Need Help Repairing AC Fried Fuzz Pedal

[ElectricDruid]

They're Wima film caps. Depending on the series and/or value, they'll be either polyester or polypropylene film. The numbers are the value, then the voltage rating. So:

3300 250 is 3300pF AKA 3n3, 250V max
0.01 630 is 0.01uF AKA 10n, 630V max
0.22 63 is 0.22uF AKA 220n, 63V max

They're good quality parts and available in very tight tolerances if required, but they're not cheap. They're available many places, but all the ones I know are European, so I'll let someone else step in. I'm sure Digikey or Mouser would have them though.

HTH,
Tom

[PRR]

> WIMA 3300 250-
> WIMA 0.01 630-
> WIMA 0.22 63-

"Film" caps. 3,300pFd (3.3nFd), 0.01uFd, 0.22uFd.

They only need to be 9V rated. However that may be too tiny to handle. Any higher rating will be fine if it fits the build.

Small Bear is one reliable source, and handles "only" the kinds of parts used in pedals. DigiKey Mouser et al carry tens of thousands of parts which mostly are not the best choice for pedals. (Too small, no legs, exotic specs for cellfone frequency work...)

[R.G.]

Thanks for the responses. I have already replaced all of the electrolytic caps, the regulators, and the diode. Other than the pots and switches, the only things left would be the resistors and non-electrolytic caps.

So does that mean you have already replaced the PT2399, or not?

I guess I should probably try replacing the remaining caps at this point and then the resistors thereafter if the problem persists. I am not familiar with these caps. Can anyone clarify what type of caps they are and maybe a good place to source them from? They read as follows:

It is unlikely that non-electo caps would have been killed by the AC. Although it's possible I guess.

It's most unlikely that the resistors would be damaged,

What about that PT2399?

[Govmnt_Lacky]

Going back to your power issue....

Since you are only getting 1.3VDC out of the regulator, you need to find out what is dragging the regulator output power down. I recommend removing the PT2399 IC and reading the output power at the regulator again. If it is still 1.3VDC then you will need to trace the circuit (find out where the regulator output power goes to in the circuit) and find out what is weighing down the regulator output.

Also... how exactly is this a fuzz pedal? Are you sure it isn't a delay-type pedal?

[bluebunny]

WIMA 3300 250-
WIMA 0.01 630-
WIMA 0.22 63-

These are film caps: 3n3, 10nF and 220nF (the second value is the voltage and is irrelevant in a pedal).  IMHO, putting WIMAs in a fuzz pedal is pointless.  A $0.01 ceramic would do fine, or just a regular poly film if you want to spend more than three cents.

Edit: everyone else answered already!  Who knew there was a page 2??    

[fenderguy81]

Thanks for all of the replies; I didn't even realize it went to a 2nd page until today. I looked around trying to find these film caps and found some on a site called Newark so I think I might end up ordering them there. The .01 630v cap is available in both a polyester and polypropylene. Is there a big difference between the two?

Also, the PT2399 was changed and I actually tried a couple other new ones as well that I had on hand, which didn't seem to make any difference.

Finally, I tried checking the reading with my multimeter on the regulator again with the PT2399 in the circuit and also out of the circuit. I got 1.3v on the regulator's 3rd pin and 1.3v on pin 1 of the PT2399 when the PT2399 is in. I got 2.5V on pin 3 of the regulator when the PT2399 is out.

Thanks guys!

[bluebunny]

The .01 630v cap is available in both a polyester and polypropylene. Is there a big difference between the two?

Price?    The first one is probably cheaper than the second.  In a glitching fuzz, don't spend more than you need to. 

Also, the PT2399 was changed and I actually tried a couple other new ones as well that I had on hand, which didn't seem to make any difference.

There's really no point in trying more PT2399s until you've got to the bottom of the regulator issue.  Though with so little on the board and with all those wide-open spaces, it's difficult to imagine you have a short or something similar?  I'm afraid I'm a little stumped...   

[Govmnt_Lacky]

Finally, I tried checking the reading with my multimeter on the regulator again with the PT2399 in the circuit and also out of the circuit. I got 1.3v on the regulator's 3rd pin and 1.3v on pin 1 of the PT2399 when the PT2399 is in. I got 2.5V on pin 3 of the regulator when the PT2399 is out.

You did read my previous reply... right?

