Sansui 9090 (non db) power meter meter fault

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

  1. sajjad amer

    sajjad amer Active Member

    Messages:
    270
    Location:
    Lincolnshire, United Kingdom
    This receiver was rebuilt by me, using information on this forum last year. Everything was working fine till yesterday when suddenly left channel power meter has become "oversensitive" even at 1/4 volume it is hitting the maximum mark. Pressing meter button has no effect and swapping input leads has no effect either.

    Pressing the mute button does reduce the amplitude of needle movement but still movement is far more on the left meter. When the receiver is powered on and nothing is playing, both needles park at exactly the same place, right in the middle of the bold line on the extreme left side of the scale.

    Before posting, I have looked at this link,

    http://audiokarma.org/forums/index.php?threads/9090-vu-meter-adjustment.620904/

    however, it feels beyond my technical expertise. Am I correct in thinking that I can download a 1KHZ sound file and play it after attaching 8 ohm resistor across speaker terminal and adjust the trim pots on protection board. I am scared to blow the output transistors by putting a resistor across the speaker terminals.

    Also as the problem is of sudden onset, the problem is likely to be somewhere else and not the adjustment I feel and welcome any guidance as always.
     

     

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  2. Robisme

    Robisme Sansui Enthusiast Subscriber

    Messages:
    11,949
    Location:
    Martinez California
    So you're saying that you switch meter leads and the left meter still acts up being fed by the right meter wire? And you swap the wires at the meters?

    Then you have a bad meter.

    If the problem switches meters, then check the associated resistors and diodes in the meter circuit.

    Like R15 and R16. R23 and R24. And check the trimmers. You can try turning the trimmer back and forth to see if that helps. I have seen bad trimmers but they usually cause the meter to not respond.


    Rob
     
  3. dr*audio

    dr*audio Fish fingers and custard! Subscriber

    Messages:
    18,948
    Location:
    Cleveland, Ohio
    Try the meter adjustment first to see if it has any effect, Mark the original position of the trimpot.
     
  4. sajjad amer

    sajjad amer Active Member

    Messages:
    270
    Location:
    Lincolnshire, United Kingdom
    I am sorry for the late reply, but I had a motorbike accident and broken my wrist. So I will restart this project in 4 weeks when plaster comes off.
    I felt not replying to someone who is trying to help is rude, hence shared above information.
    Thanks
     
  5. DougBrewster

    DougBrewster AK Subscriber Subscriber

    Messages:
    553
    When you get back in business take a look at the resistor/diode chain R21/D11 (or R22/D12; I can't tell which is the left channel) on F-2547 to see if it's gone high or open which would produce the effect you are seeing.
     

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