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Yamaha CR-620 - Right Channel Popcorn Static

JB8

JB8

Well-Known Member
Acquired a CR-620, my first after a series of 400's and 420's, fun to get to know a new model!

This particular unit had a bad output transistor, blowing the main fuse, so I upgraded/replaced all 4 with MJ21193G's and MJ21194G's, which solved the problem, but now I have persisting popcorn static on the right channel once the relay kicks over. The static is present at no volume and across all functions, assuming it's a transistor in the power supply, would love some guidance on tracking down typical culprits.

I've tracked down bad transistors on 330c's and STA-78's by using freeze spray, should I just continue with that method or should I be testing voltages instead?

Thanks for the help, no hurry on this, enjoy the weekend.

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sruchris said:
Do you have any extra transistors? KSC1845? KSA992F? KSC2690AYS?
Click to expand...

Hey @sruchris , thanks for hopping in. I do have some 1845's but I don't think I have any of the other two, were you thinking do a quick swap out of most/all of the transistors now that the main outputs are new as well?
 
Thanks, both of you, much appreciated! I'm checking my supply for the 992's, and will swap if I have them. Specific to TR707/708, I noticed the 458's as well, but darn it, I must be going blind, where are 707 and 708 located? Feels like I've scoured the board a few times, they must be right in front of my face!

Thanks again, I'll get some transistors out, looking forward to tracking this down quickly if I have the parts, will keep you posted. :beerchug:
 
Thanks for the heads-up on 707/708, tough to get to but I did swap out 708 along with TR702/704 with the afore mentioned replacements, no change. Jiffy Pop should be ready soon... I can turn up the volume, left side sounds great, right sounds good once the volume is up but you can still hear the snap crackle pop in the background.

I did use the freeze spray, lightly, no change, no reaction from any of the transistors.

Thoughts on next steps?
 
Success! Replaced TR706 with an KSC1845 and the popcorn static has been eliminated, sweet!

I do, however, now have a very low level hum, 60 cycle perhaps. It's incredible low in volume but I'm not a fan. Plugged my headphones into a Hitachi running in the living room just to double check the hum, and there was none on the Hitachi whatsoever. I want complete silence if I can get it, ha!

Forgive me, I've not taken any time thus far to do any research on this but will take any advice on what might be the cause.

Lastly, thank you both for jumping, much appreciated as always!
 
Have you recapped the regulated and unregulated power supply ?
 
No Sir, not yet, I'll start doing some inventory of caps and see where I land.

Updates to follow, thanks again.
 
Gentlemen, to close out this thread, I'm more than happy with where this 620 has landed. After having replaced the output transistors, several transistors on the right channel, along with C802, 804, 806, 809 and 810, this thing sounds fantastic and the 60 cycle hum is nearly imperceivable.

I'm always facilitated with the personality of each unit based on the life it's lead - where it lived, who owned it, how they used it, etc., it all matters. This dude has exceptional stereo separation, a wonderfully Yamaha warmth, and now with all the new components it's chomping at the bit to sing. A completely sober evaluation, I might add, ha!

At any rate, cheers to you both, have a great holiday season, really appreciate the assist! :music:
 
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