack.us/a/img440/4051/dscf3030j.jpg)
(http://imageshack.us/a/img692/8523/dscf3029fq.jpg)
(http://imageshack.us/a/img138/3278/dscf3028y.jpg)
(http://imageshack.us/a/img89/2923/dscf3027rz.jpg)
My first Millenium Bypass too. I'm quite pleased with it. Customary video will be forth coming soon.
Nice... It looks so vintage!
I love the look of those old Russian cans... I'm waiting for mine.
Tony
Update on the Millenium bypass.
R28 should be upped from 1.21K to 4.7K. This is the current limiting resistor for the LED. I believe there's too much current flowing through the diode, and it gets hot. My LED (super bright red) was going on and off. Probably the heat/cool cycle of the diode. Also, I was getting a pretty bad pop when I was switching the effect. With a 4.7K, both problems disappeared. I suppose that the original uses a 1.21K in relation to the type of LED that they are using. If you're using super brights, I recommend a 4.7K resistor.
I've updated the vero in the Gallery.
Video will be here on Monday.
Cheers,
Dino
OK folks, video is here. But before we get to it, I have to lay down some more info.
First off, I was having a problem with the sustain on the silicon side. Actually, I narrowed it down to Q4. Although it's a 2N2222A in the original, an I had even tested a few different BC type transistors, the sustain wasn't anything to write home about. Voltage wise, I wasn't getting close to the voltages that the original was giving me on Q4, coming up short on the collector by more than 1/2 a volt. After a lot of head scratching, and sifting through a ton of different transistors, I finally found a correlation between the gain of the transistor, and Q4 collector voltage. With a 2N2369A (see Axis Face) in this slot, with a gain in the mid-60's on the Peak meter, I managed to not only meet, but surpass the collector voltage by .2 volts. So, high gain here, no good. Higher gain was killing my collector voltage. I figure if I had one in the low 70's, I'd be spot on. I did keep the BC109B in Q5, and the 2N3700 in Q6. I also ditched the 120nF cap after Q6, for the 100nF that I had in there during testing. This was a personal issue, my ears said "better".
Secondly, setting up the voltages of the Ge side. I had to do a bit of reading on the Harmonic Percolator. Especially where the HP's Q1 emitter to ground, and Q2 collector to +9 resistors are concerned. It dawned on me then why they used the particular trimmer values (25K and 100K) in the Gemini. I decided to set my two trimmers, as if I was dealing with an HP, to 20K and 91K. Plugging in the unit, I found two things; A) My Q2 and Q3 voltages were WAY off from the original, and B) with the Ge gain switch on high, I was getting oscillation. With the DMM on Q2 emitter, I started dialing the 25K trimmer in small increments, reducing the voltage. This would change the pitch of the oscillation, but not eliminate it. Slowly dialing the 100K trimmer in the same direction, I could then kill the oscillation. Dial the 25K a bit, oscillation comes back, kill it with the 100K, and so on. I kept on doing this back and forth ballet, in small increments, until I got Q2 emitter to .5v below Q1 emitter (as per the original), and had no oscillation. At this point, with the Russian trannies, I'm about +/- 10% within the voltages I get from the original unit.
That's it. A bit of fanagling, but with some CDF (Common Dog F*ck), we got 'er licked. On to the vid. Enjoy.
Quote from: digi2t on June 07, 2012, 07:12:23 PM
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/DSCF0977.jpg)
Would it be possible for someone to post the back of the lower board? Trying to fit it all in a regular size enclosure
and a straight copy of the pcb is the only way. This one is far more daunting than anything I've ever worked on. :icon_eek:
Any attempt I would make to rearrange the circuit would end in disaster.
Sorry, the best I can do is this;
(http://i214.photobucket.com/albums/cc196/digi2t/Gemini%20Fuzz/Geminilower001.jpg)
Since the pots and switches are soldered directly to the board, pictures of the trace side were quite useless. That's why I drew it by hand. Also, the lower board is double sided, the red lines indicate traces on the component side of the board. Your best bet would be to redraw it on the computer, using the pin spacing of the pots and switches to scale things. FWIW, the lower board is the same width as the upper board. Using the spacing of the stand-offs (1 through 7) to scale the lower board should help as well.
