sizzling noise

Creighton

Member
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2,091
If a vintage amp makes a brief faint sizzling noise for about 5 seconds that fades out and then the amp has less headroom, I'm guessing that would probably be a failed electrolytic capacitor? Can a failed cap be identified visually?
 

zenas

Member
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8,759
Like a tube, (or a woman) a bad cap can look just like a good one.

Personally I don't mess with vintage electrolytics I replace them all.
 

Blue Strat

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30,183
What Zenas said, but a cap would be the last thing I'd suspect for the symptom reported. What amp is this? First thing I'd do is clean all tube pins and sockets and try again. Sometimes even simply removing and reinstalling all tubes can fix a situation like this. However, there are 50 other things that could be wrong. Start with the easy stuff and move on from there.
 

Creighton

Member
Messages
2,091
It is a '69 Ampeg G12 combo. All original except for tubes, speaker and three prong cable. I know the caps need to be replaced, I am just hesitant because I've had caps replaced in at least one other vintage amp which came back sounding worse not better. This one has sounded amazing till this issue and still sounds ok but something changed.
 

Blue Strat

Member
Messages
30,183
It is a '69 Ampeg G12 combo. All original except for tubes, speaker and three prong cable. I know the caps need to be replaced, I am just hesitant because I've had caps replaced in at least one other vintage amp which came back sounding worse not better.
That's a VERY rare situation unless caps other than the electrolyics were changed. If you have hazardous cap failure that takes either of the transformers I guarantee the amp will never sound the same and will lose significant value.

Anyway, start with what I suggested and progress from there. There's no way to pinpoint a problem as vague as this. You have to go through the standard troubleshooting procedure.
 

zenas

Member
Messages
8,759
I wouldn't even hesitate to replace every electrolytic in that amplifier. I've had all kinds of wierd noises go away with just that. And of course at the same time you're looking for bad connections and cleaning things. That always helps too.
 

slider313

Gold Supporting Member
Messages
8,223
The '69 GU-12 has its tubes mounted right to the pcb. I'm going to guess a power tube trace is heating up and lifting.
 




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