CR-420 with left channel distortion

skidmarks70

New Member
So I've cleaned this guy and replaced all the capacitors in the power supply section. I thought I finally had it working and it sounded great on headphones.

I hooked up some speakers and it initially sounded good, but I've started to get an intermittent distortion only in the left channel. It's primarily in the bass and effects both A and B speakers. If I have either (or both) sets on I can hear it on the headphones. Turning off the speakers cleans up the headphones.

At first, cycling the power or changing the source would clear the problem for a while, but that seems to be getting less effective. I thought maybe it's a bad solder joint, so I reflowed the TR421-424 joints, but that didn't help.

mbz posted some transistor voltages in this post: http://audiokarma.org/forums/index....quested-with-next-steps.765622/#post-10465361

I'm going to check those next time I get a chance, but the pdf service manual I have doesn't list those? Anybody have suggestions for me?

Thanks!
 
Try cleaning you speaker selector switch. .. Maybe protect relay contacts...
 
I haven't tried cleaning the protection relay, so that'll be first on the list. I've cleaned all the other switches a couple times, so I'd be a little surprised if that was it. But, you know a lot more than I do so I'll give it a go!

Thanks
 
If I were a betting man... relay, but it might not be just the contacts. A bad cap or other part in the relay circuit can cause the relay to close with less manly vigor than needed. Check the coil voltage when the relay is closed.
 
If I were a betting man... relay, but it might not be just the contacts. A bad cap or other part in the relay circuit can cause the relay to close with less manly vigor than needed. Check the coil voltage when the relay is closed.
Yamaha's protect circuit is notorious for one or more bad caps in that circuit.Specially if they are violet sleeved.
 
At first, cycling the power or changing the source would clear the problem for a while, but that seems to be getting less effective.
Input Select switch may still have issues or bad solder connections.
 
Is there a trick to getting the cap off of the relay? I couldn't see how to get into it to clean anything. I haven't taken apart the selector switches, but did hose them down and cycle them a bunch. Seems unlikely that both switches would have the same issue in just the left channel.

The relay does have 4 violet sleeved caps nearby. I haven't checked to see what they're apart of. I may have some replacements for those.
 
Well, I tapped on the relay a bunch and now things are working. I think you guys have this figured. I'll check out that other thread later and see if I can't clean this thing up.

Thanks! You guys definitely know your stuff
 
I have similar issue with a cr 820 I just got. Distortion in right speaker. Very noticeable using aux and tape inputs, a little less with phono and hardly noticeable using tuner. Distortion goes away using headphones if both a and b speakers are turned off. The unit is very clean inside and I have cleaned the volume, balance, selector switches. I have also tried tapping the relay to no avail. Any suggestions?
 
I have similar issue with a cr 820 I just got. Distortion in right speaker. Very noticeable using aux and tape inputs, a little less with phono and hardly noticeable using tuner. Distortion goes away using headphones if both a and b speakers are turned off. The unit is very clean inside and I have cleaned the volume, balance, selector switches. I have also tried tapping the relay to no avail. Any suggestions?
Deoxit all your switches and controls first.
 
I have similar issue with a cr 820 I just got. Distortion in right speaker. Very noticeable using aux and tape inputs, a little less with phono and hardly noticeable using tuner. Distortion goes away using headphones if both a and b speakers are turned off. The unit is very clean inside and I have cleaned the volume, balance, selector switches. I have also tried tapping the relay to no avail. Any suggestions?

The noise came back on mine after a bit and tapping wasn't doing much. I still haven't gotten the cap off, but I reflowed all the solder connections on the relay and I haven't had a problem since. I think replacing or cleaning the relay is probably going to be necessary. I'm actually thinking about drilling a hole in the top of the cap and blasting it with Deoxit and then putting tape over the hole, since I don't have any scrap metal around to make shuckers. But I'm going to give it some time and see if it behaves first!
 
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