Finished wiring a second Dr. Boogey...

[Connoisseur of Distortion]

and hell if it isn't pissing me off.

it worked as soon as i trimmed, and the sounds coming out are good. I don't even mind oscillation all that much; when i hear a whine in between palm mutes, i draw the line.

I used the wiring configuration that grounds the effects input while bypassed. Strangely, it oscillates (albeit quietly) while bypassed. I also noted that it oscillates when my guitar volume is turned off, so i believe the problem is in a later section of the circuit, that the switch is doing its best.

While trimming, i could not get the voltage low enough on one trimmer (stayed about a volt too high). All trimmers worked fine except for the last one, which stayed high.

If anyone has advice about the mystery noise, please post. I'll update this as i work through it.

[MartyMart]

Yup, "Jfet" trimming to 1/2 V ( or whatever ) can be a P.I.T.A  !!
Often best to try some more Jfet's in that "position" , than hammering on
one to try and bias it !
The most "miniscule" hair of copper/solder will screw you every time, make 100%
sure that the "Jfet socket/pads" are all perfect ....
Cheap "one turn" 100k trimmers can be sometimes difficult, like you get 3.2v then 1/2 mm
later ...... 8.3 v   !!

Marty.

[petemoore]

  Is there any difference in layout between DB#1 and DB#2?
 

[Connoisseur of Distortion]

thanks for the replies!

Marty-

I know what you mean. i'll try some more J201s, and maybe one will bias in like it should. does this seem like a plausible cause of the oscillation? And yeah, i'm using those wacky one turn trimpots that jump around insanely. they're so obnoxious, but once they're set i just don't care...

Pete-

Funny thing. I used the same layout, but my last Dr. Boogey was not sized properly. it was MASSIVE, the board almost touched across the 1590BB it was housed in. It had some problems as well, but the oscillation didn't tend to interrupt like it is doing now...


Like i said before, the circuit feedbacks even while facing a low input impedance (like my guitar turned off) so the problem is probably later in the circuit. Also, the gain pot cannot entirely stop the oscillation; turning it off only changes the tone of the noise.