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Yamaha C-70 Project

Discussion in 'Yamaha' started by sonavor, Dec 16, 2016.

  1. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,800
    Location:
    Fort Dodge, Iowa
    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.
     

     

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  2. Nashou66

    Nashou66 AK Subscriber Subscriber

    Messages:
    1,626
    Location:
    West Seneca NY
    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
     
    Last edited: Jan 20, 2017
  3. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,800
    Location:
    Fort Dodge, Iowa
    I have a vetted source for the OEM Matsushita replacements that I'm not afraid to use. At $14 each.
     
    Last edited: Jan 20, 2017
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  4. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,800
    Location:
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    Those that you listed are not drop-in and will need to be wired in point to point.
     
  5. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,800
    Location:
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    HB2E-DC24 datasheetarchive has a datasheet that shows the pin out.
     
    Nashou66 likes this.
  6. newellville

    newellville New Member

    Messages:
    1
    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!
     

     

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  7. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,800
    Location:
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    Sounds like solder connections. Welcome to AK BTW.
     
  8. Stevedel

    Stevedel Active Member

    Messages:
    345
    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.
     
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  9. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,800
    Location:
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  10. Stevedel

    Stevedel Active Member

    Messages:
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  11. Ihazbike

    Ihazbike New Member

    Messages:
    4
    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.
     

     

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  12. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,800
    Location:
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    Do all inputs exhibit the same right channel issue?
     
  13. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,800
    Location:
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    How about in tone defeat mode?
     
  14. Ihazbike

    Ihazbike New Member

    Messages:
    4
    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.
     
  15. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,800
    Location:
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    This answer is rather vague.
    Are you getting any sound from the RT channel?
     
  16. avionic

    avionic " Black Knights " Subscriber

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    Location:
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    I need to know exactly whats going on. On both Left and Right channel.
     

     

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  17. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,800
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    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.
     
  18. Ihazbike

    Ihazbike New Member

    Messages:
    4
    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.
     
  19. Ihazbike

    Ihazbike New Member

    Messages:
    4
    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.
     
  20. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,800
    Location:
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    If it acts up again I would suspect either a cold solder connection or a dirty switch/relay contact.
     
    Last edited: Nov 5, 2018

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