CR-420 right channel issues

J

JPromo

New Member
I love my 1020, so I picked this up recently for a second receiver. Fully tested upon getting home and the right channel only output distortion, not even distorted music, just buzzes to the beat.

Thorough de-oxit didn't fix it. Needs caps, but I wouldn't think caps would cause that dramatic of a distortion.

Output transistors tested no shorts. Then I was checking voltages on the OTs and.. slipped, shorting one left channel momentarily. Suddenly both channels came in clear. It played perfectly for maybe 10 minutes, then quickly degraded back to where it was with the right channel distorted.

So, what could this be? I'm familiar with the grounding issues on these CRs, so I will start there, but any other thoughts? Thanks!
 
JPromo said:
. Suddenly both channels came in clear. It played perfectly for maybe 10 minutes, then quickly degraded back to where it was with the right channel distorted.
Click to expand...
Possibly cold solder connection somewhere on that amplifier assembly.

PS get yourself some mini-grabber test leads. To minimize test point slippage and burnt up components.
 
Tap on the protect relay and listen for audible changes to the effected channels.
 
avionic said:
PS get yourself some mini-grabber test leads. To minimize test point slippage and burnt up components.
Click to expand...

Amen. I just get excited when I get a chance to tinker on something.

On the other hand, the fact that it jolted itself into working temporary eliminates some possibilities.. I will check for cold solder when I get under the board.
 
Next time the channel cut out, I knocked the relay a few times and my right channel came back. Any special way to clean it? The lid looks like it can be popped off.

Thanks for the suggestion, avionic!
 
JPromo said:
Next time the channel cut out, I knocked the relay a few times and my right channel came back. Any special way to clean it? The lid looks like it can be popped off.

Thanks for the suggestion, avionic!
Click to expand...
Replacement is prefered remedy.
 
Fujitsu FRL-264 d024/02ck

Seems that's 24v. Would your linked relay be suitable, or would it be best to track down an NOS one? I'm already putting a mouser order together, so that would be great if it would work. The footprint looks right. Thanks again for the help.
 
I have the same issue on my 420.....channels cut in and out when tapping on the relay. However, on mine , it does the same thing when using headphones. Does this rule out the relay as the problem?
 
Chaulk61 said:
I have the same issue on my 420.....channels cut in and out when tapping on the relay. However, on mine , it does the same thing when using headphones. Does this rule out the relay as the problem?
Click to expand...
Nope...
 
Look at the schematic. You will see that the headphones and speakers binding posts are both after the relay.
 
Replacement is always the best solution, but if you need a temporary fix, soak some thick paper in Deoxit and drag it through the contacts of the relay. You'll be surprised how much gunk comes off. The problem is that the contacts become pitted and dirty after time. The dirt can be cleaned, but the pits need to be sanded down - better to replace at that point.
 
Theres always the remote chance of a bad solder connection on the relay or in close proximity to the relay.
 
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