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Yamaha CR 620 with loud hum.....

red71rum

red71rum

Active Member
I got this receiver from an elder couple the day before yesterday. The receiver is in pristine condition, no scratches on the glass, the case is flawless, all the lights work, the relay clicks on etc. The problem I am having is that there is a very loud hum coming from both speakers. It sounded like a grounding problem from my limited knowledge. I tried plugging it into another outlet, switched out speakers wires and used ones from another receiver and so on. I cleaned out the speaker connections. I opened up the receiver and there is no dust in in. I cannot see any bulging caps, but then I am a computer tech and not an audio technician. I asked about this in a audio group on FB and some pointed to the main filter capacitors. Any opinions on what I need to do? I will have to find a tech as this is probably way beyond me. I have included some pictures of the CR 620.
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red71rum said:
some pointed to the main filter capacitors.
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That could also be the issue..The fact that it is humming in both channels. Points to a power supply issue.. This is the power supply section..
 
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avionic said:
View attachment 2144476


That could also be the issue..The fact that it is humming in both channels. Points to a power supply issue.. This is the power supply section..
Click to expand...

I found a tech in my area (techs are hard to find here) and am taking it tomorrow to find out. It will be interesting to see if it is the power supply. I will reply back tomorrow to the thread or as soon as I find out.
 
red71rum said:
I found a tech in my area (techs are hard to find here) and am taking it tomorrow to find out. It will be interesting to see if it is the power supply. I will reply back tomorrow to the thread or as soon as I find out.
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All the power supply caps can be suspect. Also mention to your tech to loosen, and re-tighten ALL of the board screws that are grounding screws too.
 
Skywatcher said:
All the power supply caps can be suspect. Also mention to your tech to loosen, and re-tighten ALL of the board screws that are grounding screws too.
Click to expand...

I also thought it might be a grounding issue, it almost reminded me of a turntable that was not grounded. There is a pop in the speakers when I shut the receiver down also I believe (I dont want to turn it on again to check until it is being looked at for fear of damaging it or my speakers).
 
Wiring looks a bit like spagetti. AC supply wires to lamps etc should twisted. Transformer secondary wires in close proximity
to main caps. Google CR620 for some internal pix and compare with your unit. You could try pushing some wires around with
something non-conductive(chop stick?) and see if it has any effect on hum.
 
avionic said:
Not if its popping.. Lamps are mis-wired. Could also be the source for your hum..
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Interesting, the owner did say his grandson opened it up and cleaned at one point, I wonder if he tried getting the lights going and messed up? I cannot be sure, but think he might have done the lights.
 
The tech I took it to had to clean a dirty resistor and relay, got it going for me. He called and also asked if I wanted to have him change the large caps. When I was there with him testing, they are rated 65000, they were half that when tested. I have to decide whether to leave them in and see if they reform, or have them replaced with some other capacitors. I don't know if it is worth having it recapped or not?
 
red71rum said:
The tech I took it to had to clean a dirty resistor and relay, got it going for me. He called and also asked if I wanted to have him change the large caps. When I was there with him testing, they are rated 65000, they were half that when tested. I have to decide whether to leave them in and see if they reform, or have them replaced with some other capacitors. I don't know if it is worth having it recapped or not?
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It is worth it I have one and would do it if needed in a flash
 
Drumaniac said:
It is worth it I have one and would do it if needed in a flash
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Well the tech kind of hinted that it might not be worth it, because this receiver is not a high value piece... I like the aesthetics of it, although I had not heard it working yet without the overpowering hum. I know it is not a high powered receiver, but I don't really need a high powered one. I have a G9000 but never go above volume 2 or 3 for example.
 
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red71rum said:
The problem I am having is that there is a very loud hum coming from both speakers.
Click to expand...

MAYBE IT DOESN'T KNOW THE WORDS!!

- I'll see myself out.

I've got nothing electronically to add other than I'm sure these guys have probably already figured it out.

Great looking receiver! Good luck with teaching it the words to your music. ;)
 
avionic said:
A CR- 620 with NS-690's got me hooked on YAMAHA back in my high school years in the mid 70's ..
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My parent’s Onkyo TX 2500MKII got me started in the 70s and 80s also, of course I cannot remember the speakers all of the sudden though.

Edit - I think the speakers are 3M Revere Wollensack speakers.
 
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