Dr Boogey suddenly acting up..Help please

[rock_god_dan]

Hi, I've built electrictabs' Dr Boogey, and for a few months it was fine. But then it suddenly drops in volume. And when the volume drops, the sound becomes a little fizzy or fuzzy, I don't know, it lacks the punch it used to have. Then it goes alright again. Then the volume drops again. I don't know what's causing this. Could anyone help me? BTW, I'm running the Dr. Boogie at 12 volts to get that bigger sound. Could the jfets have gone bad? Or could the caps be the culprit? I don't really know how to test this. Please help.

[John Lyons]

Try replacing the FETs one by one. Hard to say what it could be...
If you hear some hiss when it's dropped volume it's probably not the latter/last FET(s)

john

[rock_god_dan]

thanks for the reply!  i replaced the last jfet with another j201, looks like i've fixed the problem. the volume's always low now haha! anyways, is it not ideal to run j201's at 12volts? They sound much fuller at 12v than when fed 9volts, but if it'll harm the jfets, i dunno... Anyway, my fets are biased to half or almost half of the supply voltage, standard Dr Boogie. Thanks for the help!

[John Lyons]

12v is fine for FETs. 18v is good as well.
If you still have low volume then how did you fix the problem by replacing the last FET?
Are the FETS in sockets? If so then try replacing them one by one and biasing them as you go.

John

[rock_god_dan]

It was just a placebo effect I guess. The problem's back, though not as often as before. I'm inclined to blame the volume pot. But seriously, I've been looking for threads with problems similar to mine, I haven't found anything. I don't know how to troubleshoot this 

Maybe if I audioprobed this? But then again the problem seldom happens now, I'm just afraid this might happen in the middle of a gig. Have you encountered problems similar to this? Thank you so much for your help.

Dan

[John Lyons]

Is the drop in volume all of a sudden like a bad connection?
Do you have an audio probe?
It could be the volume pot. Does the pot jump up an down if you wiggle the wires or knob?

Since it's getting fizzy when this happens I don't thing it's the volume.
How is the bias when it's no behaving? DId you check each transistor?
Have you replaced the transistors one by one?

So many questions...


John

[the recluse]

I had a similar problem and I finally had a chance to look under the hood and check it out today.  It seems that the root of my trouble was a bad transistor socket. I replaced the goofy one with a new better quality one and while I was at it replaced Q1 with an MPF102.  Played through it multiple times today for several minutes at a clip and all was well.  It's such a great sounding pedal.

[rock_god_dan]

Finally got it to work normally, but still under observation. It's only been a day so you never know

John:
You were right, it wasn't coming from the latter JFET's. I finally traced the problem to q3.

Recluse:
Damn, dude! You hit it right on. I totally overlooked the transistor sockets! I just looked for the loose sockets, adjusted the way the JFET was inserted and viola, problem solved! Hope the problem doesn't come back. This pedal is arguably the best non-tube distortion/overdrive pedal I have ever used. It really sounds and feels like a real amp, especially when cranked!

Thanks for the help guys, I appreciate it!