Yamaha B-3 V-fet restoration

Discussion in 'Yamaha' started by vintagejapan, Feb 18, 2018.

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  1. vintagejapan

    vintagejapan AK Member Subscriber

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    On the power regulator board I have 2SC1439 V rank, 2SC1775A, 2SA858 V, and 2SA872.

    Will be replacing 2SA858 with 2sa1015, I have not seen current subs for 2SC1439 and 2SA872. I am thinking 2SC2240 and 2SA970 here.
     

     

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  2. rottalpha

    rottalpha Yamaholic Subscriber

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  3. vintagejapan

    vintagejapan AK Member Subscriber

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    Already did look at that great thread (thank you Pete)
    No info about the 2SC1439.

    one substitute is 2sc2229 (obsolete)

    On Another thread I read they can be replaced with 2sc3503/2sa1381 which I do have in hand...

    Or maybe TTC004B?
     
  4. zaibatsu

    zaibatsu Well-Known Member

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    Hi vintagejapan, I used 2SC2705 / 2SA1145 (both -Y) as they have better gain than the currently available 3503 (-D).
    I think the 3503 / 1381 should work fine too though. Open to correction as I haven't finished mine yet.

    I just measured two of my B-3 2SC1439 (-B) pulls from the regulator board, hFE = 77 and hFE = 141
     
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  5. vintagejapan

    vintagejapan AK Member Subscriber

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    Last edited: Jun 20, 2018
  6. rottalpha

    rottalpha Yamaholic Subscriber

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    Sorry, been mostly in transit while reading the thread...

    Yes, the C3503/A1381 should work fine. Used them for the B-1, B-2.

    The TTC/TTA, from Toshiba will have a higher cob than the C3503/A1381. Not sure of the specs of the original.


    If @Oilmaster chimes in, he would be able tho spell it out better
     
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  7. bmanone

    bmanone Active Member

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    I noticed your power supply board has those common anode and common cathode pair diode packages (red and black components between the green and rust mylar caps). I strongly suggest you consider replacing them, I had 3 of 4 of those fail on one of my P2200 power amplifiers. I used these SMC diodes from digikey to replace mine: MBRF 10150CTR (common anode) and MBRF10150CT (common cathode). YMMV
     
  8. vintagejapan

    vintagejapan AK Member Subscriber

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    Thank you for your input. From a quick look the red double diodes are 10DC4 and 10DC4R 400v 1.5A diodes.

    There is also space issue, replacements have to be of same hight of the ones in place.
     
  9. vintagejapan

    vintagejapan AK Member Subscriber

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    When the board is in place there is 2 fuses right next to the diodes. IMG_4895.JPG
     
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  10. bmanone

    bmanone Active Member

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    Yours may hold up better since they are higher voltage rated than the ones in the P2200 (10DC-1 or 10DC-4, and 10DC-1R or 10DC-4R). From your photo it looks like taller diodes would block access to the fuses, but not contact them.
    DSCN0135.jpg
     
  11. vintagejapan

    vintagejapan AK Member Subscriber

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    Work is progressing slowly here, much of my time has gone in researching for suitable parts.
    So far here is what I have done in the power supply board :

    Replaced the C1439/A858 with C4027T/A1552T tried to match those. I IMG_6413.JPG IMG_0595.JPG IMG_4204.JPG
    I used MJE15030 that I had in hand to replace the C1624
    2 more transistors C1775A/A872 were replaced with C2240/A970
    4 1S1885 diodes with 1N4007
    Still waiting for the Zeener diodes to arrive, 2 X 3.3uf/100v film caps and some resistors.

    Thinking to put mica caps in place of the 4 X 47pf ceramic caps

    Then ideally the trimers for adjusting the +/- 85 v which are tricky because need to be accessed while the board is in place.
    there is only about 6mm space on top of the board so not sure anything can fit on top. If someone have knowledge of any trimmer pots like the original that are accessible on both sides please let me know.

    Not finished yet but here is some pics of the board.

    I tested it in place for a few hours today without issues
     

     

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  12. vintagejapan

    vintagejapan AK Member Subscriber

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    The drivers I have in mine are R rated. They measured ok so am thinking to leave them
     
  13. vintagejapan

    vintagejapan AK Member Subscriber

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    Well, after much pondering I have left the transistors on the drive board as is. The power supply board is now finished. Replaced the 3.3uf mylar caps with polypropylene caps. The B-3 even in BTL mode barely gets warm and all boards had no heat damage. After a nice clean up here they are. The sound superb, fast, and less noisy than the B-1 or B-2.
    IMG_8271.JPG IMG_9053.JPG
    IMG_4217.JPG IMG_2724.JPG IMG_9619.JPG IMG_3345.JPG IMG_8944.JPG IMG_6919.JPG
     
  14. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

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    Nice work vintagejapan :thumbsup:.
     
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  15. vintagejapan

    vintagejapan AK Member Subscriber

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    Thank you :). It took longer than usually but glad all went well.
     
  16. vintagejapan

    vintagejapan AK Member Subscriber

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  17. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

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    Great it all went well, bet they sound terrific. Out of curiosity what series are those blue Nichicon caps, l haven't used those before.
     
  18. vintagejapan

    vintagejapan AK Member Subscriber

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    That is a good question! Got those when in Japan a couple of years ago. They were the new 105 degrees for audio series.
     
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  19. Mark B

    Mark B Yamaha Fan Subscriber

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    Your B-3's look great!
     
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  20. rottalpha

    rottalpha Yamaholic Subscriber

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    Lookin' really good VJ. Is never too long if it ends up with success. Congrats! Looking forward for your listning experiences...It will be a while until I get my B-3 Duo ready for prime. Too busy battling Sony deamons at this time.

    out of curiosity re:
    I found my B-1, B-2 whisper quiet...as in I could hear a mouse farth faster than hear any noise from any of the amps. I have yet to hook up a scope and further thinker with the PSUs in these units. Not that they need to but moe out of curiosity.

    Have you hooked up a scope and you find more "noise" comng out of the B-1, B-2 PSUs than from the B-3??
     

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