Ancient capacitors - glued or blown?

[Coolin]

Okay, I have this old hifi amp with virtually no output. Two big capacitors sit in solidified brown puddles.



No other capacitors on the board look like this. Can anyone please tell me if the brown stuff an adhesive, or has something leaked?

Thank you!

[selldoor]

Re: Ancient capacitors - glued or blown?

Big Amps often have the caps glued in position - by the way it is flowed up the sides I reckon it is glue.

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[ben7]

Re: Ancient capacitors - glued or blown?

Yes, it is just glue. Adding to what selldoor said, the glue is to hold them in place - so they won't jiggle around, crack solder joints, or rattle on something.

Is the sound distorted, and quiet?

It could be a number of things, a bad resistor, bad transistor, or a dirty volume potentiometer (or a dirty switch too).

[jetadm123]

Re: Ancient capacitors - glued or blown?

Definitely glue. Stuff turns rock solid over time and will take time and patience to get off. Looks like the glue on the right cap is alrady cracking. You can try heating each lead of the cap and rocking the heated end to break that adhesive bond. If the glue is still somewhat soft, try using a sharp knife to score around the cap before you try removing it.

[theOracle]

Re: Ancient capacitors - glued or blown?

as someone who has restored 100's of old guitar amps and old stereo hifi amps, you definitely want to replace every single electrolytic "can" type cap in this entire amp - will likely fix the problem, and if nothing else, will vastly improve the sound and future reliability. Doing this will also protect the other hard to find components, such as rare transistors etc.

just stick with Rubycon, Panasonic, Chemicon, Nichicon or Suncon (Sanyo) and stick with suppliers like DigiKey, Mouser, Newark

use same values and you can go up in voltage if you like


when caps get this old, they die, or at least get way out of spec, from old age, not from leaking, manufacturing defect, etc.

so replace them no matter how perfect they look!