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Yamaha B-2 restoration journey

Discussion in 'Yamaha' started by Mr. Yamaha, Nov 16, 2016.

  1. jeromach

    jeromach With sufficient thrust, ducks fly just fine

    Messages:
    1,183
    Location:
    O<erveen, the Netherlands
    Yes, same KG's :)

    The pcb needs a very slight adaptation; the lugs of the KG's are a little wider than those of the old Nippons. It would of course be possible to cut a little off of the lugs too, but that would diminish the contact surfarce, so I decided to adapt the board.

    [​IMG]

    Here with one KG fitted;

    [​IMG]

    Ah, and at the back side I scraped away a small amount of the green coating, to take care there was the same contact surface, all in all barely visible;

    [​IMG]
     
    Mr. Yamaha and Oilmaster like this.

     

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  2. Mr. Yamaha

    Mr. Yamaha Not so much Yamaha lately...

    Messages:
    898
    Location:
    Amsterdam Area, The Netherlands
    Looks great!
     
  3. belgianbrain

    belgianbrain Super Member

    Messages:
    1,254
    Location:
    Greater Toronto Area, Canada
    Mr. Yamaha,

    What are those RCA input jacks and binding posts you used?
     
  4. Mr. Yamaha

    Mr. Yamaha Not so much Yamaha lately...

    Messages:
    898
    Location:
    Amsterdam Area, The Netherlands
    Don't know exactly from the top of my head, but it's somewhere mentioned in this thread.
     
    Oilmaster likes this.
  5. Mr. Yamaha

    Mr. Yamaha Not so much Yamaha lately...

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    898
    Location:
    Amsterdam Area, The Netherlands
  6. Oilmaster

    Oilmaster Drillers go deeper Subscriber

    Messages:
    1,255
    Location:
    Paris & The Hague
    So...... how do the majestic KG sound ???
     

     

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  7. rottalpha

    rottalpha Yamaholic

    Messages:
    1,811
    Location:
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    Like any other "DC Sound" ... :biggrin:

    Almost didn't recognize you Oilmaster, nice avatar :)
     
  8. Oilmaster

    Oilmaster Drillers go deeper Subscriber

    Messages:
    1,255
    Location:
    Paris & The Hague
    Linking the right image to the name & profession :)
     
    Last edited: Nov 27, 2017
    The Fez likes this.
  9. Mr. Yamaha

    Mr. Yamaha Not so much Yamaha lately...

    Messages:
    898
    Location:
    Amsterdam Area, The Netherlands
    They sound great :bigok: I think less boomy, but maybe a bit early to tell.
     
  10. spaghetti

    spaghetti Active Member

    Messages:
    386
    Thanks to all contributors of this amazing thread, I am working on a recently purchased B2 and I am finding so much useful information here.

    Regarding the service manual, I found a very nice PDF version on www.manualslib.com, which comes in color and in high definition (~20Mb download), much better than the other available on hifiengine & co.
     
    jeromach and Mr. Yamaha like this.
  11. rottalpha

    rottalpha Yamaholic

    Messages:
    1,811
    Location:
    Middle of Crook County
    hi Gang, quick question regarding the B-2 driver boards, respectively the R147, R149 voltage divider:
    On a US model that I have, with a later, 10k+ serial number, the actual resistors are 1k each, an even split. On the older <3k serial number units from Japan On at least two of them, the R values match the schematic (R147 =1.5k, R149 =470R)
    is anyone aware of a service bulletin that accounts for this change in later models?
    boards numbers are different as well
    Older: NA06747
    Newer: NA06811

    is anyone nere aware of this change, or has noted the different (from schematic) value resistors?

    @Oilmaster would you happen to be aware of this change?
     
    Last edited: Jan 2, 2018

     

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  12. rottalpha

    rottalpha Yamaholic

    Messages:
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    hi Spagetti, what serial number is your unit and would you please look at R147 and R149 when you are doing the driver boards? Also, is your unit US, EU or Japan?
     
  13. Oilmaster

    Oilmaster Drillers go deeper Subscriber

    Messages:
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    Location:
    Paris & The Hague
    I don't think it's a big deal all together.

    1) During normal operation it does not impact the bias circuit's current or voltage values, as the voltage dividier is not active while the total resistance sum remains the same. (in fact, it's not a voltage divider)

    2) During start-up, when the +/-B2 power rails turn on later than the +/-B rails, then there is a minor impact due to the fact the bias circuit (fed via D112/113), since the series resistance from rail to rail will be 1kOhm higher, though that is relatively irrelevant due to R153 (33K) and VR102 (100K max) which dominate by far the DC resistance in that loop.

    Frankly, the purpose/benefit of that mod escapes me.
     
    Mr. Yamaha likes this.
  14. spaghetti

    spaghetti Active Member

    Messages:
    386
    @rottalpha right now I can't do that, I'll be back home on friday evening then I'll let you know for sure. I think my serial number is in the range of 4XXX, but I may be wrong, the SN I have in mind could be from my Sansui BA-F1 I've been working on recently...
     
  15. rottalpha

    rottalpha Yamaholic

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    Location:
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    Thank you Sir!
    It looked like a voltage divider to me, but yes the sum of total resistance is the same.
     
    Mr. Yamaha likes this.
  16. Mr. Yamaha

    Mr. Yamaha Not so much Yamaha lately...

    Messages:
    898
    Location:
    Amsterdam Area, The Netherlands
    In my European B-2 with serial no. 4027 the color codes of those resistors are as follows (R147 on top):

    Capture.JPG
     

     

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  17. rottalpha

    rottalpha Yamaholic

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    Thank you!

    out of curiosity, what is the board model number for yours?

    I asked the question, but I think I can answer it for myself...I do have a high serial number (>9000) Japan unit. The US unit is >10000. I just need to pop the hood on the Japan unit.
     
    Mr. Yamaha likes this.
  18. Mr. Yamaha

    Mr. Yamaha Not so much Yamaha lately...

    Messages:
    898
    Location:
    Amsterdam Area, The Netherlands
    Capture.JPG
     
  19. rottalpha

    rottalpha Yamaholic

    Messages:
    1,811
    Location:
    Middle of Crook County
    yep, same board version as the Japan, early serial number boards I have. So It is based on early vs later unit serial numbers rather than the market region.
    your unit has the blue heatsinks, correct?
     
  20. Mr. Yamaha

    Mr. Yamaha Not so much Yamaha lately...

    Messages:
    898
    Location:
    Amsterdam Area, The Netherlands
    Yes, the blue ones. I will never forget: no silpads and no mica plates, just thermal paste :D
     

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