^Thanks ;D. I'm about to go transistor shopping. Can you recall what were the gain values (Ballpark figures) of the original transistors and of the ones replaced them with? I like what you achieved with the silicon side, The germanium side I will test as many possible candidates for high gain as I can while still retaining good cleanup.
I have heard that the Gemini III does not clean up well so perhaps it is a factor of the design rather than the transistors. I have a Mercury III and an Aphelion but sadly no original Gemini III that I can compare with.
Quote from: zetamkiii on February 12, 2013, 01:18:35 AM
^Thanks ;D. I'm about to go transistor shopping. Can you recall what were the gain values (Ballpark figures) of the original transistors and of the ones replaced them with? I like what you achieved with the silicon side, The germanium side I will test as many possible candidates for high gain as I can while still retaining good cleanup.
I have heard that the Gemini III does not clean up well so perhaps it is a factor of the design rather than the transistors. I have a Mercury III and an Aphelion but sadly no original Gemini III that I can compare with.
Gain values of the original transistors?
BWAAAAAAHAAAAAHHAAAAAHHAAAAAHHAAAAAA!!!!
Sorry. There was no way in hell that I was going to pull the transistors out of the original unit. Your best bet is to study the Harmonic Percolator and company, and follow recommendations for transistor gains in those circuits. I'll see if I wrote down the gains I used for my unit, but I don't think I did.
As far as cleaning up is concerned, using the silicons that I did, on full silicon, it cleans up really well. Better than the Ge side. I believe I demo'd this in my video.
I'll see if I can find those gains for you.
Just an estimate would do.
Quote from: zetamkiii on February 12, 2013, 06:30:21 PM
Just an estimate would do.
Your in luck. Look here; http://www.diystompboxes.com/smfforum/index.php?topic=97493.msg856308#msg856308 (http://www.diystompboxes.com/smfforum/index.php?topic=97493.msg856308#msg856308)
That's my vero layout, and the Ge transistor gains that I used are on the left hand side of the layout. These values are in my clone, and my voltages are almost spot on to the original. Mine sounds better though :icon_mrgreen:.
I knew I had put them down somewhere. Just had to dust off the ole thinking cap.
Any clue about the silicon side values? Doesn't need an NPN at the end of it too does it? I'm just trying to find an acceptable
range of the first, second and third transistors for these parts while I gather everything for a breadboard.
For Q5 you say mid 200's. A pretty big difference in gain from the GE side.
The impression that I got from comments and demos was that:
Ge1 is the lowest gain stage,
Ge2 and Si1 were a similar gain,
Ge3 and Si2 were also similar gain,
and Si3 was a gain stage above Ge3.
So I was going to base my hfe values according to that basic idea.
Thankfully this one isn't as finicky with the hfe as the wow signal.
Edit:Ah the silicon side is all npn...
sorry to bump such an ancient thread, but i need one of these in my life.
mouser has part# 42TL019-RC backordered until july and i dont want to wait that long.
all i have here is # 42TL018-R and i am certain that wont work. is there a workaround available that any of you has seen? or any for sale anywhere that isn't mouser?
Their first delivery date is 3rd July, that's only about 5 weeks away
:-)
sorry to bring this thread up again, but i've looked all over and cant tell the difference between a DPDT on-off-on and a DP3T on-off-on. it says DPDT on-off-on in the BOM...
I am also exhuming this thread/this is my first diystompboxes post so apologies for that.
Anyway, I have completed my build on vero - thanks to all involved in the discussion and tracing because it all came in handy!
The enclosure has since been painted hammer finish copper:
(https://40.media.tumblr.com/268c3dd7b2f4beb9ba8623e33e433c31/tumblr_ntmj51b32E1qkzl6yo1_1280.jpg)
and a blurry shot of the inside:
(https://41.media.tumblr.com/feee212be5e85bb97740bb7dd8692f18/tumblr_ntmj51b32E1qkzl6yo2_1280.jpg)
Germanium transistors are Sanyo 2SD187 for the NPN, and MP20Bs for Q1 and Q2.
Silicon transistors are as stated on the vero layout.
