Dr. Boogey works... for a little while...

[madboy]

Hey folks. Just finished the Dr. Boogey, and after removing one little solder bridge, it works... for about 2 minutes... then farts out and fades away. The Q1 drain is set for half supply (about 4.75 volts ), but then mysteriously floats up to 8.95 volts ( the source is a 9.5 volt ). I've tried a couple of different J201s, with the same result. I'm still fairly new at this ( still a solder-by-numbers guy ), and thought maybe someone out there could shed some light on the situation. Is there something I'm missing? Thanks in advance for your help.

[WLTerry]

Check again all your solder points, sometimes they became cold solder, that happens to me when I built the EA Tremolo in the trimmer, because the need of tweak it maybe the solder went bad. So check the Trim1 first.

[madboy]

Hmm... I tried what you said... actually touched up all the joints. All the other fets are fine and stable, it's just Q1 that is drifting. Is it possible I got a bad trim pot? A bad cap? Anyone? ( 'cause for the few minutes it's working, it sounds great! I'd love to get this one boxed up!)

[the recluse]

I am having a similar issue, but haven't had too much time to investigate.  I will be taking a look at it in the next few weeks (I hope).

[WLTerry]

It's probably a bad trim pot. Replace the Q1 trimmer and then check if the drain voltage is in the right value.

[miqbal]

........or with a fixed resistor.

[ambulancevoice]

........or with a fixed resistor.

nope, a trimmer is needed to set the bias of the fet just right

[miqbal]

........or with a fixed resistor.

nope, a trimmer is needed to set the bias of the fet just right

Trimmer is only a variable resistor. You can always replace it by one, two, or more resistor once you get the preferred value.