Strange (to me) Cherrybomb problem

[daverik]

Greetings all,

Just completed my Cherrybomb build and am having  a strange problem.  When I power the pedal on all is fine and it sounds great, for about 5 - 10 seconds.  Then it goes into the fuzzy / fizzy / distorted mode I think I've read about on these boards.  I've changed transistors, no difference.  Here are some specifics on the pedal, maybe someone can point me in a direction.  I've already re-flowed all the solder joints (3) times so I don't think it's that.

Input voltage at battery - 8.8v (tried another battery at 9.6v, no change).
I used an electrolytic cap for C-1 with the minus side to output (tried the other way, no change).
I used a 4-position switch for the gain control with 33k, 50k, 81k and 1k resistors on the outputs (tried removing this and using a 5k trimpot, no change).
Transistors - Q1 and Q2 - 2n2222, Q3 - 2n3904 (tried Q1 and Q3 - 2n3904, Q2 - 2n2222, no change).

Voltage at the transistors are:

Q1

C - 1.38
B - .30
E - .06

Q2

C - .80
B - 1.37
E - .73

Q3

C - 5.42
B - 1.5
E - .88

From scanning these boards it seems the only one in range is Q3.  Any ideas on where to look first (or second, or third...).  Thanks, Dave.

[Mike B.]

Well first, the Mangler uses PNP transistors not NPN and second, there is no Q3. Are you sure you aren't talking about a different circuit?

[daverik]

Wow... I really need coffee before I post.  This is a Cherrybomb, not a Mangler (that's what's on the bench now).  Thanks for the quick reply.

[Bret608]

If I remember correctly, C1 on the Cherrybomb is 220n. If you used an electro for this instead of a film cap, what value was it?

[Mike B.]

Yep, I think it's 220n as well. Pics of your board might be helpful at this point. The fact that it works for a few seconds seems to point to a capacitor issue, but not always.

[daverik]

Well, I took the .22 electrolytic out and put a film cap in, no change (actually, two .1 film caps wired in parallel).  I guess .22 electrolytic caps are not the norm,  usually this low they go to film, correct?  I have a ton of yellow .22 electrolytic caps from an old Thomas organ that I've been recycling. 

Since I made this change I have been away from the bench for a few days and have not had a chance to do any further testing.  I will take some photos and post them once I get back.  Thanks for all the assistance.  I've modded several pedals but this is my first "ground-up" build.  The way I look at it, I'm gaining valuable diagnostic skills.  Dave.