Sansui B2101 - DC voltage gone crazy 10V++ and something missing on board.

Discussion in 'Exclusively Sansui' started by Steven Sze, Oct 4, 2017.

  1. Steven Sze

    Steven Sze New Member

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    To owners of Sansui B2101,

    I need your kind help to snap a clear photo of the bottom of board 4619(the one with the heatsink).. Im not sure why is one part of the circuit being cut.

    About a year ago I bought this Sansui Pre and Power B/C 2101 for about $300. Thought I had a good deal, end up the power amp B2101 is faulty.. protection light stays on.. (long story short - seller dissappears).

    Opened up saw its has bèen recapped with the lousiest capacitor ever...some china crap. I spend another couple of hundred to buy new capacitors. Basically replaced all the capacitors except for the 4 big 10,000 uf ones.

    After recapping still the same problem protection light on all the time. The Bias adjustment stays at about +- 10V! when in service manual stated it should be about +- 5mV!

    I've no technical back ground so the most I can only do is recap. so I put it a side for almost a year..in between i sent to 2 techinican.. one doesnt want to do after checking and another took more than 3 months and did nothing. So I took back the amp chuck it in the storeroom.

    [​IMG] And Couple of months ago I took the amp out and I found out that 1 rectifier diode is missing from each board :/ i replace with 1N160 (is this ok?)


    [​IMG] Anyway I just realised that below the power amp board 4619 ( the one with the sink) one of the circuit was cut.. I need someone with same amp to help me to take a photo of the bottom.Also I need a full photo to see where the 3 wires from PSU goes onto the 4619.

    DSC04141.jpg
    someone gave me a photo of his circuit, looks a bit different but it's connected using a wire, Im still kinda lost now if I should connect it back or leave it as it is.

    Can someone provide me a photo of this part, and full photo of where the external wire should be soldered into the board? I suspect previous guy may have switch it.


    I need to check to see if everything is in order before I can proceed to next step.

    Please help.. tq
     
  2. BigElCat

    BigElCat AK Subscriber Subscriber

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    I have this combo. My B-2101 is in the same boat, won't come out of protection mode. I could get it to come out of protection, but the left channel was weak and scratchy.

    I'm pretty sure it's all original/unmolested.

    Would you be able to see what you want with a side panel removed ?
     
  3. BigElCat

    BigElCat AK Subscriber Subscriber

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  4. Ronito6

    Ronito6 Well-Known Member

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    Looks like Sansui factory mods.
     
    slimecity and Hyperion like this.
  5. BigElCat

    BigElCat AK Subscriber Subscriber

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    Same board, same orientation. It has a jumper, but it goes to a different spot.

    DSC00395.JPG
     
  6. BigElCat

    BigElCat AK Subscriber Subscriber

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  7. LBPete

    LBPete Rolling Along Subscriber

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    Very nice amps. Please post the serial numbers for the database. Click on the link in my signature block.

    - Pete
     
  8. SansuiJavier

    SansuiJavier New Member

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    Location:
    Valencia (Spain)
    mine is B2102, board should be similar, was also in protection, I recap and changed the trimpots (in this model it is highly recommended for a correct adjust), fortunately it worked
    2102 placa 4619.jpg
     
    Last edited: Oct 5, 2017
  9. avionic

    avionic " Black Knights" Subscriber

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  10. BigElCat

    BigElCat AK Subscriber Subscriber

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    SansuiJavier's board does not have a jumper in that spot.

    I have a jumper that terminates on one side same as Avionics, but the other end goes to a different trace.

    IMHO, Steven Sze should leave his without a jumper. The trace cut was done by Sansui.

    It's my understanding that these circuits are modded versions of the illustrious B-2301 amps. I'm not sure how I came to this conclusion.

    I know it shares certain components (like the speaker relays) with it's expensive big brother.
     
  11. Steven Sze

    Steven Sze New Member

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    Thanks for the photo :)
     
  12. Steven Sze

    Steven Sze New Member

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    Wow.. thanks for the photo.. i think my board is similar to yours. Im gonna try your jumper.
     
  13. Steven Sze

    Steven Sze New Member

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    I
    I think you may need to do a recap.

    Btw I think your board and mine is quite similar. Can i see where the wire goes for both board pls.
     
  14. BigElCat

    BigElCat AK Subscriber Subscriber

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    I'm working 12 hours on, 12 off until Monday.

    I'll take the bottom off the B-2101 when I can.

    I have a USB microscope, but it won't take still photos since I switched to Windows 10. If I can figure this out, it will help. I have a heck of a time taking close up shots with my Sony hand-held camera.
     
  15. Steven Sze

    Steven Sze New Member

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    Screenshot_20171008-110041.jpg it would be great if i can see where this wires goes to for both sides. Appreciate your help.
     
  16. BigElCat

    BigElCat AK Subscriber Subscriber

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    One white wire goes past the edge of the board and joins to a harness going to the front panel of the amp.
    DSC00404.JPG
    DSC00399.JPG
    DSC00400.JPG
    DSC00402.JPG
    DSC00403.JPG
     
  17. BigElCat

    BigElCat AK Subscriber Subscriber

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    We can't see where the red and blue wires poke through. They're behind the aluminum bracket that holds the output transistors.

    The white wire comes through smack in the center of the board...center of picture. It's surrounded by two white circles...like a bull's eye.

    DSC00406.JPG
     
  18. BigElCat

    BigElCat AK Subscriber Subscriber

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  19. BigElCat

    BigElCat AK Subscriber Subscriber

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    FYI...we're setting the DC offset, not bias.
     
  20. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Just FYI BigElCat - In the second (& third) pictures of post #16 - the soldering on the terminals for the red and blue wires is really terrible - you might want to attend to that next time you have a soldering iron in your hand. ;) - the first picture (other channel?) looks OK.

    (I know these are pictures of your B-2101 - not the OP's basket case). :)
     
    Last edited: Oct 8, 2017

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