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Sansui Eight Receiver Issue

Discussion in 'Exclusively Sansui' started by jeff's eight, Dec 15, 2017.

  1. jeff's eight

    jeff's eight Member

    Messages:
    75
    Location:
    Phoenician
    I have a receiver which degrades over time (10-15 minutes) to the point of
    it being unusable. I live in Phoenix and have had this with a local mac expert
    who can not seem to locate the issue. Any thoughts for a repair option?
     

     

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  2. KingBubba

    KingBubba "Too Much Stuff" Subscriber

    Messages:
    9,792
    Location:
    Brooksville, Fl.
    If you have another receiver or integrated amp, try coming out of the Eight's pre out into the amp in of the other unit. Run it like this and see if the trouble appears. If it does then you know the issue is in the preamp of the Eight. If nothing happens that way then come out of the second unit pre out and into with the Eight's amp in. Run this and see if the issue happens this way. This way you will know which part of the receiver is having problems.
     
    skippy124 likes this.
  3. Robisme

    Robisme Sansui Enthusiast Subscriber

    Messages:
    11,695
    Location:
    Martinez California
    Some transistors in the power supply may be going bad. I have had to replace a few. I think there is a TO-66 that I have replaced with a TO-220.
    Maybe some CDC9002 or CDC8002 transistors as well.

    Rob
     
  4. jeff's eight

    jeff's eight Member

    Messages:
    75
    Location:
    Phoenician
    Very good idea. I will take a look to see if any have preamp outs.
    I will test those transistors as well. Thank you very much!
     
  5. stereofun

    stereofun Super Member

    Messages:
    1,233
    Location:
    Tucson, AZ
    The Eight has some pretty noisy transistors in the preamp and phono board and one "flying saucer" on the power supply board.

    Is the degradation in both channels ? Is it popping or white noise ? Is it all inputs ? Is it regardless of volume setting ? Any unusual heat radiation (the Eight runs very cool, normally)
     
    dlucy likes this.
  6. jeff's eight

    jeff's eight Member

    Messages:
    75
    Location:
    Phoenician
    The sound becomes increasingly distorted -even not popping. Not sure if in both channels but will check. Ditto on volume. It was in a restricted space though. I will retest in an open setting at varying volumes.
     

     

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  7. blhagstrom

    blhagstrom Mad Scientist, fixer. Subscriber

    Messages:
    12,856
    Location:
    Duvall, Washington
    The Eight can be a tricky beast to work on.

    Some have tantalum caps at the end of the preamp section that get bad.

    The amp trimmers can go bad and tear up the amp. The adjustment procedure is complicated on those. I recommend NOT screwing around too much if you are not ready for repairing amps.

    I have never seen a relay protection system one, is yours that type? I'm thinking a dirty relay can cause noise but it sounds more like you have transistor issues as things warm up.

    I think the preamp has known trouble maker transistors.

    I have worked on a few of those and unless you find a tech with good vintage experience, it may be a hard road ahead.
     
  8. LBPete

    LBPete Rolling Along Subscriber

    Messages:
    11,485
    Location:
    Long Beach, CA
    The Eight is one of Sansui's finest receivers, well worth fixing. As has been mentioned, it is a handful to work on. It's superior build quality makes for a lot of disassembly to get access to various boards. A protection relay was added late in production around January 1972. Does yours have a relay?

    Please post the serial number for the database. Click on the link in my signature block.

    - Pete
     
  9. VINTAGEO

    VINTAGEO Newbie in New B. Subscriber

    Messages:
    1,353
    Location:
    NB Canada
    20171215_175419.jpg image-20171216_131347.jpg 20171215_175443.jpg I just picked one of these beauties up last night in pristine shape in and out. Looks are deceiving, upon trying it out I found that the left channel is very crackly and weak, I'm guessing transistors as well.
    I notice some small transistors from the top on the sides down deep, that 1 has been replaced with one I haven't seen, the channel works ok so I'm assuming other side has failed.
     
    Last edited: Dec 16, 2017
  10. jeff's eight

    jeff's eight Member

    Messages:
    75
    Location:
    Phoenician
    Sansui Eight,221110514,JeffsEight
     

    Attached Files:

  11. VINTAGEO

    VINTAGEO Newbie in New B. Subscriber

    Messages:
    1,353
    Location:
    NB Canada
    I checked over the receiver and found 1 of the internal 5A fuses was blown, I replaced with a 2A to not inflict damage, and it's been working fine since..Is this a common fix?
     

     

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  12. stereofun

    stereofun Super Member

    Messages:
    1,233
    Location:
    Tucson, AZ
    Hi Vintaged, Yes that fuse, even if just one out of two missing, will severely distort that channel to weak output and severe crackle. I would not call the replacement fuse a fix per say, but rather pay attention to what might have triggered the bad fuse in the first place.

    If you want specific guidance on that you are better off starting a separate thread, so that we don't mix your Eight with the OP's - also for common courtesy. Cheers!
     
    Hyperion and VINTAGEO like this.
  13. jeff's eight

    jeff's eight Member

    Messages:
    75
    Location:
    Phoenician
    I retested the Sansui Eight and found the issue only to be on the Left Channel.
    I also ran out of the Eights amp to another preamp and the issue was unchanged.
    The Mac guy who worked on it before is going to look at it again today.
    I will pass on all the suggestions regarding transistors, fuses etc to him.

    Thanks!
     
    VINTAGEO likes this.
  14. jeff's eight

    jeff's eight Member

    Messages:
    75
    Location:
    Phoenician
    Repair guy found a blown fuse!
     
  15. dr*audio

    dr*audio Fish fingers and custard! Subscriber

    Messages:
    18,688
    Location:
    Cleveland, Ohio
    Took him that long to find it? He's a pretty fart smeller.
     
    Hyperion likes this.
  16. jeff's eight

    jeff's eight Member

    Messages:
    75
    Location:
    Phoenician
    I tried my magic for a while first.
     
    VINTAGEO likes this.

     

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  17. VINTAGEO

    VINTAGEO Newbie in New B. Subscriber

    Messages:
    1,353
    Location:
    NB Canada
    IMGP5170.JPG So I'm assuming it's working now?
    Someone pointed this out to me, remove the transistor covers, looks so cool!!
     
    Last edited: Feb 15, 2018

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