Sansui AU-D9/left channel out

Discussion in 'Exclusively Sansui' started by jkcoondog3, Dec 27, 2012.

  1. jkcoondog3

    jkcoondog3 Active Member

    Messages:
    277
    Hello and good morning. I just picked up a Sansui AU-D9 Amp at a local GW and after hooking it up I find that their is no output (sound) to left channel. Where do I start? My first guess is bad output transistors, 2SA1169, 2SC2773. Where do I find these? NTE has Substitutions or replacments NTE 92, and NTE93. Would that work? If so, do I need to replace all of them(left and right channels), or just the bad transistor? Any help would be appreciated. thanks
     
  2. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    You are making a huge assumption about the output transistors - how about getting some DeOxit and clean the switches first?

    BTW: Do not use NTE replacements for the transistors - even if it was a last resort - and even then don't use them, the AU-D9 deserves better.

    Did I mention not using NTE replacements ?
     
  3. ConradH

    ConradH AK Subscriber Subscriber

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    You start with a thorough visual inspection- bright lights & magnifying glass. Look for caps with broken blowouts, bulges, cracked resistors, broken wires and anything else that might be physically evident. Next, you start probing with your DVM on "diode check", testing all diodes and transistors. You need to know how to test both NPN and PNP transistors and be confident of the results. None of this is done with power on! Report back with findings.
     
  4. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Yes, this ^^^ :yes: much better as a first step.
     
    Last edited: Dec 27, 2012
  5. jkcoondog3

    jkcoondog3 Active Member

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    277
    I did a good de-oxit job on all the pots, but that didn't help. Whats wrong with NTE? What other replacements are there and where do I find them. Surely someone has had to replace them with a substitution.
     
  6. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    But not NTE.

    It is my understanding that NTE devices are just labelled up with an NTE number if they approximately match up to a basic spec. So you can get half a dozen devices all called NTExxx which could have been originally made as different devices, but just labelled the same by NTE because they meet the basic spec, do you want unmatched output transistors in your AU-D9 ? :no:

    Look here and check out post #13
    http://www.audiokarma.org/forums/showthread.php?t=98065&highlight=2sa1169+2sc2773
     
    Last edited: Dec 28, 2012
  7. Robisme

    Robisme Sansui Enthusiast Subscriber

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    11,402
    Location:
    Martinez California
    NTE gets a bad rap. You can buy matched pairs.

    I have used them in a pinch, and they have never let me down.

    While they may meet the minimum spec, when you cross them, the ones that cross usually have higher ratings than the original. That's because one may cross to many.

    That said, they are a last resort, but better than counterfeits.:yes:

    Do you have a way to test the preamp feed to the driver board? That would tell you if the problem is in the preamp or amp.

    Check the signal at the relay, or tap the relay. It could be bad.

    I have one open here, so if you have any questions about measurements and what not, let me know.

    Rob
     
  8. jkcoondog3

    jkcoondog3 Active Member

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    277
    I don't quite understand. I don't have a preamp with it, but I did use a tuner with the amp and left channel no workie. Thanks for your help Rob, you always seem to chime in on a lot of the issues I have with different receivers.
     
  9. Robisme

    Robisme Sansui Enthusiast Subscriber

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    Location:
    Martinez California
    I mean the built in preamp of the amp. See the pics below. See the red and yellow wires that feed the amp board? The yellow is for the left channel.

    If you have a way to check the signal at that point, it will let you know if the problem is in the preamp section of the AU-D9 or the amp section.

    If you have signal at that point, the preamp section is good.

    The relay is hard to get to. It's on the board by the speaker terminals.

    [​IMG]

    [​IMG]

    Rob
     
  10. jkcoondog3

    jkcoondog3 Active Member

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    277
    I am assuming that I check the yellow wire with a digital volt meter while the unit is on? Do I set the volt meter to DC? I only see 1 fuse. Other units I've dealt with have several more. Is that the only fuse this unit has?
     
  11. DCinDC

    DCinDC I'm here to fix it

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    :popcorn:
     
  12. Robisme

    Robisme Sansui Enthusiast Subscriber

    Messages:
    11,402
    Location:
    Martinez California
    A scope or signal tracer would be the best way to check it, but you could check it with a meter.

