debugging prof. tweed

[donald stringer]

I have the circuit built, and have checked it numerous times but still can not get it to function. The symptoms are/guitar signals passes through but uneffected. The trimmers on the first and third mpf 102 have to be turned all the way counter clock wise for the signal to pass. The trimmer on the second 102 has no effect. The code on those radio shack trim pots, is the 104 an 100k and the 103 an 10k or vise versa, I might have the wrong trimmers in. Second, is that an 470 ohm or 470 kon the third  102 [source]/ and last but not least I want to make sure I have the right size caps in, 4n7=.0047, 22n=.022, 2n2=.0022 If any body else has had any problems with this circuit I would appreciate the feedback. I want to get back in the hang of building these things,my j-fets are gonna be here in a few days.

[petemoore]

Them source/emitter resistors used to get me.
 Generally they're small, without looking at the schematic I'd say 470 ohm. Schematic link? what did it say exactly there ... "470" is 470 ohm/
 104 marking on trimpot is 100k
 103 is 10k
 measure the resistance on outside lugs with DMM to see precisely what the resistance is, I use some trims with no readable markings .
 Probably a bias issue, you can measure the voltage of all transistor pins S,G, and Drain from ground,...this will tell you where the biasing issue is.
 Reads at GEO tell 'what's on and off' about biasing voltages of Jfets, or post the readings here.

[Lonestarjohnny]

I've built 2 and have had no problem with them, If you don't have a DVM to test those pot's with it would be a good idea to invest in one, for checking those pot. values and setting the Bais on your Jfet's, if you use 100 k pot's you'll have no problem getting them to bias,
and that's a 470 ohm resistor on the source of Q-3.
JD

[donald stringer]

After I stared at the circuit for three hours saying to myself I just dont know whats wrong. This circuit was built exactly according to specs. Then my eyes focused on the second trimmer[it ended up that it was not soldered to q2. After that the circuit itself works fine, the only but is the tone control does not have as much an effect on it as I would think it should .Is it supposed to be as subtle as that.I am going to have be more careful nexttime on soldering, when ever I get in a hurry I am apt to not follow through and miss a certain portion. I think this circuit is going to sound great when I am done, it has a nice od to it that I havent been able to get with certain other pedals.