IF you already replaced the regulator (which I believe you said you did) then you need to find out what is dragging down the output voltage (5VDC) from your regulator. Since you know it is not the PT2399, then you need to find out where the regulator output is going and find the culprit.

[fenderguy81]

You did read my previous reply... right?

IF you already replaced the regulator (which I believe you said you did) then you need to find out what is dragging down the output voltage (5VDC) from your regulator. Since you know it is not the PT2399, then you need to find out where the regulator output is going and find the culprit.
[/quote]

I am not sure how to figure out what is causing the voltage drag. I have replaced every component except the film caps and resistors so I am guessing it might be caused by one of the film caps. The 3rd pin of the regulator goes to an electrolytic cap then to a film cap. I am going to order the film caps and see if that helps.

[slacker]

You could try and find what it causing the voltage drop by powering the circuit up and then measuring the voltage on the different components, I would start with the electrolytic caps. If you find any that have 1.3 volts on then that means they're connected to the output of the regulator, once you've found one remove it and see if the voltage goes back up to 5 volts, if it does then that component was bad. If it doesn't then try and find another one, keep doing this and hopefully you'll find the problem.

[fenderguy81]

You could try and find what it causing the voltage drop by powering the circuit up and then measuring the voltage on the different components, I would start with the electrolytic caps. If you find any that have 1.3 volts on then that means they're connected to the output of the regulator, once you've found one remove it and see if the voltage goes back up to 5 volts, if it does then that component was bad. If it doesn't then try and find another one, keep doing this and hopefully you'll find the problem.

I traced 1.3v to one of the leads on C8 (100uf 25v electrolytic cap). I tested the voltage with it removed and got 2.3v on the 3rd leg of the regulator and 1.3v on pin 1 of the PT2399. I replaced C8 with another new electrolytic cap and everything came back down to 1.3v. I can't find 1.3v anywhere else on the board. Since everything else has already been replaced, other than the film caps and resistors, should I go ahead and order some film caps? If so, are there any brands I should avoid? I am going to order from Small Bear because the WIMA caps seem to only be available in the UK...I see Small Bear carries a .0033uf cap in a tropical fish mini cap. Would that be fine for this pedal?

Thanks!

[Rob Strand]

I traced 1.3v to one of the leads on C8 (100uf 25v electrolytic cap). I tested the voltage with it removed and got 2.3v on the 3rd leg of the regulator and 1.3v on pin 1 of the PT2399. I replaced C8 with another new electrolytic cap and everything came back down to 1.3v. I can't find 1.3v anywhere else on the board. Since everything else has already been replaced, other than the film caps and resistors, should I go ahead and order some film caps? If so, are there any brands I should avoid?

The regulator IC might be oscillating without C8 present which could be changing the measurements.  It might look like an improvement without it but that is not necessarily the case.

There's some resistors on the board near C8.   What is quite possible is the AC input has caused excessive current to flow and it might have fried a low-value resistor which is in series with the power rail (probably the + rail between the DC jack and the regulator).   I don't know if it has such a resistor but it would certainly cause trouble.

What you *really* need to do is trace the circuit from the DC jack through to the input of the LM78L05.  That will tell you what you are dealing with.   A slightly short-cut way to work out if there is a resistor in series with the +ve power rail on the input side is to measure the resistance from the DC jack +pin through to the LM78L05 input pin.   The measurement should be simple as there's no battery and hence no battery switching in the jacks to complicate things.   You then need to identify that resistor the PCB and read its value from the colors.  As a confirmation, using the multimeter, check one side of that resistor goes to the DC jack and the other to the LM78L05 input.   If the measurement and colors do not agree the resistor could be fried.

Next, you need to pull the *PT2399* out of the board then debug the 5V rail ie. the voltage on pin 1.   If you can't get 5V with the PT2399 pulled there's no point continuing.  Once you get 5V  I would put a resistor load from 5V to ground to see if the +5V voltage holds up with some decent load.   Start with say 10mA (470 ohm)  then go to 30 mA (whatever you have around 150, 180, 220 ohm).   You could try 50mA (100ohm) just to be sure.  Once you get that far you can be fairly sure the +5V power is good.   One caveat:  if there is a series resistor on the + rail of the DC input, high load currents will eventually cause a voltage drop across that resistor and then the input voltage to the +5V regulator will be too low and you will no longer get 5V.   If you can trace the circuit and know what the value of that series resistor is then you should have a good idea what current you can pull before that scenario occurs.