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Burned Yamaha B-6

Discussion in 'Yamaha' started by Dominic N, Nov 16, 2018.

  1. Dominic N

    Dominic N New Member

    Messages:
    22
    Location:
    Holland
    So I have bought something nice to restore again a Yamaha B-6 that has been on fire the inside smells terrible.
    The capacitor that should have been replaced in the recall on all 220v models has caught fire and damaged the print. image-03-11-2018_17-12-46.jpg DSC_0054.JPG
     
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  2. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    2,212
    Location:
    France
    Yes , very well known problem

    I have made many B6
     
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  3. toxcrusadr

    toxcrusadr AK Subscriber Subscriber

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    You are a brave man.
     
  4. avionic

    avionic " Black Knights " Subscriber

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  5. avionic

    avionic " Black Knights " Subscriber

    Messages:
    44,560
    Location:
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    Oh boy. Hope you didn't pay a whole lot. Not looking good. Post photos after you get all that soot cleaned up. Output transistors should still be good. They're getting hard to find nowadays.
     
    Last edited: Nov 16, 2018
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  6. avionic

    avionic " Black Knights " Subscriber

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    I have seen some of the 120VAC models burn the RIFA " across the line" caps. On M-50 and M-70 amplifiers.
     
    Last edited: Nov 16, 2018
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  7. avionic

    avionic " Black Knights " Subscriber

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    Got a few under my belt as well.
     
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  8. rottalpha

    rottalpha Yamaholic

    Messages:
    1,803
    Location:
    Middle of Crook County
    I like your spirit of adventure :)

    not a very complex board...as in not difficult to reproduce.
     
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  9. rottalpha

    rottalpha Yamaholic

    Messages:
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    are there any unobtanuim parts in the B-6? besides the PSU boards:biggrin:
     
  10. avionic

    avionic " Black Knights " Subscriber

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    One that I know of. It looks like its probably charcoal. IC401 IG04080
     
  11. avionic

    avionic " Black Knights " Subscriber

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    44,560
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    Well maybe not.. Its the little blue component.

    DSC_0054.JPG DSC04243.png
     

     

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  12. OMGCat!

    OMGCat! AK Subscriber Subscriber

    Messages:
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    Man those caps are bad news. I was watching a guy work on an old Macintosh computer the other day and smoke started pouring out of the case. Opened it up, Rifa cap cracked in half.
     
  13. Dominic N

    Dominic N New Member

    Messages:
    22
    Location:
    Holland
    It is the rifa capacitor that was completely exploded and left a lot of firetracks, it is not my first amplifier that I repair but my first B-6 I now have solder all the print tracks for strength and in the meantime clean the print with some oven cleaner and let some glue flow here and there to give the print some strength again.
    There has also been someone for me who has ventured an attempt, there is also a resistance of 33k 2 watt missing.

    a new fuse holder, resistors and capacitors soldered and this is the result, not new but working fine again.

    Now just clean the amplifier board and replace 2 wrong transistors in the power control. sketch-1542436244179.png sketch-1542436321186.png sketch-1542436244179.png sketch-1542436321186.png
     
  14. avionic

    avionic " Black Knights " Subscriber

    Messages:
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    Location:
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    Is that replacement for the RIFA and X2 rated safety cap?
     
  15. Dominic N

    Dominic N New Member

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    22
    Location:
    Holland
    yes I actually also want to have mkp but I did not have that in stock, so now these capacitors are in it.

    is it a bad choice?
     
  16. avionic

    avionic " Black Knights " Subscriber

    Messages:
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    C401-403 VAC rated. I'd hold out for the MKP. C404 should be X2 rated.MKP ( across the line)
    Don't need any more fireworks.:D
    These are all annotated in the parts list as safety items. ( * )
     
    Last edited: Nov 17, 2018
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  17. avionic

    avionic " Black Knights " Subscriber

    Messages:
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    Is this damaged board working as it should now?
     
  18. Dominic N

    Dominic N New Member

    Messages:
    22
    Location:
    Holland
    Aha okay I did not know, I have to replace it for the right one.
    Yes the positive thing is ..... in any case, he plays again.

    It has to be adjusted for a while but the test points on the service manual do not seem to be right.
     
  19. rottalpha

    rottalpha Yamaholic

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    Location:
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    wait, what???
    you are keeping the board ???

    ya know carbon coducts electron juice, right?
     
    Bill Ferris likes this.
  20. Dominic N

    Dominic N New Member

    Messages:
    22
    Location:
    Holland
    Yes I know, i scrubbed with sandpaper and cleaned it 5 times with an oven cleaner, there is no residue left, just soot.
    The print is good to go.

    There was also a lot of the burnt capacitor on the main board, and this has also been cleaned with oven cleaner.
     

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