First restore effort... C-70/M-70

Discussion in 'Yamaha' started by dino74, Jun 11, 2018.

  1. dino74

    dino74 New Member

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    I previously posted about getting a B-2x/C-2x and I'm going to restore those eventually but I've never done it before. So, I ran across a M-70/C-70 combo for $150 and figured it be a good place to start. If I totally mess it up, I wouldn't lose too much. Pics below, C-70 has some scratches on top and the M-70 is decent. In pic 1310, is that an example of the infamous glue in the lower left corner?
     

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  2. avionic

    avionic " Black Knights " Subscriber

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    Yes
     
  3. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    In the M-70 the 12v power supply board is the one that will have lots of that Sony bond glue that needs to be removed. There were lots of corroded parts there in my M-70.

    Also, on the "Control-1" pcb there is a safety cap that must be replaced. C607. In my unit it was a 0.47µF/250v but in the US models I think that it is different. ?0.22µF/250v? In any case it must be replaced, it can explode.
    https://www.mouser.de/ProductDetail/Panasonic/ECQ-U3A224MG?qs=sGAEpiMZZMv1cc3ydrPrF%2bfZ13WJ/r1/0vmwaluRlFs=
    https://www.mouser.de/ProductDetail/Panasonic-Electronic-Components/ECQ-U3A474MG/?qs=sGAEpiMZZMvQAn3cSZoTr1%2b0Ye1BktuzFq%2bm14xyTdw=

    While you are in there it won't hurt to replace the 3x smaller 6800pF/250v safety caps. C608, 609 & 610.
    https://www.mouser.de/productdetail/panasonic/ecq-u2a682kl?qs=sGAEpiMZZMv1cc3ydrPrF0%2bjlB8SXIRuFjuQdipUHOg=

    You got those 2 units for a good price. They're pretty good equipment.

    Cheers,
    James

    edit: The replacement cap must be a "safety" cap, X1 or X2 rated.
     
    Last edited: Jun 13, 2018 at 1:05 AM
  4. dino74

    dino74 New Member

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    Thanks for the info about the safety, I'll have to look at the schematic to see what the general model uses.

    He wanted $250 and thought I'd offer $150, a part of me wanted him to say no so I wouldn't have to drive and pick them up.
     
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  5. avionic

    avionic " Black Knights " Subscriber

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    Last edited: Jun 12, 2018
  6. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Just smoke and burn? Why heck, that's not so bad...:eek:.

    In my M-50 it exploded the first time that I switched it to 240v after I moved over here. Lucky for me it didn't do any extra damage. I believe that @Oldsansui441 had one that burned and took most of the PSU with it.

    Cheers,
    James
     

     

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  7. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Here is how the 12v psu board looks with all of that glue caused corrosion...

    DSC05081.jpg DSC05084.jpg DSC05087.jpg DSC05093.jpg DSC05095.jpg

    Cheers,
    James
     
  8. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

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    Those two are a nice score for 150 dino74, plenty of clean power. They are worth putting some time into. Good call by the other guys referring to the X2 safety cap.

    Yes correct, this is what happens shown below, very nasty business.

    Yeah that glue was extra corrosive on yours Bratwurst7s.
     

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  9. dino74

    dino74 New Member

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    Location:
    Oceanside, CA
    Before I start taking this thing apart, I wanted to see what state it was in. It works but a couple of leds are burnt out. The weird thing my bedroom is wxc-50 -> mx-35 -> elac so I tried wxc50-> m-70 -> elac. I'm not sure how to explain it but I didn't like it as much as the MX-35.
    IMG_1326.jpg
     

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