Univox Superfuzz weird voltage ratings

[Epameinondask]

Hello there. I have been building the superfuzz on my breadboad and I have a very weird problem. First time I breadboard it I had a weird output, like a misbiased transistor. Then I touched two resistors and created short and when I let them go the fuzz worked for about 4 seconds and then the same misbiased sound came back. After that I tweaked some components and boom it worked perfectly.

Then comes the even more weird behavior of the circuit. I put it together again in order to try some mods i had found and it never worked again. It behaved again the same way (misbiased sound and 4 secs of working after i did the short thing). Then i noticed that if i rolled the volume on my guitar back a little bit the fuzz was working but the sound again was not exactly like it should and when I didn't play the guitar a hum( like something is not grounded ) was present. After that i rebuild it third time. No luck again. Fourth time i did it there was an other problem. It sounded like an fuzzy overdrive, but over than that no hums or misbiased sound.

I did all the troubleshooting i could. I triple checked the cap polarities and the schematic every time I put it together. Then only thing that seems to point out something is the voltage ratings. I found on the web what the voltages of every transistor should be and I am a little bit of.

Regular ratings:              My ratings:With 9.23 volts power supply
C B E                                   
Q1 6.01 .66 .117            Q1 5.07/0.496/0.013
Q2 8.88 6.01 5.41          Q2 9.22/5.06/4.46
Q3 6.23 3.27 2.72          Q3 8.16/1.807/1.248
Q4 3.1 1.7 1.11              Q4 6.76/1.109/0.540
Q5 3.1 1.67 1.11            Q5 6.76/1.109/0.540
Q6 3.71 1.21 0.59          Q6 7.40/0.789/0.216

All my 2n3904 are hfe:190+ but below 200. What could possibly be the case??? Caps?? Checked them and they're 10uf more or less. Thank again for your time. Cheers 

[digi2t]

Could you link the actual schematic you're using? I know of at least one schematic on the web that has an error in it, so... just sayin'.

[Epameinondask]

I doubt that the schematic is the problem because i have got it to work perfectly following these schematics, but these are the schems
-http://s76.photobucket.com/user/IvIark_2006/media/Layouts/Schematics/UnivoxSuperfuzz.gif.html
and the polarities:
-http://s215.photobucket.com/user/guyatron/media/superfuzzMyMods.jpg.html

[digi2t]

This reminds me a bit of Pauly's Colorsound Vocalizer build. He went nuts trying to figure it out. Long story short, it was one wrong resistor band color that haunted the whole thing (i.e. 220K instead of 22K).

Touching it with your fingers might change the resistance enough to make it work. I'm spit-balling here.

[Kipper4]

Thread jack

So it's an booster amp, buffer, amp, some sort of differential with a currant mirror ? Which presumably is a clipping section also. ,switchable tone section and output amp.

Right ?

[duck_arse]

your Q3 base is way low. check those two base resistor values, with your meter. the volage drop on the E resistor should be similar/same as the Vdrop on the C resistor, so check those as well, WITH YOUR METER.

[Epameinondask]

your Q3 base is way low. check those two base resistor values, with your meter. the volage drop on the E resistor should be similar/same as the Vdrop on the C resistor, so check those as well, WITH YOUR METER.

What do you mean by checking the base resistors? Check the resistor values? I checked them they seem fine 220 and 150 kohms.

[duck_arse]

I mean yes, test the resistance of the two base resistors, one should be 220k and the other 150k. measure the resistances on the board, see what they say.

just looking at some numbers, if the cap between the wiper of the 50k expander pot is not isolated from the base resistors by the 10uF cap (I'm looking at the unicord schem), the parallel resistance of 150k and 50k would give, with 220k and 9V supply, a base voltage of ...................

[edit :] fixed 150k value

[Epameinondask]

When you say on board you mean having them on the breadboard with currect flowing through them? Because when i did the multimeter read on the 220k resistor something like 6.2 mohms which i think is crazy. Sorry to bother you with newbie questions 

[Rob Strand]

I suspect you have swapped C and E on the transistor pin outs.

