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New B2 for complete rebuild.

Discussion in 'Yamaha' started by belgianbrain, Oct 6, 2017.

  1. belgianbrain

    belgianbrain Super Member

    Messages:
    1,254
    Location:
    Greater Toronto Area, Canada
    Settled on Vampire BP-HEX (about $15 each with current sale) for the binding posts and CMC for the RCA jacks ($6.50 each).
     

     

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  2. bmanone

    bmanone Active Member

    Messages:
    144
    Location:
    Calico Rock, Arkansas
    belgianbrain,
    How's the project coming along? By the way I use the Schiit Bifrost Multibit and Schiit Freya. Currently using them with a repaired and recapped P2200 I picked up off Ebay a month or so ago. Sounds really great to me.
     
  3. belgianbrain

    belgianbrain Super Member

    Messages:
    1,254
    Location:
    Greater Toronto Area, Canada
    The project goes slowly. I've been working on the rear panel lately, which is very time consuming. I think I'm done now. New IEC power connector, new binding posts, and new RCA jacks for the input. Used a solid brass plate to mount the brass binding posts.

    IMG_20171212_201316.jpg
    IMG_20171212_201450.jpg IMG_20171212_201306.jpg
     
    nyhifihead likes this.
  4. rottalpha

    rottalpha Yamaholic

    Messages:
    1,811
    Location:
    Middle of Crook County
    nice work. I thought that the speaker posts were separated from the chassis on this amp? Am I wrong?
     
    Last edited: Dec 12, 2017
  5. Mr. Yamaha

    Mr. Yamaha Not so much Yamaha lately...

    Messages:
    898
    Location:
    Amsterdam Area, The Netherlands
    Ouch, it looks like there was some chassis cutting involved :eek:
     
  6. belgianbrain

    belgianbrain Super Member

    Messages:
    1,254
    Location:
    Greater Toronto Area, Canada
    Yep. It's the rear panel, so I figure why not go all-in and do it right. :biggrin:
     

     

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  7. Bert 1100

    Bert 1100 Super Member

    Messages:
    1,176
    Location:
    Planquiri, Switzerland
    I completely agree ! Great work !
     
  8. belgianbrain

    belgianbrain Super Member

    Messages:
    1,254
    Location:
    Greater Toronto Area, Canada
    Thought I would make major progress on this over the holidays. :rflmao:

    Finally got back to it this weekend and did the two power transistor boards and sinks. Cleaned everything. Replaced the 0.22 Ohm resistors in the signal path with Mundorf MResist Supreme. Changed the 50nF green cap with Panasonic polyproylene.

    In this B2, I have the unpainted heat sinks that use mica insulators, so I replaced the insulators and heat sink grease with Aavid Thermalloy Thermasil insulators (Mfg. P/N 53-03-2G).

    20180114_121658.jpg 20180114_121706.jpg 20180114_121740.jpg 20180114_121758.jpg
     
  9. belgianbrain

    belgianbrain Super Member

    Messages:
    1,254
    Location:
    Greater Toronto Area, Canada
    I fired the power supply board up yesterday to adjust the +/- 85v supply. The driver boards and power VFET boards are currently disconnected.

    CLICK. BOOYEAH.
     
    Last edited: Feb 4, 2018
    zaibatsu likes this.
  10. Vint Age

    Vint Age B-1 With Yamaha

    Messages:
    2,221
    05 The VFETs 01.jpg

    :thumbsup:
     
  11. belgianbrain

    belgianbrain Super Member

    Messages:
    1,254
    Location:
    Greater Toronto Area, Canada
    The rear 3/4 of this amp is done! On to the driver boards and then the meter boards.
     

     

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  12. belgianbrain

    belgianbrain Super Member

    Messages:
    1,254
    Location:
    Greater Toronto Area, Canada
    Well, spring/summer sure took the wind out of my sails! But, free time is mine again as the weather gets cold.

    Driver boards are done. Meter board is done.

    I only have the last 10% to go so it should be complete in a couple of weeks. I'll post some finishing photos and thoughts soon.
     
  13. Bert 1100

    Bert 1100 Super Member

    Messages:
    1,176
    Location:
    Planquiri, Switzerland
  14. belgianbrain

    belgianbrain Super Member

    Messages:
    1,254
    Location:
    Greater Toronto Area, Canada
    Alright. I ran into a snag trying to adjust the driver boards. Basically, I replaced all resistors in the signal path, many fusible resistors, and all capacitors I had polyproylene replacements for. I also changed the big electrolytic with Nichicon Muse.

    I have unit assembled with VFETs removed. Only one VFET board and driver board is installed with 10k resistor between PG and NF and 10K again between NG and NF to simulate presence of VFETs for rough adjustments.

    DC balance can be set to zero with VR101, but bias remains at zero regardless of VR102.

    Front power meter for the installed driver board stays elevated at about 0.01W (this one has me a bit perplexed as how does signal escape FET board with no FETs installed?).

    I took some readings and I get the following:

    +B2=85V
    -B2=-85V
    +B=60V
    -B=-60V
    PG=15V (a tiny bit high, should be 13.5)
    NG=-1.3V (very low, should be -13.5)
    NS=0
    NF=0
    PS=0

    Now both driver boards seem to do the same thing, which really has me scratching my head. I've rebuilt these driver boards before in another unit without issue. I'm also careful to measure each component I remove and measure each replacement part just to make sure it's a match. Yet, if the issue is on the driver board, it seems I made exactly the same mistake on both driver boards. :dunno:

    I'd appreciate any suggestions to help speed up this diagnosis.
     
  15. belgianbrain

    belgianbrain Super Member

    Messages:
    1,254
    Location:
    Greater Toronto Area, Canada
    Penance for carelessness. :). Thanks to Avionic for suggestions on repairing this. It is not pretty but it works.

    Now that both driver boards are fixed I can finally finish this amp.

    20181212_094806.jpg
     
  16. avionic

    avionic " Black Knights " Subscriber

    Messages:
    44,597
    Location:
    Fort Dodge, Iowa
    Is the rear switch set to internal or external.
     

     

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  17. avionic

    avionic " Black Knights " Subscriber

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  18. rottalpha

    rottalpha Yamaholic

    Messages:
    1,811
    Location:
    Middle of Crook County
    they did away with blue coating for all B-2s with serial number greater than 4249. That is what I understand. Any JDM B-2 with 5000+ serial number that I have seen, does not have the blue coating.
     
  19. belgianbrain

    belgianbrain Super Member

    Messages:
    1,254
    Location:
    Greater Toronto Area, Canada
    Yep , no blue coating in this B2. It had mica insulators on the VFETs. Replaced them with Aavid Thermalloy Thermasilinsulators. They work great if you don't over tighten, which took me awhile to learn. Good thing I bought extras.

    B2 works now! Will post a few pictures after I adjust the bias with my THD analyzer.
     
  20. belgianbrain

    belgianbrain Super Member

    Messages:
    1,254
    Location:
    Greater Toronto Area, Canada
    Here is what the driver boards looked like when they were done. Literally every passive component was changed except for varistor diodes. Resistors are all metal film except for a few Takman Rex carbons in the signal path.

    I focused only on things that affect sound or reliability in this B2. So, I only changed electrolytics on meter board and nothing else. Input switch board was not touched because it is bypassed with driver boards wired directly to new jacks on the rear. This board only functions now to switch between two speaker outputs.

    20181205_203609.jpg

    20181205_203601.jpg
     

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