Blues DeVille reissue squealling preamp

[Jazz P Bass]

Got the Blues Deville

Well I checked that coup. cap in circuit for dc and found none(I know thats not the right way)

That IS the way to check for Vdc leakage.
In circuit.
You could always bypass the whole tone control to rule it out.

[terrykvan]

Which Gerald Weber book had the cap probe. The title is "Tube Amp Talk for the Guitarist and Tech" I enjoyed reading it. The cap probe is my idea based upon His suggestions for fixing hi freq oscillations.

Oh, cool, thanks

[terrykvan]

Oh, sorry, I had read that you had to lift the grid side. I did'nt know why. I guess if there's no DC then everything's cool anyway. Then if there is you have to make sure of the source. I can actually tweek the tone controls to dial out the feedback and get the gain on up to about 12:00 which is plenty nasty enough for me but not fixed. When I say "dial out" I don't mean just turn the treble down, but flatten the response. If I turn the treble down, I get a lower pitched feedback and so forth. So a nice good sounding setting is what the amp likes. I would be afraid to bypass the tone section altogether. Some of those components have to be there, like the 250pf cap. And wouldn't the extra gain(especially treble) wreck havok? Just guessing.

[Jerry]

I recently worked on a Fender Blues Jr. that had an oscillation problem. It ended up being the filter cap for that part of the amp.

[terrykvan]

BINGO!!! Thanks a ton Jerry. And to all others for their help. Feelin kinda stupid for not ckecking that sooner.

[frankeg]

I recently worked on a Fender Blues Jr. that had an oscillation problem. It ended up being the filter cap for that part of the amp.

Way to go Jerry. I do enjoy happy endings.....

[John G]

Hi,
Not the Deville , but the Deluxe.
John

[booj]

my guess is a bad filter cap at that stage

[terrykvan]

Thanks, appreciate that. I eventually found that same service man. for the Deville but I will add it to the library and pay it forward.

[terrykvan]

You're correct, got it fixed this mourning with a tip from Jerry. Guess I had a leaker. Since the clean channel sounded so good, loud and noise free I never suspected that.