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.
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?
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.
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?
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.
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.