Yamaha C-80 issue

2

2tumsup

Well-Known Member
Symptoms showed up late last night and confirmed again this morning playing vinyl.
On startup with only a few minutes of idle time the left channel was much weaker(about one third of the volume of right channel) and after 5-10 minutes of playing time it returned to normal but after another 5-10 minutes or so the issue returned and stayed that way until shutdown which was at end of album.
I switched from phono to DAD and it functioned normally. When switching from stereo to mono both channels same volume. Those facts made me eliminate the amp, tt and speakers but of course I could be wrong. No balance controls on the amp.
So with my very limited knowledge and ability I'm thinking an issue with the phono board in the C-80? Was playing in MC mode with my PF-1000.
Help, thoughts, suggestions greatly appreciated.
Thanks in advance
 
Using the mono function does not eliminate the turntable, it combines left and right and tells you nothing about the turntable output. Try swapping the left and right RCA connectors of the turntable. The turntable is good if the left channel is still the problem. Try using the MM mode, the signal will be very weak but you should be able to tell if there's a problem. Possibly exercise the phono switches to see if that clears things up.

Craig
 
Have you ever had your C-80 worked on? It will likely suffer from some cracked solder joints by now. I had similar issues to what you describe. I took it to the shop and it was all due to the cracked solder joints. That makes sense as the problems can come and go as the solder joints expand due to heat. It was well worth the repair cost; the C-80 is fantastic!
 
Its most likely and issue with the MC amplifier. Hooking your MC cart to the MM input will probably verify the issue.
 
Check the balance control and turn it several times in each direction. A bit of dust in mine wasn't noisy but did affect levels until I worked the control. Check, even though it *seems* to be phono-related.
 
Chris Brown said:
Have you ever had your C-80 worked on? It will likely suffer from some cracked solder joints by now. I had similar issues to what you describe. I took it to the shop and it was all due to the cracked solder joints. That makes sense as the problems can come and go as the solder joints expand due to heat. It was well worth the repair cost; the C-80 is fantastic!
Click to expand...

I second this as a good place to start.

Mine too had some cracked or cold solder joints where the input/output jacks solder to the board. The previous owner brought the paired M-80 amp to a shop multiple times to fix the intermittent channel, but they never could get it to act up on the bench. And, with good reason, since the problem had been in the pre amp all along.
 
avionic said:
Its most likely and issue with the MC amplifier. Hooking your MC cart to the MM input will probably verify the issue.
Click to expand...

Thanks Dave - Was away for the weekend and unable to try any further testing until this morning. I turned the system on and started playing an album. Everything working ok thru entire album. Before I started I turned the cartridge selector switch numerous times with hopes that it might make a difference. After listening to the album I just left the system on and let it idle for a couple of hours and then went to use it again and sure enough, the issue resurfaced. It was also present when I switched over to mm mode.
I will bring it to my tech and advise to focus on the MC amplifier and possibly cold solder joints elsewhere. Is there any particular component in the MC amp to check?
Going to miss it. It is my favourite pre by far
 
2tumsup said:
It was also present when I switched over to mm mode.
Click to expand...

If it was still present in the MM.You have problems elsewhere. Probably need to remove , disassemble and clean the phono selector slide switch.
 
Did you try exercising the phono gain button on the rear panel ? It may be dirty as well.
 
avionic said:
Did you try exercising the phono gain button on the rear panel ? It may be dirty as well.
Click to expand...


Based on the symptoms of the issue I never even considered that the gain button on the rear could be the cause. I even forgot that there was a gain button on the rear as I never adjusted it since ownership. I gave it a quick shot of deoxit and exercised the button 10-15 times.
I left the system idle overnight and played it the next morning - problem solved. I turned the system off and repeated the idle scenario again the next day to make sure. Again no issues, system is functioning properly.
Dave, you are the best! Once again, your expertise has solved my problem. Thank you, thank, thank you!
If you're ever in Atlantic Canada, dinner is on me.
Thanks to all for your suggestions
 
The C-80 and C-85 are basically the same pre-amp circuitry on the inside. Just different cosmetics on the outside.
 
So my outs rca jacks are loose INSIDE the module. The module seems fine, my father and i resoldered them to the pcb. They are nice and secure. But the actual rca wiggles inside of the actual module.

Is there anyway to address that without having to sacrifice the module?
 
whoaru99 said:
presuming you mean the RCA jack module?
Click to expand...

The plastic module is well soldered into the pcb. Somewhow the actual gold circular jack is loose inside the plastic moddule. It wiggles.

Ive seen the mods people do with the rca jacks from parts connection. Lol, trying to avoid that. I dont understand how that works with the board.
 
The gold outer RCA shells are loose within the jack..There is a clip or wedge within the connector that is bent.
 
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