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Does M70/C70 Recap Require a Pro?

Discussion in 'Yamaha' started by Gary D Olson, Mar 18, 2017.

  1. Gary D Olson

    Gary D Olson Skilled Tightwad

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    I have the service manuals and can solder, but is that enough with either of these pieces?
     
  2. Gary D Olson

    Gary D Olson Skilled Tightwad

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    It seems I previously asked this question about the M70 and brutal responded in the affirmative. What about the C?
     
  3. zaibatsu

    zaibatsu Active Member

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    311
    http://audiokarma.org/forums/index.php?threads/yamaha-c-70-project.747782/

    There's a good thread by sonavor here covering the full restoration of a C-70, it should help a lot.
    His component choices are very good too, I'd be inclined to use the same ones.

    It probably goes without saying, but do be really careful with the orientation of parts and when soldering (to not create any bridges etc).
    Any small slip-ups can result in mass damage (I speak from experience sadly!) so triple check everything before powering on again after service.

    Edit - also something you might already know, but make sure you buy all components direct from a reputable electronics source (eg. mouser), don't buy anything off ebay etc - counterfeits galore.

    Also, one of the biggest problems with old Yamaha amps is cold solder joints (they look dull and often have a faint ring / crack around the leg of the component) so it's worth re-touching all those with a spot of fresh solder. I've found that re-melting the existing solder isn't as good usually.

    Good luck!
     
    Last edited: Mar 18, 2017
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  4. avionic

    avionic " Black Knights" Subscriber

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    Probably be able to DIY. If the C-70 is presently working.
     
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  5. Gary D Olson

    Gary D Olson Skilled Tightwad

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    Thanks for the advice. I did read sonavor's thread (twice) and am prepared to follow it as best as possible. Everything will come from either mouser or digikey. Thanks for reminding me to fix cold solders. I'll be sure to take your advise and use fresh solder.


    It does, which makes me all the more nervous. I feel like a paratrooper about to jump out of a perfectly good plane.
     
  6. whoaru99

    whoaru99 Epic Member

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    Did the advice also suggest to replace with component values like are on the board, not just order what the SM calls out?
     
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  7. Gary D Olson

    Gary D Olson Skilled Tightwad

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    I did read that and will give priority to the part on the board, unless it looks like unoriginal.
     
  8. Gary D Olson

    Gary D Olson Skilled Tightwad

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    Location:
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    One more thing. Can these pieces be recapped with just a multimeter? I did recently buy an old oscilloscope but I'm not quite ready to pretend to know how to use it.
     
  9. OMGCat!

    OMGCat! AK Subscriber Subscriber

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    I like to check the components I'm pulling out and putting back in so I'd recommend one of the inexpensive component checkers you can buy on ebay. It's probably rare as anything but I'd kick myself if I had to track down a bad cap or diode that I put there.
    If you're going in may as well do the trimmer pots, heat sink paste as well as spot checking some of the fusable resistors to see if they are holding spec.
     
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  10. Gary D Olson

    Gary D Olson Skilled Tightwad

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    I'll follow your advice. Thermal paste is the reason I'm so cautious. The 1st (and last) time I attempted a recap, the thermal paste I used - leftover from a pc build - contained metal. Poof! A Pioneer SA-8800 was history. But I've learned my lesson and the next one should go perfectly. Right?
     
  11. OMGCat!

    OMGCat! AK Subscriber Subscriber

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    Ha, I hope so. I used to do lots of electronic work but took a bunch of years off and regret to say after the hiatus my first poke inside an amp also ended up with smoking resistors from shorted outputs.

    It happens and is mostly ok as long as you learn from it ya know?
     
  12. Gary D Olson

    Gary D Olson Skilled Tightwad

    Messages:
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    Location:
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    Heh, I hope so too. I really want to bring this M70/C70 combo to it's potential but fear that can't be done by a noob with a soldering iron & multimeter. I'll hire a pro if I don't like the results; hopefully before Tom Ishimoto at Northridge Electronics retires.
     

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