Soviet "Buster" fuzz copy - need help!

[salwa]

Hello!

So, after few successfully (and few unsuccessfully) builds-by-numbers, I decided to go further - to make a clone of something by myself. Of course, very quickly I found out, that my knowledge in electronics is next to nothing and, in fact, I don't understand, what I'm doing
But having an obscure soviet fuzz with schematics was too tempting...
So I made a layout, here it is:

http://www.aronnelson.com/gallery/main.php/v/salwa/Buster.gif.html

You can find schematics here:

http://www.aronnelson.com/gallery/main.php/v/rnfr/easternblocdiy/kazanbooster.jpg.html
http://www.aronnelson.com/gallery/main.php/v/rnfr/easternblocdiy/kazanbooster2.jpg.html

To my amazement, the thing works, but not without issues. So, here is the part when I have to swallow my pride and ask for help

First of all, it does not sound as good as original - it's very loud, picks every little movement you do on strings and produce a wall of sound - not very pleasant. Could it be matter of transistors? I've used ac 128, but, having minuscule experience in electronics, couldn't find a way to measure gain of originals without desoldering them - and I don't want to do it. Any ideas?
Second thing is strange resistor R8 - it's on schematics, but not in the part list. But I found out, that putting lower than 1Mohm resistor in that place results in silence and overheating transistors and that the whole circuit is better without it. Also, but I knew that earlier, that the only purpose of R16 is lowering overall volume, so it's better to omit that one.
My third problem is diodes - I used germanium and silicon diodes and couldn't hear the difference. My question is - do their material (Ge or Si) plays any role in sound of the unit?
Fourth problem is the strangest. I wasn't sure, how to orientate electrolytes, so I socketed most of them (C4, C7 and C8). But then I found out, that their polarisation makes no difference - I could put them backwards and still get the sound. How could this be possible?
Minor problem was C6 - original parts list wanted something rather unspecified. I found 0,1 uF works best.
I will be very grateful for answering my questions. I want also to excuse in advance for my ignorance in electronics (humanist here...) and my English - it get a little rusty since I finished my schools.

[salwa]

bump?

[petemoore]

  You have a working original there?
  Take voltage measurements of the transistors pins to use as a guide

[jrod]

Thanks for the layout!!!

I have been curious about these schematics ever since RnFR posted them. There is one in there that looks just like a Fuzz Face and Mini Booster, too.

I found specs on the transistors MP39b and MP42b. MP39b looks to be a very low gain transistor (20-60 Hfe) and MP42b also looks to be low gain, too (45-100). So, this circuit must be tuned and biased for lower gain transistors. Here is the spec sheet http://www.evita.lt/getPdf.php?id=16976

Here is a link to RnFR's site for more info on this circuit: http://apocalypseaudio.blogspot.com/search?updated-min=2008-01-01T00%3A00%3A00-06%3A00&updated-max=2009-01-01T00%3A00%3A00-06%3A00&max-results=7

I'd like to know more about the missing R8 resistor for the value and what it's purpose is in this circuit. So, if anyone knows....

[salwa]

Thanks for your responses, guys!

First of all - I've made mistake on the layout (swapped the pots) - now it is fixed. I also measured voltages of original pedal:

T1: E - 8,15
      B - 8,03
      C - 3,24

T3: E - 8,16
      B - 8,01
      C - 6,88

T4: E - 7,08
      B - 6,89
      C - 2,66

Battery had 8,22V. Maybe they could help someone. I've managed to find some old low gain transistors (ADP672), but the copy still does not sound as good as original. Voltages are similar, but about 0,5V higher. Could this be the problem? Also I still don't know what to think about that electrolytes and diodes. Probably should read more...

[rnfr]

hey guys.  cool to see someones getting some use out of the crap i throw at the internet! :icon_wink:i never did get around to workin on this thing, but you have definitely sparked my interest again.  especially since you actually have the original unit to compare to!  i'll try and get this breadboarded as soon as i can and give it a shot.  maybe try that 1M R at R8 again? the only thing i could think of was that they adjusted it to bias Q2, so maybe try working that around a little. i've got a few different kinds of soviet trannies, including som very low gain gt311e's, so that might help,too. i think i have a vero layout somewhere that i could post as well.  i'll check when i get a chance since right now i'm at work.

--

hey, if you haven't already, try implementing the resistors at the end of the circuit.  it might tame it a little and give you what you are looking for.
you should check the circuit to make sure that it matches the schematic.  are the transistors correct?  often times, factory schems can be wrong.
and i would stick with ge diodes, it is likely that was in the original design.

[salwa]

Hi again!

