thunderchief doesn't bias at all

[mutant_guitar]

I recently perfed a thunderchief, and it does not work. at all. so, here i go...

battery: 8.86v

Q1,2,4
D: 8.64v
S: .55V
G: 0v


Q3
D: 8.64v
S: 5.16
G: .59v


i did not sub any parts, and i built the circuit exactly to the layout and schematic on ROG, at least, i'm pretty sure i did. i can't find any wrong connections so far.

it seems like none of the Jfets want to bias. at first i thought i had them all in backwards, so i switched 'em around, and that just made the reading around 7.8v at G,S, and D, so i switched 'em back. the 100k trimpots only cut off .2 volts.

i don't know why the 3rd Jfet is the only one that is different.

if anybody could help or point me in the right direction, i'd certainly appreciate it.

[rody82]

Had the same problem once.. i have wired the DC jack wrong... it took some time to realize that the GROUND WAS 9V too... 
After that, everything was fine.

Check that, and if its ok, then it should be wiring, soldering problem...

[davebungo]

It sounds to me like the trim-pots are adjusted to zero ohms!  Either that or you have made a mistake in wiring them up (like shorting the two ends together instead of the wiper to one other end)

[TryingToDo613]

I had the same thing on my Boogey pedal and I hadn't grounded two pot lugs that were supposed to be joined and grounded. I just had the jumper wire in, not the ground. Pedal still doesn't sound right. Always something. -ph

[mutant_guitar]

thanks for the input guys. i'll try all the things you guys have mentioned after i get home from school today.

[JimRayden]

Exactly the same problem as on my ROG Eighteen. And Fetzer. I had to go up to 1-2M to get it close to 4-5 volts.

Well yea, maybe I did have the Source connected to 9 volts... or something.

-----------
Jimbo

[RDV]

It actually sounds like you've wired the trims wrong. Are you sure they look like this?


RDV

[mutant_guitar]

it was the trimpots. i built the first "phase" of the circuit on another peice of perf, and i used the other circuit i just built for the layout. the only thing i did different was used radio shack trimpots. i tested it, and it biased perfectly. so, i don't know what will be easier, taking out the other trimpots, or building another circuit adding on to what i already did for testing. either way, i'll have it done. i just want to say thanks for all of the imput i got from you guys. this really is a great board, and i like it here.