BIG MUFF PROBLEM

[jozabroz2000]

Hi guys,

this is my story.
I have build Big Muff Violet Ram's version from GGG  (my 3th muff project) and when I turn tone pot back, sustain (drive) start normally but after a second it cuts off.
same thing with tone pot all the way up but not so drastic like with tone pot back. it has some kind of tremolo cutting phases after some time of sustain.
already checked readings and try to replace transistors with no success!
what else could be wrong except transistors.
i hope that my explanation is good enough because my English is not perfect!

thanks in advance

[jozabroz2000]

just want to add that it cuts off only drive - i still can hear some kind off muted sound

thanks!

[Mike Burgundy]

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

[jozabroz2000]

link to layout:
http://www.generalguitargadgets.com/pdf/ggg_bmp_ram_lo.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

link to BMP Instructions (voltage reading reference and photos):
http://www.generalguitargadgets.com/pdf/ggg_bmp_instruct.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

no mods!
reading are close to pdf above except Q4:
Collector 3.5
Base 1.6
Emitter 1.2

sorry but it is difficult for me to explain in English

thanks

[Mike Burgundy]

The problem you're describing sounds like gating, which is usually related to a mis-biased transistor. C between 3 and 4.5, base a diode drop above emitter - looks okay. It's a humongous guessing game, so in the words of Johnny5 - "Need Input".
It'll help if you post all voltages, and probably some pictures of your build as well.

[jozabroz2000]

9.51 volt battery
Q1
Collector 4.09
Base 0.63
Emitter 0.04
Q2
Collector 4.27
Base 0.65
Emitter 0.06
Q3
Collector 3.9
Base 0.62
Emitter 0.04
Q4
Collector 4.69
Base 1.75
Emitter 1.28

it is in the box at the moment so the only pic available now is layout (don't know how to attach it)
all soldering checked twice!

thanks again

[jozabroz2000]

one more correction!
it doesn't cut drive! drive is still there but sound is a lot, lot muddier (so i thought it was cleaner - it is so muddy that i thought that there is no drive)
it is happening with tone way up but in intervals (it sounds like tremolo )
I can also hear oscillations when not playing (noise oscillating)

here is a pic:
http://postimg.org/image/seh7fwamv/full/

sorry and thanks again

[LucifersTrip]

just to be clear....are the voltages the same before and after the cut?

[jozabroz2000]

sorry but I don't understand you!
what cut?
if you are talking about cut that i have spoke about, i can not measure it (need more hands to measure it while i am playing)

[jozabroz2000]

I build another one and same f.... problem
listen this

vol 1/2 - tone full back - sustain full
https://soundcloud.com/iconbih/1-1

vol full - tone full back - sustain full
https://soundcloud.com/iconbih/vol-full

recorded direct in to PC mic input (lot of noise) - sorry no time to setup my audio card
only thing what I didn't change is wiring but I place wires same f..... way like before when everything was OK

http://postimg.org/image/seh7fwamv/full/

[LucifersTrip]

sorry but I don't understand you!
what cut?
if you are talking about cut that i have spoke about, i can not measure it (need more hands to measure it while i am playing)

yes, exactly...it would tell you if something is happening in the circuit when the cut happens that you spoke about

I'm sure you can figure out some way to rig something to measure while playing.

[jozabroz2000]

did it!
no voltage changes!
have you checked my links?

[Mike Burgundy]

alligator clips are brilliant for this.
An audio probe (search the forum) is also a great tool.
The sound is not gated like I suspected (thanks for the samples, great help!), the voltages look okay. There's a LOT of noise there (was it boxed ate the time?), and there appears to be very little signal on the input. Maxing out sustain and volume should make the thing go loud as anything - this may account for the noise, but apparently there's almost no signal getting into the ciruit and/or past one of the stages. to me it doesn't sound as if there's something changeing in the transistors bias, more like the circuit is cranked to get a crappy signal through and it's modulating all the noise that comes with that much amplification.