    Set the meter for AC and connect the black lead to the chassis and the red lead to the conductor of the yellow wire that is closest to the center of the board. It should have white insulation on it.

    With the speakers disconnected or the speaker selector set to off, play a source through the Aux inputs and take a measurement with the volume at 12 o'clock.

    You should see a fluctuating voltage between .001 VAC and .060 VAC.

    Compare it to the other channel and see how it looks.

    If both channels look the same, the preamp is probably OK.

    Have you tried B speaker outputs yet? They use a different relay.

    Rob
     
  13. jkcoondog3

    jkcoondog3 Active Member

    Messages:
    277
    I'll try all that the next time I mess around with it. Yes the B channel works, but only on the R channel, no left on either A or B. I also taped the relay and nothing happened there either. I did a thorough inspection on all the caps and wires, etc, and I find nothing that would create an issue. I am no techie by any means and have very little knowledge on using and testing components. I can certainly tell a bad cap or or wire not connected, and i can solder but that is about the extent of my capabilities. Btw I did purchase some Nte transistors because they had them at the local Frys electronics. I removed the old ones on the left channel and replaced with NTE and still no left channel output. I then put the originals back in.
     
  14. jkcoondog3

    jkcoondog3 Active Member

    Messages:
    277
    2 relays?

    Are you saying it has 2 relays. 1 for A and 1 for B? I only noticed 1 on the upright board near the speaker terminals.
     
  15. getter365

    getter365 H.H. SCOTT stereomaster

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    Location:
    North Babylon, NY
    Hi there,

    Yes, before replacing the output transistors, clean all of the switches with De-Oxit and make sure the relays are working good - assuming the AU-D9 has relays. I owned a AU-D7 and I now own a AU-D5. So maybe the speaker relays could be bad. Good luck - hope you get that amp working in all of its glory.
     
  16. Robisme

    Robisme Sansui Enthusiast Subscriber

    Messages:
    11,402
    Location:
    Martinez California
    There are three relays. One for A speakers, one for B speakers, and one for the headphone output.

    If the left channel is out on all (A,B,headphones) outputs, then I doubt it's a relay problem.

    You could have pulled the outputs and tested them instead of replacing them.
    Or, swapped right channel with left channel.

    You really need to test the input to the amp board as suggested to determine if the preamp or amp is the problem. It will eliminate some unnecessary work.

    Rob
     
  17. Hotsupply

    Hotsupply New Member

    Messages:
    3
    Guys i know this thread is ancient but i have same problem too. have this problem solve? yesterday i am messing with additional preamp and suddently i lost my left channel (A and B, headphones yet to test) in my AU D9. Wishes to know the issues and solution.

    From the explanation above, relay may not be the issue. i try to find the fuse. but only one fuse found (which in good shape). love this amp

    upload_2017-6-15_9-7-25.png
     
  18. j_loop

    j_loop AK Subscriber Subscriber

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    Location:
    SW CT
    Is the channel dead throughout all inputs or just one?

    And let's not forget the healing power or reflowing solder joints...
     
    Hotsupply likes this.
  19. Hotsupply

    Hotsupply New Member

    Messages:
    3
    As my source is just one...and it is from pre amp..try changing the input result the same fault....i try figuring out the connection...changing the cable yesterday..and it appear that my cable from preamp to the input is the culprit...left rca cable are not function...replace the rca and it all good....thanks for your help anyway..
     
  20. AnthonyL

    AnthonyL New Member

    Messages:
    23
    That's the easiest problem to solve! Congrats. For the future, one great way to find these issues is to do trace the audiopath with an audio probe. Use a small amp and cheap speaker that you don't care about, and use the test probes from your multi-meter. That's your audio probe. Set volume on low. Aligator clip 1 input lead to ground. Then use the probe to trade the signal path, starting with the input RCA, through the pre-amp boards and audio controls until you find the point where the signal drops. Reflow the solder in the joints leading up to and after that point, then test again. If that doesn't work, replace the component.

    This approach is very fast, and also gives you an idea of what each PCB component is doing to the signal.
     

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