First of all - thank you, guys, for your input. I played a little more with the circuit and this is what I found out.
First - voltages of my copy were 0,5v higher than in original, because - guess, what - one of the batteries provided 0,5v higher current than other (stupid me, should've measured it first before posting, doh...).
Second - of course, you were right, rnfr, it was bad idea to get rid of that resistor at the end of the circuit. But the 150K was too much. Then I remembered, that my friend, who initially fixed Buster after I bought it, replaced it with 82K resistor (doh again, how could I forget it? nevermind). So did I and now the sound is tamed.
Third - I still don't know, what to do with that R8 resistor. Anything lower than 1M cuts the sustain in a very bad way (gating is propper term I think), but I didn't noticed any difference between 1M-option and no-resistor-at-all-option. Original Buster have 10K resistor there. Maybe it depends on what kind of transistors you use - I don't know, my knowledge is pretty limited.
Fourth - I wasn't sure about C6 value (as you can see on scans of manual - this is unclear). I measured it and it is about 7,6nF. I tried to put there 10n and 100n and liked the latter better, bud I think the best option is socket and your ear.
Anyway, the copy is working now. It still doesn't sound exactly like original, it's more buzzier, but it's nice fuzz after all.

That may be the end of this story. But it's not.
I finally decided to do something for humanity, fight my fears and disassemble original unit. And after that I confronted it with schematics. First what struk me - if you paid attention to the schematics, you've probably noticed strange numeration of parts. It came out, that all the "missing" parts (diodes 1 to 3, transistor 2, C3 cap, resistors 3, 4 and 6) have their places on the board. What's worse, some of the parts, that are on the schematics, are omitted, and some of the "missing ones" are present. I looks like that
- R7 is missing (empty slots)
- R3 is present (measured 7,4K, first leg touches the line that connects nonpresent T2 base, first leg of nonpresent C3 and C1, second leg touches line between R5, R9 and R11; it's on the top on schematics)
- R6 is present (measured 4,4K between C4 positive leg and ground)
- R4 is missing (empty slots, between ground and C4 negative leg)
- R2 is missing (empty slots)
- diode 1 - jumper (between C1 and ground [positive end here])
- diode 2 - jumper (between T1 emitter [positive end here] and second leg of nonpresent C3)
- diode 3 - jumper (between C4 positive leg [positive end here] and T3 base)
- transistor T2 is missing (emitter is connected between second nonpresent C3 leg and D2 negative end; base is connected to first C3 leg and R3 first leg, collector connected to second R3 leg)
- C3 is missing
Now I'm dumb. I'll try to update schematics and study it, but it's getting late. I hope this may help someone.

[rnfr]

wow. i'd say that a bit different!  looking forward to seeing the new schematic.  thanks for all of your work.  i really appreciate it.  just make sure that when you are measuring your resistors, you have them desoldered from the board, or else you won't get accurate readings.  with capacitors, it  may be possible to measure them in the circuit, but i'm not sure.  this of course will take a bit more work, and be a bit more of a risk to you pedal, but unfortunately, it's the only way to get accurate readings. 

[salwa]

So, I desoldered some of the resistors (luckily, some of them were clearly labeled), measured them and tried to update schematics. Here is effect of my work:
http://www.aronnelson.com/gallery/main.php/v/salwa/real+buster.GIF.html

Still, I'm not sure about polarity of some of the capacitors. Also, please, excuse my drawnings, I'm more of the musician I think...

[rnfr]

cool!  are all the cap values the same?  did you try building up the new schematic?

[salwa]

I'm terribly sorry - I've messed it up. After closer examination I found out that everything looks like in original schematics - just the names of parts and their places are different. So I've uploaded final (I think) version of schematics in place of former. As you can see it looks almost the same, the only differences are resistor numbers and values. I think some of the weird values are due to horrible tolerance of soviet parts (10% I think), so 910K is probably 1M and 7,5K is probally 6,8K. Just R11 is definitely different: 1,2K instead of 2,4K. Caps are like in specification, only C6 is measured 5400pf (without desoldering, but it should be OK), so I think you can put 4700pF there.
Once again I'm sorry for this mess. I can see, that whole "reverse engineering" is difficult art. I'll post an OK layout (with right polarity of capacitors) as soon as possible, probably in few hours.

[salwa]

Hello once again!
I think I finished my business with Buster, here is link to propper (I think) layout:
http://www.aronnelson.com/gallery/main.php/v/salwa/buster.gif.html
I would be very thankfull if someone build it and let me know, if it works. It should, but I can't say that - unintentionally I destroyed one of my low Hfe Ge transistors and can not check the circuit.
Cheers!

[jrod]

Hey Salwa! Thanks for your effort on this project! I am going to try this out on the breadboard hopefully by this weekend and I will post my results as soon as I get it up. I won't be able to do the vero layout right now, but I do want to give it a shot.

Again, thanks, and I will let ya'll know my results.

**EDIT** I just realized that I don't have the correct pot values to breadboard this, but I will try as soon as I can get them.