Want to salvage a Sansui 5050.

Discussion in 'Exclusively Sansui' started by imation_nation, Dec 14, 2018.

  1. imation_nation

    imation_nation Member

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    Hi,
    That is an interesting idea I had not thought of. I am not sure it would physically work though. The output transistors are plugged in to a socket which is attached to the heat sink.From what I saw based on the dimensions of the cases for the old vs new, I do not think the new would physically fit? Perhaps I am missing something. Isthere a work around for the dissimilar sizes?

    Thanks for your assistance. This is quite the daunting task. It has been fun though.
     

     

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  2. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Aha - I had not realised that the originals were TO-66 - wait one - I'll provide some new part numbers...

    For 2SA765 (PNP)
    https://www.mouser.co.uk/ProductDetail/ON-Semiconductor/MJE15031G?qs=sGAEpiMZZMshyDBzk1/Wi/PUgtclNldljZTWnEBZ5vI=

    For 2SC1445 (NPN)
    https://www.mouser.co.uk/ProductDetail/ON-Semiconductor/MJE15030G?qs=sGAEpiMZZMshyDBzk1/Wi/PUgtclNldlrLSDWXqsht0=

    These are TO-220 replacements, but this package was designed to be a mechanically friendly equivalent to the obsolete TO-66 package - you just need to bend the legs of the replacements a bit, and use a new insulating kit - which you will need to buy as a separate item. ;)
     
    Last edited: Dec 19, 2018
  3. imation_nation

    imation_nation Member

    Messages:
    67
    Ah, very interesting. It took me awhile to figure out how a TO-220 cased transistor would work with the TO-66 transistor socket that is mounted on the 5050 heat's heat sink.

    (This is what my TO-66 transistor sockets look like.)
    https://www.ebay.com/i/162543938220?chn=ps

    Then I realized the "case" of the TO-220 transistor is the collector and just screwing it on to the TO-66 socket would probably work. I'm not sure what to do with Pin 3 which is the collector also. I would guess that I would just cut it off?

    Am I on the right track with this?

    Thanks again.
     
  4. imation_nation

    imation_nation Member

    Messages:
    67

    Oooopsies, my bad that should read PIN 2 is the collector.
     
  5. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Yep, that's it. ;)

    If you have a search around on AK or anywhere, you should be able to find pictures of how it is done, and looks afterwards.

    If you look at the pictures in this thread
    http://audiokarma.org/forums/index....00-driver-boards-f-2029.841122/#post-12044902

    The silk screening on the boards shows you the idea.

    (I am sure there are better pictures somewhere showing the transistors in place).
     
    Last edited: Dec 19, 2018
    milo63 likes this.
  6. imation_nation

    imation_nation Member

    Messages:
    67
    Good news! I ended up replacing all of the 2SA726’s on the driver board. I new one was bad for sure. Since they were on the top ten transistors to replace here on AudioKarma, I replaced them all. I also replaced all of the electrolytics on the driver board.

    When I powered it on, I heard the relay click on and sure enough, one of the channels is working now. I know the output transistors on the other channel are bad so hopefully when I get some new output transistors I’ll get both channels back.

    Should I replace the other transistors on the driver board also?

    There are two 2SD438‘s, two 2SB560‘s paired and two 2SC1951‘s
     

     

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  7. imation_nation

    imation_nation Member

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    Been awhile since I posted on this topic. I have done a lot of work on this 5050. Good news is I now have both channels working. Yay!!

    Bad news is, the right channel is a touch distorted. I checked the bias on the output transistors per the service manual instructions. The left channel is perfect at 15 mv. The right channel is 0v and the trim pot has no effect.

    I don’t really understand how the bias circuit works. I would take any advice or direction if anybody has any.

    Thanks.
     

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