Want to salvage a Sansui 5050.

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

  1. imation_nation

    imation_nation Member

    Messages:
    77


    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:
    77
    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:
    77

    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
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  6. imation_nation

    imation_nation Member

    Messages:
    77
    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.
     
  8. imation_nation

    imation_nation Member

    Messages:
    77
    Just wanted to update my effort to resurrect my Dad's Sansui 5050. Goal was to replace all of the caps and of course make it work again.

    Started out with no audio. Receiver would not come out of protect mode. Looked like a barn find honestly. Here is what I found.

    I was checking resistance on some various components on the F-2701Power SupplyBoard and noticed that the resistance across F604 (250v, .15A) was 28 ohms and the resistance across F605 (250v, .15A) was 58 ohms. I got the same reading when I pulled them out of the holder. Replaced both.

    Either TR01 or TR03 had failed. I replaced the TR01 - TR04, 2SA726's with KSA992's . After this, the receiver came out of protect mode. However I noticed a bit of distortion on the right channel. Putting the scope on the output, I saw this.

    Sansui 5050 scope bad channel_edited.jpg

    One of the power transistors had failed. I picked up a pair of matching output transistors, although in the end I only replaced the defective one since it seemed to match the original better. After this, both channels sounded good.

    I replaced all of the electrolytic caps, board by board, checking after each one was done to make sure it was working. The receiver sounds awesome now. They are currently paired to my Pioneer HPM100's. Very happy with it.

    The one question I have for anybody is about the panel lights. I replaced all the panel lights with LED's. Cool white. I like the look, but I noticed the light is not completely even across the face. It appears the LED's are a tad to directional. Anybody else notice this??

    I also have a Sansui 9090DB that has no output unless I take out the jumpers and put the input straight into the Main amp. So that is my next project. Pretty sure it is the Dolby board. Pray for me please. :rolleyes: I purchased this system overseas in Japan while I was in the Navy during the 70's.

    Want to thank everyone for their assistance. This place is a goldmine of information. Definitely going to become a subscriber here.
     
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  9. Leestereo

    Leestereo Super Member

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    For the 5050 that I restored with LEDs, it was necessary to orient the LEDs towards the back (i.e., facing the white plastic housing) to achieve a seamless even dial illumination.

    5050 dial lights 2.jpg
     
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  10. imation_nation

    imation_nation Member

    Messages:
    77

    That makes sense. I will definitely try that.

    My 5050 has a crappy vinyl laminate of some type. It is flaking in spots. Yours looks like real wood. Did you refinish the case?

    Thanks for you response.
     
  11. Leestereo

    Leestereo Super Member

    Messages:
    2,217
    Location:
    Ottawa, ON
    The original vinyl wrap that was on the Sansui 5050 consists of 2 layers: the outer layer is easily peeled off (due to the drying out of the adhesive). The inner layer on the wood case itself is quite robust and was left on (surface was cleaned with isopropyl alcohol to remove any adhesive residue). The outer layer was replaced with a nice cherry wood vinyl wrap, e.g., https://www.amazon.com/Tact-Brand-18-Inchx9-Feet-Creative-Self-Adhesive/dp/B00B2734LW.

    5050 case top.jpg

    5050 side final.jpg

    Some Pioneer receivers of this same era also used this type of imitation walnut veneer, and their cases can also be similarly restored, a Pioneer SX-750 with the same cherry wood covering as the Sansui 5050 can be seen via this link.
     

     

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  12. imation_nation

    imation_nation Member

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    Oh wow, that looks so much nicer. Added that to my to do list. Thanks for the link..
     

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