Crimso Elektrik 530 Amps with hum - repair / restauration?

Hi there everybody!


I have a pair of vintage Crimson Elektrik 530 mono power amps.

They worked and sounded pretty good. However, they started humming some time ago, and its getting stronger over time, in particular on one of both. Otherwise they still work well, but given that I have high-DB-speakers, the humming got really disturbing.

I have no clue in electronics... but I am ready to exchanging parts, soldering on the board, etc. So I just would have to know, what to do...

More precisly, my question to you guys would be:
- What should be done to troubleshoot that humming?
- Are there parts that should be exchanged anyways for their age? What parts (brand/type) would you recommend for the replacement?
- Might I start with re-soldering together the old parts in order to improve contacts?
- Honestly, would you think, taht it's worth the time and cost, or should I rather look out for something new? Given that soldering and parts shopping is not exactly my hobby. but I do it if this gets me back my nice amps.
- And if I already start soldering... are there upgrades that would make sense?

Below you find the pictures of the board and parts inside the amps...

Thanks INDEED!!! for any useful help and advise!!!

Best regards, Urs


Link to pics: Crimson 530 — ImgBB
 
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That looks like a nice unmolested example. There is something odd on the heatsink side of Tr15. Is that a toasted Ceramic capacitor or just a wodge of dust?? Prob not the cause of the hum. The variable resistors do deteriorate with time and are probably best replaced with multi turn equivalents which necessitates resetting the biasing. That is something for a specialist on these amps.

Anyway I agree with latata. That'll be the best way of getting them re-capped and set up again. The output stages of these were prone to instability into tricky loads and Brian is the expert.

John