Squealing 5E3

[pbiagi]

Hello,

My first 5E3 was working fine and sounding fantastic for a good while (over a year?) but recently it started having these symptoms (in this order):
- sometimes the volume would go way down, and the notes would be strangely distorted. This usually occurred when playing low notes on the guitar. Sometimes it would just go away, or turn it off and come back later and it'd be fine.
- loud crackling noises - could occur by themselves (or seem to), or when moving guitar chord, or playing a little louder (on the strings).
- very loud squeal. We live in a small apt. .. so this is making testing difficult. Placing the amp face down helps a little.

It goes into the oscillation - weeks ago lost power and distortion, now loud crack and squeal - always after a few minutes, I'd say 3-6 min. First couple min., no problem.

I've tried:
- pulling the 12AY7 tube - no noise. However it seems the amp needs some input to get the oscillation started (I assume).
- replaced 12AY7 tube. Same issue.
- verified grids on 12AY7 and 12AX7, jack connections.. everything seems ok. Resoldered a suspect connection, but still same issue.
- reset the tube socket pins..

Have a gig Friday and would love to use this amp.
Appreciate your guidance.
Paul

[pdf64]

'It goes into the oscillation - weeks ago lost power and distortion, now loud crack and squeal - always after a few minutes, I'd say 3-6 min. First couple min., no problem.'
Possibly a bad power supply cap - have you got spares you could sub in?Pete.

[pbiagi]

Thanks Pete.
Is it the first power supply cap? or all 3?
I have spares to replace all 3 if needed, and will try this tonight.
Paul

[pdf64]

Paul, it could be all, any or none; maybe the cap is ok but the ground connection to them bad somehow.
From your symptoms, I'd confirm the second cap, on the screen node, first. Pete

[pbiagi]

Small quick update - didn't have much time last night to work on the amp.
After redressing the grid and plate wires, a few others, I get no sound at all.
Tried changing out the 12AY7 a couple times, no sound.
All connections seem OK but there must be one broken.
Tonight I will try resoldering all connections and possibly changing out power supply filter caps - they seem ok.

[riz]

Take it as a good thing that you're getting no sound now, that SEEMS to confirm just a bad connection. Solid core wire? Gig tomorrow nite, sounds like someone needs to MAKE some time!! Good luck!

[pbiagi]

Thanks for the moral support. Yes it just took a little time to locate a loose ground on the 12AX7 cathode..
Yes I got to use it for the gig - sounded great.
best, Paul