Sansui AU-5500 weak channel

Discussion in 'Exclusively Sansui' started by 2020, Aug 12, 2018.

  1. 2020

    2020 Active Member

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    I have a Sansui AU-5500 with the problem noted above. I hooked up a CD player through the tuner section and set up some speakers. One channel plays great, but the other is VERY weak.

    To try to isolate the issue, I tried different (working) speakers/wiring, then tried the other speaker outputs. The problem persisted. Tried changing the switch on the back separating the amp and preamp. Tried a different input (aux), listened though the headphone connection. Same results.

    Thinking it might be a dirty pot or elsewhere in the preamp , I hooked up a different (working) preamp through the AU-5500 amp section. Same result.

    I a baffled. Apparently there must be a flaw in my logic, so I thought I would asked for some input from this group. I am not a technician and have not opened up the case.

    Ideas or advice?

    Thanks in advance for any light you can share on this.
     

     

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  2. avionic

    avionic " Black Knights " Subscriber

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    May have a fouled protect relay contacts.
    Try tapping on the relay and listen for audible changes.
     
    Last edited: Aug 12, 2018
  3. avionic

    avionic " Black Knights " Subscriber

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  4. 2020

    2020 Active Member

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    Hmmm... tht sounds like it's worth a try.
    Thanks!
     
  5. slimecity

    slimecity Super Member

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    Yes try troubleshooting for the relay first.

    Sounds like you havent yet tried testing the pre and power stages separately?

    Plug a music source (at very low output level) directly into the main in RCA sockets. Turn up volume very carefully. Same result?

    Next get another amplifier - run a music source into your "aux" input on your Sansui - run RCA cables from the "pre out" RCA's of your sansui to any input on your other amplifier, turn the volume up - same result?
     
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  6. avionic

    avionic " Black Knights " Subscriber

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    Good point.
     

     

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  7. avionic

    avionic " Black Knights " Subscriber

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    Could just be a dirty switch or control in the pre-amp or function switching.
     
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  8. 2020

    2020 Active Member

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    Thanks much for the info.
    I did not express myself clearly in my wordy first paragraph.

    In fact, this is what bothers me: I tried bypassing the preamp section and running the cd player hooking through a different preamp into the AU5500 amp section only. So the AU5500 preamp was no longer in the chain.. still one weak channel. This caused me to deduce that the problem was probably in the amp section.

    I then tried bypassing the amp by running the cd player up to the AU5500 preamp. Then hooked up the AU5500 preamp to a different power amp. Still one weak channel.

    I tested the cd source and verified it is not the problem, changed speakers and speaker wires all to no avail. I even tried listening through headphones with the same result.

    Is the protect relay prior to both amp and preamp in the signal chain?

    Sorry to be a PITA.
     
  9. slimecity

    slimecity Super Member

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    Did you try swapping the RCA cable leads over?

    The relay is the very last thing in the chain before the amplifier speaker terminals.
     
  10. 2020

    2020 Active Member

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    144
    I think I am going to go back and double check the things I have done already.
    The things you guys have pointed out will help me find my way around.
    THANKS!
     
  11. BilboBaggins

    BilboBaggins AK Subscriber Subscriber

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    Yes, if you separate the amp and the preamp, and then crossover interconnects between pre and amp, if both the power and pre have a weak signal, you should see low output in both. I’m betting the low signal will change sides when you cross them. That would indicate the problem is in the preamp. If it stays on the same side, it is in the amplifier section. If both outputs are low, look for a problem in the power supply section. It has to be the common point for both amp and pre unless you have coincidence, which, incidentally, do occur.
     
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