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Technics SU-7700 relay wrinkle.

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oldnotbold

Member
Have just finished trying to find the source of poor reproduction from a Technics SU-7700 - all the usual gremlins, crackles, pops, channel drop-outs etc., and de-Oxiting all pots and (accessible) switches made no difference, so I did what I should have done much earlier - tapped the relay.
Clearly the culprit, so out it came for contact cleaning. The after-checks with a multimeter were discouraging, to say the least. On close examination, the contacts were unlike any I have seen before. Instead of being flat, they were a very dirty 'hill and a dimple', so that cleaning both resulted in a clean top of the hill by-passing the clean edge of the dimple and going down into the still dirty hollow. Does all that make sense?
Anyway, careful scraping with a curved dental scraper into the dimple solved the problem and I now have a fully functional SU-7700.
Just thought I'd share that with you...
 
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I would suggest that you have done a great job sniffing out the problem but will only have a temporary solution.

Long term you should replace the relay, once the hard contact plating is gone or damaged like you described it is just a matter of time before it gets crappy again. Might be a good long time or might not?
 
Don't know the part #
Many new relays still available for many units.
Oftentimes, if not, a new can be modded to fit existing
 
Oh, wow and Oh, woe! Thought I was being such a smart-ass with my efforts, but it seems both mrk229 and nj phoenix have done that, been there and got the T-shirt.
I had no idea that, given the architecture, the hard coating existed and would ultimately decay, so thanks a bunch, pals!
Seriously, what you both say makes perfect sense, but as in a few days time I will commence my seventy-eighth orbit around the sun I am hoping that my efforts may well prove to outlast me.
In the meantime, many thanks for the responses. It is really comforting to know that such a band of enthusiasts exist to help and share experiences and knowledge in this 'Me First!' world.
 
Congrats on the 78th orbit. :beerchug: I'm a few rotations behind. ;)

That fix may outlast both of us.
 
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