Non-working EHX Big Muff V2

[Kevin Mitchell]

No guitar signal should be in the power supply.

All over the board huh? How about the output jack?

[Gallagher90]

Almost all over the board

The white can cap just before the volume pot does not give any signal further on to the pot I noticed now.

Edit: And that cap also seems to give out 2.25v and the rest 0.xx or 0.00x..

[Kevin Mitchell]

If the signal is at the collector of the 4th transistor and not getting to the output I'd be inclined to think C2 (that can cap) is bad.

[Gallagher90]

I came to the same conclusion after a very good guidance on you part. Tanks!

So the white can cap is 1uF but what about the volt? what cap should I replace the original cap with?

[Kevin Mitchell]

Well first verify that the signal is at only one side of the cap. That would verify that it's a bad cap and not a bad solder/connection issue.

You can use any 1uF cap rated 10v or higher. You could even use a film or ceramic cap there instead if you'd like.

If the signal proves to pass through the cap and still not getting to the output jack, then check out the level pot and output wires. That'll certainly be the source of the problem.

[Gallagher90]

Already verified. The signal is clear just before and dead after the cap.

I have some caps on my Dr Q board that maybe can be used.

Theres a blue 10uF can (but thats to much uF right?).

And then there's a black can cap that says 15MFD 16v.

And then there's a green cap saying 100v .01+-10 (to low?)

here's a picture of the Dr Q board.

[Kevin Mitchell]

1uF is your safest bet. But if you want to experiment try em' out. See if it fixes the pedal but do not consider it "restored" at that point. Not until you get a new 1uF electrolytic cap there.

[Gallagher90]

Thanks for the advise but I think I'll play this safe and just get hold of a 1uf electrolytic cap.

As I understand you don't necessary get a better sound with a higher quality cap since the ''imperfections'' in lower quality caps can help form the sound as well. But do this specific cap has a lot to do with the overall sound of the pedal or does it affect the sound very little if you know?

[Kevin Mitchell]

Don't overthink on it lol. Consider that cap a safety part for the output and not anything tone shaping.

[Gallagher90]

I'll often overthink stuff.

Anyways I ordered 2 + 2 caps (always good with spares). 2 50v 1uF with copper legs good for audio stuff and 2 1uF 100v. I should get them next week then I'll do some soldering...

[Gallagher90]

Concerning the 1uF electrolytic cap does it flow both ways or is it constructed to take signal in one way and letting it out the other way? Noticed one leg is longer than the other on the pictures on the site where I ordered the caps.

[bluebunny]

Electrolytic caps are polarised.  Not only is one leg longer, but you'll notice a band with a line of negative symbols down one side.  The schematic will similarly show the polarity of the cap.  It's important that you get the polarity correct.  The worst case scenario is that it could explode.    If you have a film cap (or even a ceramic), then try this in the meantime.  It will definitely work and I doubt you'd notice any audible difference.

[Gallagher90]

Thanks for the input.

So does the signal go trough caps positive in/negative out or the other way around?

Edit: I'll probably will se on the old cap which way it should sit if there's a marking.

[thermionix]

Edit: I'll probably will se on the old cap which way it should sit if there's a marking.

Yes, and the PCB will likely be marked for the + leg.  The polarity relates to the DC voltages around the cap, not the (AC) signal flow.

[bluebunny]

So does the signal go trough caps positive in/negative out or the other way around?

You're misunderstanding the point of the negative and positive sides of an electrolytic capacitor.  It has nothing to do with the "direction" the signal goes (the signal is AC, anyway, as therm says: electrons are being alternately sucked and blown many times a second...).  It's all to do with the physical structure of this particular kind of capacitor: it has to be the right way round or you risk it exploding.  Film and ceramic caps - which aren't polarised - don't have this restriction and can go either way round: their structure is symmetrical.

[bluebunny]

Edit: I'll probably will se on the old cap which way it should sit if there's a marking.

You may find that the pad for the positive lead (long lead) is square.

[Gallagher90]

And why not a picture of the actual outside of the pedal. Pretty good shape. minimal rust.

[Gallagher90]

So I got my replacement caps today. Unfortunately I'm not at home at the moment but maybe I'll have some time after work during Thursday or Friday to go home and replace the cap so I can try the pedal out!

Some pictures of the caps.

[Gallagher90]

So now I finally got the new can-cap soldered onto the board but now the sustain pot has stopped to transmitting the signal so I can only hear the signal on the first part of the board once again. Have tried flicking the ON/OFF switch back and forth and even tried some contact spray on the pots.

Maybe I'll have to disassemble the sustain pot and give it a deep cleaning...

[Gallagher90]

So I cleaned the sustain pot which wasn't that dirty and then I started thinking that the fault is not with the sustain pot.

The signal goes from the input all the way down to the first transistor and then onwards to the sustain pot and from the pot to the rest of the board right? Now I don't get the signal past the first transistor and therefore the sustain pot gets no signal to distribute further.

Or am I understanding the signal flow incorrectly?