[Epameinondask]

I suspect you have swapped C and E on the transistor pin outs.

I followed  this pinout:
https://www.google.gr/search?q=2n3904&es_sm=93&tbm=isch&imgil=PmMmjkEGiVHRuM%253A%253BElnDfPwQbuBC1M%253Bhttp%25253A%25252F%25252Fwww.ecs.umass.edu%25252Fece%25252Fm5%25252Ftutorials%25252Fmultiple_LEDs_tutorial.html&source=iu&pf=m&fir=PmMmjkEGiVHRuM%253A%252CElnDfPwQbuBC1M%252C_&biw=1366&bih=643&usg=__Orf9eBKbBMCcyoiU0-JeEAz15sA%3D&ved=0CDYQyjdqFQoTCPT1tL-fqccCFQNuPgodHC4MMA&ei=LDnOVfSvNoPc-QGc3LCAAw#tbm=isch&q=2n3904

I am 100% the C and E are correctly positioned

[Rob Strand]

Does this agree with your pin out?
http://cdn.instructables.com/FYH/0X87/H3W56L9Z/FYH0X87H3W56L9Z.LARGE.gif

Are you sure you are looking at the transistor with the correct orientation (looking from top or bottom)?

As much as I believe you, all the voltages you posted are very much like a transistor with a gain of around 5; I simulated the circuit in PSPICE with a gain of 5.   A gain of 5 is pretty much what you get when you use a transistor with C and E reversed.  (The "good" voltages correspond to gains of 100 to 200).

I don't know what the problem is but it is definitely related to the transistor gain or pin out.

You could measure the transistor gain using the pin out you think is correct then measure it again with the CE pins reversed.   The wrong pinouts with give a gain of say 2 to 10 and the correct ones say 90 to 200 (...whatever a number in the hundreds).

[Rob Strand]

Sorry to bother you with newbie questions 

If you are a newbie maybe some of your resistor values are off by a factor of 10 because you have misread the bands.  It's easy to screw up the 5-band resistors as the multiplier band is different to the 4-band resistors.

[duck_arse]

When you say on board you mean having them on the breadboard with currect flowing through them? Because when i did the multimeter read on the 220k resistor something like 6.2 mohms which i think is crazy. Sorry to bother you with newbie questions 

no, never measure resistance with power connected. the meter puts a measure of volts across its test leads, the circuit power only confuses the reading, as you have found.

if you are on the breadboard, you can isolate each section from the next and check stage voltages. on this huge circuit dia:



disconnect the 10uF before and after the expander pot to isolate Q1/2 from Q3, then the 10uF before the 470R's and the 10uF before the diodes to isolate the Q4/5 rectifier pair, and the 10uF (you might spot a pattern, here) after the balance pot to isolate that stage. THEN do the measures again (power-off resistances and power-on voltages) and if your voltages have changed, you have isolated the problem, more or less.

[duck_arse]

Thread jack

So it's an booster amp, buffer, amp, some sort of differential with a currant mirror ? Which presumably is a clipping section also. ,switchable tone section and output amp.

Right ?

kipper - first 2 Q's look like a feedback pair, then a phase splitter, rectifier pair, recovery amp.

I have a folder named "diffpair", full of circuits mostly wrongly sorted. that which looks like a differential pair is a pair of rectifiers instead, as in the superfuzz, the dynacomp, the slow gear and others. but! in the bd-2, the od-3 and the fz-2 there are differential pairs, in some cases a pair of pairs, and the fz-2 has the pair paired with a rectifing pear.

and seeing as the output is f2, I'd guess they were a full-wave rectifier.

[edit :] un-oops an 'or' to 'of'.

[Kipper4]

Thanks DA. I missed so many paths and nodes there. I can see now thanks for pointing it out,
Rich