CRATE BV amp Ch1 prob- "Crunchy" Noises.

[Sea Chief]

If you will, please ground , one at a time, both sides of C20.

Done:
R34 side to gnd = noise ceases.
R35 side to gnd = noise remains.

[Sea Chief]

Does this suggest a dodgy (ceramic) C20 maybe??

[Jazz P Bass]

Do you have a replacement cap for C20?
For now, anything even close would do.
Not too sure why they spec'd a ceramic disc cap there.

[Sea Chief]

Yes I do have a 102 ceramic on an old unused Fuzz Face board I could whip out. tho its about 1/4 the size, the legs are spaced same & I could just squeeze it in I think.

Have I ruled out R34? or is it worth replacing that at same time, or not the thing in Q here-?

[g1]

I think you can just jumper across C20 for testing purposes as there is no DC present here.
No, R34 has not been ruled out. But Q5,Q6, D4 and D5 have been ruled out.

[Sea Chief]

Changed C20.. noise still there. Godammit. This thing is -the- biggest pig to undo board/ replace.

Ok so if Q5,Q6, the 2 diodes, and now C20 can be ruled out.. does that mean it simply -has to be- one of the other few components left between C19 and MV?

[g1]

Ok so if Q5,Q6, the 2 diodes, and now C20 can be ruled out.. does that mean it simply -has to be- one of the other few components left between C19 and MV?

That is my feeling. And though I won't rule them out, I'm less suspicious of the controls as moving them didn't seem to affect the noise.
Try your shorting jumper ACROSS the following components, one at a time: R34, C21, C22.

[Sea Chief]

Try your shorting jumper ACROSS the following components, one at a time: R34, C21, C22.

Done: shorted across each R34, C21, C22... noise remains.

[Jazz P Bass]

Is this something new?
C20, R34 side grounded : noise ceases.
R35 side no change.
But, R38 grounded noise ceases.
Now I am confused.
Further back from C20 is C17 & R26.
SC, can you find the point between these two components & ground it?

[Sea Chief]

Is this something new?
C20, R34 side grounded : noise ceases.
R35 side no change.?

Yes, this was where I thought I might be zero'ing in finally on the prob this afternoon.

But, R38 grounded noise ceases.
Now I am confused.
Further bach from C20 is C17 & R26.
SC, can you find the point between these two components & ground it?

Done: grounded @point between C17 & R26... noise is here/ remains.

[g1]

Is this something new?
C20, R34 side grounded : noise ceases.
R35 side no change.

This seems to be a pretty key item. Could you please double check, and make sure which side kills the noise.

[Jazz P Bass]

Wells folks, that leaves C19 & R33.
There won't be any grounding tests on these two parts.
One at a time, I would change them out.
Any value close will do for a test.

[Sea Chief]

This seems to be a pretty key item. Could you please double check, and make sure which side kills the noise.

Actually I did just that in case I was going mad..

C20, R34 side: noise ceases. Definitely/ 100% sure.

[Sea Chief]

Wells folks, that leaves C19 & R33.
There won't be any grounding tests on these two parts.
One at a time, I would change them out.
Any value close will do for a test.

Ok I will change these out tmrw. Its a procedure & a half. Ones a spanking looking red wima. t'others a spanking looking 221k. hmmm. Ill report back tmrw.

cheers alot JazzP.

[Sea Chief]

Wells folks, that leaves C19 & R33.
There won't be any grounding tests on these two parts.
One at a time, I would change them out.
Any value close will do for a test.

Done C19 and R33.. noise remains. chrissakes!