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Yamaha CR-420

J English

J English

Super Member
Just won a Yamaha CR-420 receiver on the 'bay...anyone have one? Any things to look out for? Last week I'd received an R-700 Yamaha but it turned out to be non-functional, all I was out was the shipping cost but it was still a bummer...it was in lovely cosmetic shape, but just not right inside. I am hoping the CR-420 will be better; at least the seller is representing it as 100% ok apart from a small ding in the cabinet veneer. I have a lot of smaller speaker options to throw at it, so the 25 WPC should not be a problem. Looking forward to trying out the "Yamaha sound" as opposed to vintage Harman Kardon, my main base of operations...
 
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CR-420 issues

The two issues that I ran up against were dirty pots (DeOxit got that out) and the concentric volume/balance controls tend to stick together (raise the volume, and the balance shifts to the right). Fortunately, the CR-420 has the variable loudness control (the only way to do it right), so you can use that instead.

They have a decent tuner, and sound more powerful than their ratings.
 
I remember that series liked to use a lot of mechanical grounds from copper on the PCB through screws to a chassis rail. If these ground connections get loose, all kinds of weird stuff can happen. To see if there's an intermittent connection, you can gently rap on the cover and see if you get any "spitting" type sounds.

If you find that you do have intermittent grounds, we used to like to solder extra grounds from the PCB ground locations to the chassis rail. We used fat solder braid. The metal won't like to take solder in it's galvanized state. We used to call it "Honda metal". Just scrape the area you want to solder with a razer or screwdriver. It will, then, allow you to solder to it.
 
jberger said:
The two issues that I ran up against were dirty pots (DeOxit got that out) and the concentric volume/balance controls tend to stick together (raise the volume, and the balance shifts to the right).
Click to expand...

For this issue, just pull out the volume knob, and then press the balance knob underneath it back in real hard, and then put the volume knob back. Problem solved! :)
 
J English said:
Just won a Yamaha CR-420 receiver on the 'bay...anyone have one?
Click to expand...

I owned the 420 and it is clean and detailed sounding more similar in sound to good modern gear, rather than overly smooth and muted sounding like some vintage receivers can be. You will be happy with it even if it is low powered, plus it looks stunning.
 
Thanks, everyone, for the good advice. I'll report back once I've fired it up. I am hoping it will get here today or tomorrow.

Pacific, the R-700 has a hot resistor, and my local tech, Bob, at Audio Labs Des Moines told me she was not worth fixing, as the power IC for this was no longer available, and that the hot resistor was probably a sign that the power IC was fried. (When I got her, sound was thin and patchy and then the resistor started to smoke.) Part of Bob's counsel I believe was that the R-700 was not a great Yamaha to begin with, and that even if we could track that IC, that something else was likely to blow. What are your thoughts? I did a little poking around here or at TapeHeads, and I saw that some limited ICs might still be around for it. Apart from the resistor issue, the inside is very clean and the exterior and cabinet are great. After seeing what you did with that Concept receiver...wow... I'm only $23 into this one, but I didn't want to just toss her, you know?
 
Avionic: I'm going to open her up tonight and see if I can get a proper identification of the ICs that might be involved, just to see if worth pursuing. How can I figure out what resistor I might need - it's a grey one that's smoking - anyone have a parts list for the 700?
 
J English said:
Avionic: I'm going to open her up tonight and see if I can get a proper identification of the ICs that might be involved, just to see if worth pursuing. How can I figure out what resistor I might need - it's a grey one that's smoking - anyone have a parts list for the 700?
Click to expand...

2 each STK1050II (power amps) and 1 each STK3056(voltage amp)
 
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I downloaded the schematics, avionic. I'm going to see if I can pinpoint that resistor. If I can figure out what path it's in, that may lead me to see if one or all of those ICs are the possible culprit. I looked up the ICs, they are available for pretty cheap. I haven't soldered or de-soldered in a long time, but might give this a try...
 
Hopping in on an old thread, apologies if this is not encouraged.

I have a 420 with a grounding issue, intermittent right channel loss. Tapping on the screw pointed out in picture #2, the channel pops back on. Slightly twisting the chassis will also induce the dropout.

Earlier in this thread is was suggested one could or should add new ground points to the chassis to solve the issue. I've backed out and retightened the screws but it didn't eliminate the issue.

I'm seeking advise on best next steps before whipping out the soldering iron and making a mess of a perfectly fine unit.

Any help would be much appreciated, thanks in advance!


YAMAHA CR-420 Ground (1).jpg YAMAHA CR-420 Ground (2).jpg
 
Thanks, @vinnysj, I cleaned up the screws/holes, did not install a washer yet. Still getting the cutout but I've also discovered I can get it to fail if I tap on the volume knob - which has also been cleaned with contact cleaner. The relay seems fine, no reaction by tapping on it. Also, when the right channel is silent in Stereo mod I can get signal to pass through it if I switch to Mono.

Still fiddling, thanks again for the advice, I'll let you know how it goes.
 
Ok @vinnysj, I think I fixed it. After tap tap tapping everywhere and getting random results I figured I'd get after the volume/balance pots again, and the loudness pot as well, seems to have done the trick. It's now been running for the last two hours, ish, and have had no cutouts. It dawned on me that I'd read in some post at some point that the loudness switch can be problematic for the stereo function, so giving it a second cleaning, and really getting after twisting the knob back and forth with intention, seems like it made the difference. We'll see!

Thanks again, I appreciate your help and this forum in general, quite the resource! :beerchug:
 
Just did a health check on my CR-420 because of a room rearrangement, alas am getting a substantial DC offset difference between the two channels (61mv left, 1 mv right, both values stable after 30 seconds). I have adjusted the idle current as per service manual to recommended values. Anything else I should look at that's simple versus caps replacement/rebuild? This one has given me 11 years of good service without issues, I can't complain...
 
I guess that your offset is negative on the left channel. If so, replace R407 by a 620 Ohm resistor. See this thread for more details

Yamaha CR-420 Offset: - 61mV by design!

First let me say I am a Yamaha lover, and I don't want to offend any other member of "the familly" by this title. Let me say also that I don't think there is any particular problem with an offset as low as this. A 60mV offset in a 3 Ohms load (typical DC resistance for a 4 Ohms speaker)...
audiokarma.org
 
J English said:
Just did a health check on my CR-420 because of a room rearrangement, alas am getting a substantial DC offset difference between the two channels (61mv left, 1 mv right, both values stable after 30 seconds). I have adjusted the idle current as per service manual to recommended values. Anything else I should look at that's simple versus caps replacement/rebuild? This one has given me 11 years of good service without issues, I can't complain...
Click to expand...
I had one as a kid in the 70's, great receiver.

I would say 61mV is nothing to worry about, just listen and enjoy.

Cheers
 
Yeah, somewhat zombie but tying up loose ends...

This thread is worth a read

Yamaha CR-420 Offset: - 61mV by design!

First let me say I am a Yamaha lover, and I don't want to offend any other member of "the familly" by this title. Let me say also that I don't think there is any particular problem with an offset as low as this. A 60mV offset in a 3 Ohms load (typical DC resistance for a 4 Ohms speaker)...
audiokarma.org
 
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