Sansui 5000A - Dim bulb tester stays bright - Please help

Discussion in 'Exclusively Sansui' started by TubeJunkie, Jan 11, 2019.

  1. TubeJunkie

    TubeJunkie Master of None Subscriber

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    Location:
    TN
    Hi. I have a Sansui 5000a that has a power issue. When powered on through my dim bulb tester, the light bulb stays bright, indicating problems. But when I remove the two speaker fuses, and power on with dim bulb tester, the Sansui powers on, and DBT, bulb dims, which is good. So I’ve went over the Ripple board, all good there. Pulled output transistors, they test good. Check diodes. So, I now will look at the Driver boards. Am I going in the right direction?

    This 5000a has the notorious F-1040 driver boards. Ugh... lol.

    Also, two of the big 2200uf filter caps measure more than double spec. Each Like 4800uf. That measurement taken with caps connect in circuit . The other two measure fairly close to spec.
     

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  2. Ylli

    Ylli Member

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    I don't see any speaker fuses on the schematic I found. There are two 4A fuses in the power supply, F002, and F003. These feed power to the left and right amplifiers respectively. First thing to do is to determine whether removing F002 or F003 improves the behavior of the DBT. That will tell you if the problem is in the right or left channel (or both).

    The schematic I have show these as 1500 uF. They are electrically in parallel and therefore will measure 2X in circuit.
     
    Last edited: Jan 11, 2019
  3. tom3

    tom3 Super Member

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    So. Ohio
    One way I've tested the amps is to use a night light as a dim bulb tester for each of the amps. Hook the light up to replace the R or L fuse. If the 7 watt bulb glows pretty bright you probably have a short in there. The circuit sees 80v DC so the bulb will glow some with a high current flow. Usually if there actually is a problem you'll see a blown fuse though.
     
  4. slimecity

    slimecity Super Member

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    You will get more help posting this in the Sansui section
     
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  5. TubeJunkie

    TubeJunkie Master of None Subscriber

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    I removed just the left 4a fuse and dbt is still bright. I replaced the left fuse, and removed the right fuse, dbt dims and receiver powers up. So, I’m assuming this tells me the problem is in the right amp? Looking at the receiver from the front, is the right amp board (F-1040-1) on the right?
     
  6. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    People who can answer that question 'off the top of their heads' mostly reside in the 'Exclusively Sansui' sub forum here on AK.

    Report your own first post (using the 'Report' link on the bottom left) - and request that this thread be moved there. ;)

    You'll get more frequent responses there, and anyone else who has this problem, and is looking in the right place i.e. the Exclusively Sansui sub forum, will see how it is solved. :)
     
    Last edited: Jan 13, 2019 at 10:54 AM

     

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  7. TubeJunkie

    TubeJunkie Master of None Subscriber

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    I’ve reported the request to move it to Sansui only section. Thanks
     
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  8. TubeJunkie

    TubeJunkie Master of None Subscriber

    Messages:
    338
    Location:
    TN
    I removed just the left 4a fuse and dbt is still bright. I replaced the left fuse, and removed the right fuse, dbt dims and receiver powers up. So, I’m assuming this tells me the problem is in the right amp? Looking at the receiver from the front, is the right amp board (F-1040-1) on the right?
     
  9. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Darn it - I thought the 5000 series experts would be swarming around - however nothing but ...... tumbleweed.......

    Bump! :)
     
  10. TubeJunkie

    TubeJunkie Master of None Subscriber

    Messages:
    338
    Location:
    TN
    Me too. I need some expert advice. I’ve been all over this thing and can’t find a bad component anywhere.
     
  11. s-petersen

    s-petersen Scott Subscriber

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    Middletown,New York
    Not really a Sansui or solid state guy, but I would remove the output transistors on the bad side, and see if it powers up, possibly a bad cap is throwing the bias off.
    If it still has a high current problem with those removed, try removing the drivers.
     

     

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  12. blhagstrom

    blhagstrom Mad Scientist, fixer. Subscriber

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    The 5000A F1040 boards are known problematic.

    There is a thread around here, either the 5000 or the 5000A that details a nice rebuild of the board.

    Find that thread.
    Study it.
    Pull the F1040 and rebuild them according to the info.
    Reinstall, test, adjust.

    Enjoy.
     
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