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Yamaha C-70 Project

comish4 said:
I have a Yammie to work on one side is suffering from very low output on one side unless the direct button is selected. Just been putting it off. Great work!
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Either a cold solder issue , dirty switch or fouled relay contacts.C-70 or C-50 ? Probably be best to start a new thread for your yamaha.
 
avionic said:
What part number are these ? Start a new thread or your piece.
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There a few that have gold clad contacts

like these

http://www.newark.com/pdfs/datashee...CMP=AFF-CJ-7598510-Newark_element14&source=CJ

you can also get these with the same from the notes

https://www.fujitsu.com/downloads/MICRO/fcai/relays/ry.pdf

I Have bunch of VDC Marquee CRT projectors that use these relays to switch the video signal input. sealed type .

here they are on E-bay.

gold relay contacts

Nashou
 
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Nashou66 said:
There a few that have gold clad contacts

like these

http://www.newark.com/pdfs/datashee...CMP=AFF-CJ-7598510-Newark_element14&source=CJ

you can also get these with the same from the notes

https://www.fujitsu.com/downloads/MICRO/fcai/relays/ry.pdf

I Have bunch of VDC Marquee CRT projectors that use these relays to switch the video signal input. sealed type .

here they are on E-bay.

gold relay contacts

Nashou
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I have a vetted source for the OEM Matsushita replacements that I'm not afraid to use. At $14 each.
 
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Those that you listed are not drop-in and will need to be wired in point to point.
 
I'm new and I'm late to the party -- I just picked up a C-70 and an M-70 over the holidays. They're glorious pieces! I've run into a few of the quirks and nuances you've documented so meticulously (thank you). It's very clean but had power supply issues, relay issues, and the switching doesn't always fully actuate.

I've noticed, though, that after warming up it operates flawlessly. Upon first turning it on I'll only get one channel. Then I turn off the EQ and both work. Then I'll switch the EQ again, adjust balance and volume then it's all good! strange, quirky, beautiful machine -- I'm certain it's female and just needs a gentle touch :)

thanks so much for all your notes!
 
I've had a C-70 since new. It had a recurring problem with left channel dropout. I tried everything. (Anybody know where I can get those small O-rings in the input switching module? I destroyed a couple.) After I treated all of the ribbon connecters with a drop of De-Oxit I've had no more problems.

I use it primarily to convert my record collection to WAV files. It has the best phono preamp section I have ever used.
 
New to audiokarma here, and late to the game with preamp repair, but your post has been incredibly helpful. I am currently in the middle of my own C-70 repair. I've gone through with deoxit several times, replaced the power supply caps, got rid of all the old Sony glue, and lubed the troublesome solinoid switcher (though it seems to work just fine). The one catch is that the right channel is weak/nearly non existent when I hook it up to my M-70. I know it's the C-70 with the issue because both channels work perfectly when i hook up my C-50. I'm going to go through and recap the C-70 completely to see if that fixes anything. In the mean time, any tips I should try to figure out why the right channel might be out or ideas on how to fix it? Willing to try anything to bring this C-70 back to life.
 
avionic said:
How about in tone defeat mode?
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Checked it again and with the parametric tone controls off, the right channel is out from all inputs. But when the tone controls are on, the volume of the channels fades in and out - still favoring one side.
 
I need to know exactly whats going on. On both Left and Right channel.
 
Hook a interconnect cable to" tape record out" (either 1 or 2) on the C-70 to the M-70 main in. Dial down your input attenuators (volume controls) on the M-70. Check for sound quality on both channels. This could eliminate some possibilities.
 
Just tried this, interconnect from tape record out to the M-70, and I get sound. Not very loud, but it is coming from both channels seemingly even.
 
Ihazbike said:
Just tried this, interconnect from tape record out to the M-70, and I get sound. Not very loud, but it is coming from both channels seemingly even.
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Okay so right after I posted my last reply, i switched the interconnect back to the normal pre out, and the right channel came back to life. I have no idea what changed but it's working perfectly now! Ha.
 
If it acts up again I would suspect either a cold solder connection or a dirty switch/relay contact.
 
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