My main issue is with the germanium side output - it's significantly quieter than the silicon side. It is also 'looser' than my real Gemini III. Any suggestions on tweaking it to be louder on the Germ side? I'm not sure where to start.
What are your voltages for the Ge side? It might only mean that you need to tweak the bias trimmers a bit to raise the volume. See here for adjusting the Ge bias; http://www.diystompboxes.com/smfforum/index.php?topic=97493.msg868878#msg868878 (http://www.diystompboxes.com/smfforum/index.php?topic=97493.msg868878#msg868878)
I found that adjusting the Ge bias trimmers generally helps even out the volume difference, unless the transistors are too leaky. In my unit (if memory serves me) I believe the Ge side is slightly louder, and more wooly, whereas the Si side is a tiny bit lower, but the fuzz is more aggressive, along the lines of a BMP.
Thanks digi2t!
I will report back with my previous voltages and then tweak as suggested. So set it like the HP, then work backwards from there... very good.
Appreciate the guidance.
charles
Well, your suggestion seemed to work! My biasing for the Germ side was just totally off. I am still kinda out of the ballpark with voltages on Q3, but it sounds good. Q2 is within 10% of the original voltages. Happy! Getting a highish pitched whine on the silicon side and it's a bit noisy, but that's probably because I didn't shield the wires and the lid is currently off heh.
Thanks man! YA RULE.
Quote from: chuckd666 on September 19, 2015, 12:20:38 AM
Well, your suggestion seemed to work! My biasing for the Germ side was just totally off. I am still kinda out of the ballpark with voltages on Q3, but it sounds good. Q2 is within 10% of the original voltages. Happy! Getting a highish pitched whine on the silicon side and it's a bit noisy, but that's probably because I didn't shield the wires and the lid is currently off heh.
Thanks man! YA RULE.
What transistors are you using?
I have a couple MP20Bs for Q1 and Q2, and a Sanyo 2SD187 for the NPN Germ. The Hfe for the NPN is a little lower than I assume it should be. It was around 60-70 I believe.
Yeah, if you use what I prescribed on the vero for Q3 gain (100 - 115 hfe), that should bring your voltages into line. You should be able to get pretty close to the original voltages all around.
Yeah I figured that must be the culprit. It sounds good at the moment, but might just have to get a bunch of NPNs somehow. Thanks again for the help. A/B'd with my real one it sounds pretty on par.
Hello all,
I'm having some slight voltage issues with my Fuzzimile (spaceman gemini iii) build, and I can't seem to find the cause, yet.
Am using the prescribed Russian transistors all within the defined specs. Checked resistors and caps twice.
Everything works, I'm just trying to get to the right biasing point. I can't manage to get Q3/Q6 right, there are much less variation between EBC in my readings, and trimmers can't help. Q5 collector behavior also seems odd.
Voltages are as following (reference voltages from Digi2T in brackets)
Supply: 9.31V (9.05)
Q1
MP20V - Hfe: 84; Iceo:82uA
E: 2.332 (2.044)
B: 2.200 (1.916)
C: 1.440 (1.452)
Q3
GT402V - Hfe:128; Iceo: 95uA
E: 1.720 (1.336)
B: 1.665 (1.174)
C: 1.652 (0.805)
Q6
GT404V - Hfe: 103; Iceo: 270uA
E: 1.720 (1.336)
B: 1.766 (1.416)
C: 1.779 (1.702)
Q4
2N2222A
E: 1.731 (1.238)
B: 2.205 (1.914)
C: 2.286 (3.246)
Q5
2N2222
E: 1.585 (1.726)
B: 2.186 (2.209)
C: 1.775 (2.358)
Q6
2N3700
E: 1.183 (1.136)
B: 1.759 (1.726)
C: 2.291 (2.358)
Q7
2N5088
E: 0.159 (0.159)
B: 0.707 (0.709)
C: 1.669 (1.507)
Any light that can be cast on these voltage variations is appreciated.
Picture shows the transistor in the build.
Thanks,
Zoot
(https://i.postimg.cc/TpRCYh3d/996-ECC69-2-E2-C-47-C9-8-C25-7-C3253-E9-D136.jpg) (https://postimg.cc/TpRCYh3d)