Sansui 990 receiver protector flashing red.

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

  1. tonyanderson

    tonyanderson New Member

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    Help with my Sansui 990 receiver. Been sitting idle 25 years. Plulled it out powered up and protector flashes red. Someone told me to pull driver board and check fuseable resistors. Pulled the driver board out and powered up red red green came out of protection mode. Thought I was on to something. Checked the fuseable resistors and all five have no open circuits. What else can I check.
     
  2. tnsilver

    tnsilver Super Member

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    You should probably do these tests using a dim bulb tester. It's a lifesaver so look it up (DBT) and build one if you don't have one.
    Those fusibles should be in their spec'd resistance value. Not open is not enough. The protection circuit does it's work to eliminate
    too much DC current from reaching the speakers, so you should really follow the DC offset adjustment procedure in the manual.
    While at it, the bias current adjustment routine too.
     
  3. avionic

    avionic " Black Knights " Subscriber

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    Was it working 25 years ago. Before it was put in storage ?
     
  4. avionic

    avionic " Black Knights " Subscriber

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    As tnsilver said. Check DC offset. You might have a shorted output... DC offset check will point to the next step in T-shooting your suiy.
     
  5. tonyanderson

    tonyanderson New Member

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    Must have taken it out of service for a reason. Been stored 25 years But can't remember. Haven't tested output nor am sure I can with the ? With the driver board removed to keep from going in protection mode. Will recheck the fuseables to see if they are in spec.
     
  6. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

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    Nice unit! My bet are out of spec fusibles on that driver board.
     
  7. avionic

    avionic " Black Knights " Subscriber

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    No you can't.
     
  8. avionic

    avionic " Black Knights " Subscriber

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    Allow me to clarify -- Shorted output transistor(s)--
     
  9. avionic

    avionic " Black Knights " Subscriber

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    Be able to tell real quick if you have rail voltage present when you check the DC offset.
     
  10. LBPete

    LBPete Rolling Along Subscriber

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    tonyanderson, welcome to AudioKarma, Exclusively Sansui Forum. Odds are, all that is needed to get it out of protection is to replace those fuseable resistors. The classic failure mode of those resistors is exactly what has happened with this receiver. If it was in storage for 25 years, all the capacitors have lost their charge. The start up surge that occurs when first turned on to charge all those caps after long storage can cause the 40 year old fuseable resistors to go open. Start by replacing them with 1/2 watt metal film resistors. Then we can talk about cleaning all the controls.

    While you have it out, please post the serial number for the database. Click on the link in my signature block.

    - Pete
     
  11. eiraved

    eiraved AK Subscriber Subscriber

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  12. kevzep

    kevzep Its all about the Music Subscriber

    What LBPete said!! ^^^^^
     
  13. tonyanderson

    tonyanderson New Member

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    Ordered 10 resistors from Digakey didn't have the foil ones in stock so ordered the carbon ones. Hope that's ok. 2 10 ohm 1\2 w. 2 22 ohm 1\2 w 2 390 ohm 1\2 w and 4 4.7 ohm 1\2 w. Now we wait. Thanks LBPete.
     
  14. kevzep

    kevzep Its all about the Music Subscriber

    Metal film is what you should be using, not carbon comp although they will work.
    I find it hard to believe Digikey didn't have metal film resistors???
     
  15. tonyanderson

    tonyanderson New Member

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    Might have been looking at metal foil ?
     
  16. tonyanderson

    tonyanderson New Member

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    Will I have to check the DC volts and adjust bias on VR-1 Tru 4 ?
     
  17. tonyanderson

    tonyanderson New Member

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    Will I have to check the DC volts and adjust bias on VR-1 Tru 4 ?
     
  18. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

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    The resistors should be labelled "flameproof"
     
  19. tonyanderson

    tonyanderson New Member

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    Went back to Digikey and ordered the flame proof Vishay BC metal flim resistors. They were there just didn't see them the first time Thanks all.
     
  20. tonyanderson

    tonyanderson New Member

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    Replaced 10 fuseable resistors reinstalled driver board No go still flashing red. Pulled the driver board back out and checked as much as I could and noted at least 7 resistors with open links. ( not fuseable ones )Now what to do ? Do you guys think a driver transistor shorted out taking the resistors with it ? Do I just send the driver board in to get a recap of the driver board ? Or send the whole receiver in for recap/restore 575 plus shipping both ways.
     

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