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Yamaha cr-420 problems

M

mondoman

New Member
I have a yamaha cr-420 that I have had for a few months. It sounds great...when both channels are working. The left channel on the stereo tends to go out. I have seen a few other articles on this site about this particular model receiver and DC offset. I checked the offset for my receiver and I am getting about 98 mv on the right channel and about 122 mv on the left. From what I have read on these forums I guess this is bad. I monitored the DC offset while the receiver is playing music and the left channel goes out when the voltage spikes up and i think the circuit protection circuitry is kicking in. I have already cleaned all the pots and switches with deoxit. I was wondering if anyone had some advice on how i can remedy this problem.
 
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mondoman said:
I have a yamaha cr-420 that I have had for a few months. It sounds great...when both channels are working. The left channel on the stereo tends to go out.
Click to expand...

Welcome to AK,

When the left channel tends to go out, do you hear the relay click?

If you don't hear the relay click, the protection circuit is not triggered. It may be only bad contacts. Clean the switches and pots with contact cleaner.

I had some problems with the contacts inside the realy, I replaced the relay.

For the offset, see my previous thread:

http://audiokarma.org/forums/showthread.php?t=155016
 
If you want to try setting the idle current first it is quite simple. The four output transistors when viewed from the front are TR423, TR421, TR424 and TR422. Directly in fron of TR423 is VR401 an adjusrtable resistor. Directly in front of TR421 are TP1 and TP2 a cople of test point pins. Adjust VR401 to get 20millivolts across TP1 and TP2.

Between TR424 abd TR422 is VR402 with a test point TP3 beside it and another TP4 in front a bit to the left. Same deal adjust VR402 for 20 millivolts between TP3 and TP4.

You do all this with volume controll at minimum and no signal input, simply select an input with no connection. You should find that the offset has been tamed some.
 
Hey Team.

Picked up my first Yamaha receiver the other day and absolutely love the design, look and feel of this thing, awesome. This CR-420 seemed like an easy "clean her up, plug in some speaker" type of receiver, but then the reality set in - there was a super loud, intermittent snap crackle pop happening out of only the left channel. I had cleaned all the pots and inspected everything and it all seemed to be working fine until I turned down the music and listened with the volume knob all the way down. It was then that I first heard the popping, wasn't loud, at that point, so I decided to give all the switches another cleaning - popping persisted. So then I started reading that it could be a contact in the protection relay, oxidation, etc. So I started wrenching on that thing, and man, what a pain trying to get that plastic cap off, such a struggle! Well, I got it off, and with all the wrestling I must have really messed it up because now it's not working, at all. Lesson learned, be gentle, take your time, find another way....

If I replace the relay and it still has issues I'm fine with trying to track them down, but I know replacing this piece will be critical if I want to move forward.

Anyhow, I'm keen to replace the thing now and wondering if I need to go with the exact match it had in it, which is labeled as FRL-264 DO24 02CK. I found one on ebay but it ships from Australia, so that's going to take some time. If there's an alternative that will work please let me know, and thanks in advance!
 
Man, that was fast! Thank you! Looks like the perfect fit and won't need to come from down under, whew, what a relief.

And thanks for the welcome as well. I'm finding my way one unit at a time, feels like I'm up to my knees so far, eager to go deeper! Dangerous for sure but I can't help it, this gear is way too much fun.

Thanks again @avionic
 
Could also be a solder connection or noisy transistor in the left channel power amplifier or pre-amplifier circuit.
 
Yes, you can hear it in the background. In the moments when the popping subsides the unit sounds clean and warm, but the violent popping a crackling just comes back, like in waves. Pots didn't seem too dirty to begin with but I was still surprised the noise continued after the cleaning. I'd also read about bad transistors, and that you could use the freeze spray to isolate them if the issue was happening as the unit got warmer - so I tried that too, seemed to make matters worse.
 
The solders look ok but I suppose I could refresh them? I have a multimeter so I suppose I could test each transistor, which I'm happy to do if you think that may be the cause.
 
Sounds like a plan, and yes, FM, with an antenna. I'll let you know how it goes, part has been ordered, excited to pop it in and continue the process. I sincerely appreciate your help!
 
Update: Looks like a mess but I got the old relay out, new one arrived Monday, appears to be the perfect fit.

Should I be concerned that the left side upper-most post hole is now missing the rectangular tin looking base that the others still maintain? Lastly, is there something I can safely clean this area up with? I used a solder sucker and desoldering copper braiding (neither were very impressive) to remove the old joints but it looks like hell to me.

IMG_5643.jpg

Thanks again for your assistance, here, excited to move on to installation and testing if I haven't totally ruined the board!
 
JB8 said:
Should I be concerned that the left side upper-most post hole is now missing the rectangular tin looking base that the others still maintain?
Click to expand...
Yes..... That silver piece was the solder pad for the relay coil connection.. Post a larger complete photo of the circuit board. so I can show you how to repair the missing portion.
 
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