Leaking capacitors?

daccordimark

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I've just taken temporary custody of a Rotel RQ-970BX phono stage and knowing the real owner is a keen tweaker I opened it up to see if he had breathed on it at all.
As it happens it's not been touched but I was slightly alarmed to see trails of brown gunk that seem to come from some of the capacitors.
Have they been leaking at some point? I should point out this hasn't been powered up for years.



IMG_20220731_174450754.jpg
 

audio_PHIL_e

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I'd recommend replacing all them electrolytics before powering that up. Even the little ones that look as if they are still intact are the same age as the big ones and are probably about to spring a leak sometime.
 

Beobloke

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The brown gunk is adhesive used to secure the capacitors to the PCB to minimise vibration. However, this is bad news. Over the years this stuff goes conductive as it ages and so may well start shorting PCB tracks out. It’s final party trick is to then go corrosive and eat away at said tracks. Personally I’d get it all off as soon as you can. It’s not a trivial job as it involves removing the capacitors and then persuading the stuff itself to part company with the PCB without damaging it.

The capacitors themselves are very good quality ones - they are showing no sign of bulging and so will be fine - don’t worry about them.
 

Strider

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Nowt but good old hot melt glue to hold the caps in place. - Back in the day it was some sort of resin before the glue became the norm.
 
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daccordimark

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Thanks for all the replies, (well almost all @Warszawa - fo.q tape indeed!). I'll have a word with the owner and see if he wants me to investigate further. No harm in removing the board and checking the underside in the meantime though.
 

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