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Yamaha C-80: What Am I Walking Into?

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avantbored

Active Member
Reclaimed a Yamaha C-80, as I sold the first one without really understanding the potential of inverted pre out.

Not a bad price, but not one that I'm singing into the hills on. Anyway, seller stipulated public meet-up. Fine by me! Only how to test?

I brought over-ear headphones, RCA-to-3.5mm cable, my hip DAC, and my phone. Halfway to the meet up, I thought, "Darn, I should have brought a screwdriver."

Sound in both channels. Hiss in the left. Disappeared when operating mono/stereo switch. Present on all line level inputs. Of course, the expected scratchiness.

The seasoned of you probably know what comes next: I opened the cover when I got home, and saw four beautiful bulging caps. Darn! Also, the DSBG had dried and flaked away under the gentle prodding of one of my tools. One of the heat sinks is loose.

Otherwise, PCB looked pretty clean. No burned traces, as far as I could tell. I did the usual pot/switch cleaning.

Hooked up to the proper system. Dead right channel!

Here's some pics. Obviously, I'm looking at re-capping those four mains. Anything else I should be aware of?

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There is one C-60 without plastic covers on main caps and 4 dry caps replaced. (Nichicon 1000uf/63V).
DSBG removed, radiators cleaned and reinstaled with new glue, transistors resoldered.
"Finally I´m trying invert outputs on C-70 with some power amplifiers and speakers. Now I can recognize more punchier and stronger sound."
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Back from the tech with a clean bill of health, but I'm noticing that the left channel has a pronounced white noise hiss on the left channel. Present on all inputs, as well as on Normal and Inverted modes. Any insights appreciated to anyone who reads this belated post. Thanks!
 
avantbored said:
Back from the tech with a clean bill of health, but I'm noticing that the left channel has a pronounced white noise hiss on the left channel. Present on all inputs, as well as on Normal and Inverted modes. Any insights appreciated to anyone who reads this belated post. Thanks!
Click to expand...
Is the hiss present with the TONE BY-PASS button engaged?
 
May have a noisy transistor. :idea:Are you going to take it back to your tech? Or are you going to take a stab at it? :biggrin:
 
If it has a clean bill of health it shouldn't have noise on any inputs. I assume your tech has some sort of warranty? At least contact him and let him know what the problem is.
 
avionic said:
May have a noisy transistor. :idea:Are you going to take it back to your tech? Or are you going to take a stab at it? :biggrin:
Click to expand...

I can confirm the hiss is present with TONE BYPASS engaged and disengaged.

nakmandan said:
If it has a clean bill of health it shouldn't have noise on any inputs. I assume your tech has some sort of warranty? At least contact him and let him know what the problem is.
Click to expand...

Yes, that is the assumed definition! Tech is great but the shop is still getting its sea legs back on after the fires here in LA. Per @avionic's question, just wanted to investigate to see if it could be something on my end that doesn't involve replacing parts (which I don't want to do on my own); driving across town is hellish!
 
avantbored said:
I can confirm the hiss is present with TONE BYPASS engaged and disengaged.
Click to expand...
OK. I would start looking at the Left channel of the NEW CONTINUOUS LOUDNESS and the 6dB FLAT AMP. Prime suspects - opamp in the loudness control IC309A (NJM4558S) or TR301 (2SK389) dual JFET input differential in the flat amp. Going to need to scope out the input and output audio signal of those two components.
 
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Gummed up input selector switches are a problem on these at this age point.
To your tech:
Those tactile input switches are a bitch to access. When in there, they need to be doused in a bath of cleaner multiple times and cycled alot, then lubed.
 
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