Sansui 990 receiver protector flashing red.

Discussion in 'Exclusively Sansui' started by tonyanderson, Nov 3, 2017.

  1. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,005
    Location:
    Calgary, Alberta
    Does the unit come out of protection with the board pulled out,?? Maybe your bias is set too high.... Are you testing with a DBT for safety?? I would hook it up to a dim bulb tester and see what happens to the bulb. Also check the speaker outputs for a dcv measurement, should read in millivolts DC...
    If you find something in the neighborhood of 30dcv then we got a different problem me thinks..
     
  2. tonyanderson

    tonyanderson New Member

    Messages:
    10
    Yes unit comes out of protection with driver board out. Can't check or set bias if it won't come out of protection except with driveroard out.
     
  3. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,005
    Location:
    Calgary, Alberta
    Ok, right... Are you on a dbt?
     
  4. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,005
    Location:
    Calgary, Alberta
    I would take a multimeter and check for DC voltage at the speakers first off, then if you are only reading low DC there , I would pull the driver board out and minimize the bias pots. Use your dmm set to measure ohms, and verify the direction you turn the pot so you do not accidentally set them full blast!! After you have confirmed the bias pots are both minimized, plug the board back in and test.... Use a dbt!
     
  5. tonyanderson

    tonyanderson New Member

    Messages:
    10
    Don't have a dbt if that is a dim bulb tester.i have a multimeter. You can't check dc volts at the speaker outs if won't come out of protection or can I ? And you can't check dc volts at speaker outs or set bias with driver board out and receiver on or can I ?
     
  6. LBPete

    LBPete Rolling Along Subscriber

    Messages:
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    Location:
    Long Beach, CA
    You can't check DC offset at the speaker terminals if it's in protection. You need to have the driver board installed and there is really no reason to do that if it just smoked a bunch of resistors. It's likely you have blown output transistor. You need to check that first. A dim bulb tester is really good idea in your situation. Google it, there are lots of tutorials on line on how to build one.

    Your driver board is an early production board. Your 9090 was built before the production change to the power supply and driver board.

    For reference, to check the DC offset when this unit is in protection, set the unit on it's side, transformer side down and take off the bottom cover. There is a blue and a gray wire coming off the bottom of the power supply board. They go to the protection board. These carry the audio signal to the protection relay. Measure the DC voltage from each of these wires to chassis ground.

    - Pete
     
  7. nosirrah

    nosirrah Moderator Moderator

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    As earlier stated in your thread make a dim bulb tester. easy deal
     
    The Fuxtor likes this.
  8. eiraved

    eiraved AK Subscriber Subscriber

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    Antelope Valley, CA

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