When you rebuilt it/built a second one - what parts did you actually build anew, and what did you re-use? did you make a new pcb but use the same wiring harness and box? The fact they share the same problem makes it very likely the fault is in something you used again (can be *everything* from the guitar, cord, wiring harness, etc), OR there is a common error - such as getting the transistor pinout wrong.
Most likely I think are wiring error in whatever you used again, or a short when mounting it in the box.

So - what is common to both attempts?
-eliminate the common bits one by one as cause (check the guitar and cable to see if they are ok, then move on to the bits of the builds. measure wire connections for continuity, make sure ground is done all properly connected)
-try it without the box
-try one wired afresh without switch and just the battery and in/out connected directly to jacks. Connect 1)board ground, 2)out ground and 3)battery - all to the ground lug on the input jack. Ignore ground switching for now, don't use the ring connection, hardwire all ground connections to this ground lug.
-measure if the pots are behaving like they should from the board, as well as from the pot terminals
-etc
Debugging this sort of stuff is a pain, but keep at it - you'll get it eventually.

[jozabroz2000]

when i built second... only box, switch and dc socket were used from 1st one. new pots, new board, new cables...
when i recorded, it was boxed without bottom cover! (it is noisy, but not that much when i play (guitar-pedal-amp)) just sent you clip to hear what kind of problem is
i will try your advice and test it without box and switch

[jozabroz2000]

ok
test it without box - same problem
and it is not guitar, cables...(that was first thing i checked)
problem on the board definitely

here are pics. hope someone will spot something!

http://postimg.org/gallery/a5n70692/fe25000c/

[LucifersTrip]

test the signal after each stage to see where the problem begins....
http://www.pisotones.com/BigMuffPi/psst/schm-ram-violet.jpeg

hook the output after the .1's

I just use a grounded output jack, but as suggested earlier, the audio probe is what many use since you may want to check a spot with no cap.

http://www.diystompboxes.com/pedals/audioprobe.jpg

[Mike Burgundy]

Strange that two different builds have exactly the same problem.
Okay - recap:
-you've built 2 muffs before that definitely do NOT do this, right?
-two consecutive builds now share the same problem
-they are completely different builds and share no components (aside from the switch I think? Tried wiring without the switch yet?)
-voltages look ok.
-you've made a soundsample that seems to indicate a problem - there's a catch though. It is entirely possible this gives a wrong impression - there's so much gain that it's very hard to tell what is going on with all the noise. The way I hear that sample the noise is a bigger issue than the tremolo thing. But that's possibly because I don't have the unit in my hands and cannot compare it to others, or a bypassed signal even.
-the tremolo thing you describe to me doesn't really sound like a problem per se - more like an artifact of massive gain with almost no signal, but I could be very wrong.

Debugging stuff like this is a bit like cooking dinner through the mailbox. You have the thing in your hands, you have to root out the problem, all we can do is make suggestions.
Once you've eliminated all the common parts as a possible cause, remeasure voltages for good measure and start off with an audio probe.

[Roger Martin]

Q4's E and B are suspicious. Can u change it with other transistor ?
What type do you use ?

[jozabroz2000]

Mike:
first of all, thanks for your time.
yes, i already made two with no problems at all. now made two more completely different builds and share no components and with this problem (same components-same stock)
yes, i tried without switch with no success
i will definitely try audio probe and see what is happening

Roger:
i did try other transistors than i am using now...2N5088 (original), 2N3904

it is very strange for me too
it looks like pcb problem, but I checked pcb, soldering, wires... million times
probably it is some stupid error which is not so obvious
very frustrating, but i will not give up!!!
if i find a problem, i will post it here for maybe future reference...who knows!

guys, thanks again

[jozabroz2000]

tested with audio probe...
getting a lot of noise in stage 3 (Q3)
not sure is it because of more gain (more transistors) or it is some problem
any suggestions?