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Yamaha cr2020 trouble

OK, I did reflow the solder joints on the main pre board. It is working great today. So my next step would be to pull the cards and reflow the solder joints and clean off any flux. Thanks for your input! I may try to access the cards by pulling the switches back. Before, I pulled the amp heat sinks to get to them. Not much fun to work on this old beast. Ken
 
kenkirk said:
OK, I did reflow the solder joints on the main pre board. It is working great today. So my next step would be to pull the cards and reflow the solder joints and clean off any flux. Thanks for your input! I may try to access the cards by pulling the switches back. Before, I pulled the amp heat sinks to get to them. Not much fun to work on this old beast. Ken
Click to expand...
:thumbsup:
 
A possibility is that the switches are just corroded enough to play silly buggers; you exercised them a great deal in trying to diagnose the fault and this “cleaned” the dodgy contact in question just enough to make it work again.

In time the switch issue manifested again and hence you are back to where you were before?

I lost channels in both my CR2020s and only found them permanent again after unsoldering the switches, taking them apart and cleaning the contacts with brass wool.

I tried scrubbing with deoxit and a toothbrush before the brass wool
And it wouldn’t touch the tarnish on the contacts.

Again, just a thought and a bugger to implement for sure.
 
Yes the problem returned. I think my next step is to pull the cards and check everything and reflow the solder. I am also tempted the switch card A and B and see if the problem moves to the left channel. Then if none of this exposes the trouble, I will need to work on the switches. Yamaha really made it hard to work on this preamp.
 
kenkirk said:
Yes the problem returned. I think my next step is to pull the cards and check everything and reflow the solder. I am also tempted the switch card A and B and see if the problem moves to the left channel. Then if none of this exposes the trouble, I will need to work on the switches. Yamaha really made it hard to work on this preamp.
Click to expand...
Yup, take the chassis apart is my considered opinion after doing two of them...


DF518665-D8AA-4440-8B1B-2D14943E1EDC.jpeg

I chronicled the psychological side of redoing a CR-2020 on this thread: https://audiokarma.org/forums/index.php?threads/mid-restoration-regrets.982931/page-2 :D
The switched get a hard black tarnish on the contacts which soaking in deoxit doesn't seem to touch.
 
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