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
  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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    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
     
  10. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Any progress?

    Cheers,
    James
     
  11. dino74

    dino74 New Member

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    Not really, work has been busy and I have one other project with higher priority. A pwm controller for my fish tank LED light but that should be done in the next week.

    I starting to plan out my work benches and trying to figure out what I need to buy.
    Found two glass top desks (56"x30" each) on CL that I'll use for electronics and computer.

    I currently have
    Variable temp soldering iron
    Desolder pump
    Rigol DS1052E Oscilloscope
    Various Voltmeters, nothing high end.

    Looking at
    A good meter that can measure capacitance.
    Maybe a signal generator.
    Maybe a transistor tester.

    Edit: I also picked up a M-35 for $15. I'm thinking that would be a better first try than the M-70
     

     

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  12. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    The M-35 will definitely be an easier first try and good practice before you jump into the M-70.

    For testing components a M328 based tester works great. Direct ebay links are frowned upon but if you go to ebay and use
    "Newest version of inductor-capacitor ESR meter DIY MG328 M328 multifunction test" for your search string you will find a good tester for the money.

    I paid 2x the price for an earlier 9v battery powered version and found it to be extremely useful for the price. The new version is half what I paid and is powered through a micro usb port or LiIon battery. (no affiliation, just like it for the price).

    Cheers,
    James
     
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  13. dino74

    dino74 New Member

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    Thanks for the info! Just order one.
     
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  14. amr2

    amr2 Active Member

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    I’m using lcr-tc1. It works great and it have built-in rechargeable Li-ion Battery
     

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