Need some help with The Thunderchief

[Fernando Aguirre]

Hi!

I have finished the thunderchief project from runoffgroove and i used j201 fets.
I adjusted the trims to correct values but i find that one of the trims can´t go lower than 8.3v. I tested the trim and it works ok, can it be a defective fet? any advice?
Thanks in advance.
Fer

[Brian Marshall]

what is the supply voltage?? sounds like the source of the fet isnt seeing voltage

brian

[Fernando Aguirre]

The supply is a 9v battery and the fet is receiving it.
I don´t know what it can be.

[Ed G.]

http://www.diystompboxes.com/sboxforum/viewtopic.php?t=20380&highlight=bias+thunderchief

[Brian Marshall]

what is the voltage on the source???


that other link looks interesting... i havent built one yet though.

[RDV]

From Gary @ R.O.G.

Remember that jfets are highly variable. You may find some that will not bias correctly, even though it is a J201 from the same lot. Always buy more than you need and sort until you find ones that will work.
_________________
Gary

Regards

RDV

[B Tremblay]

Along with the trimmers, sockets are highly recommended for this reason.

Are you certain that the respective trimmer is wired correctly?  Is there any voltage fluctuation at the drain of the FET while turning the trimmer?

[Fernando Aguirre]

Problem solved, i found i made a mistake with the value of a resistance and put a wrong one.
Now it is working properly and the fets are correctly biased.
It sounds really nice! it is lacking some gain but i think it is because of the battery.
Very nice and warm sound, very very Tube like.
Thanks
Fer