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Sony 27 in. KV-27S26

Discussion in 'Electronic Repair' started by Phil, Jul 17, 2004.

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  1. Phil

    Phil Guest

    Hello
    I have a Sony 27 in. Model KV-27S26 , lost everything , pulled Power Supply
    board out and found Cap. burned and Transistor Q601 with EBC welded together
    , used to have SAMS schematics at our local library but they did away with
    them, wonder if anyone has a drawing or could give me a ECG/NTE cross
    reference for Q601, this transistor drives a small transformer.
    Thanks
    Phil Lohiser
    W8KLK
     
  2. David

    David Guest

    1. There is no NTE cross for those.
    2. You have many more parts than just those two.
    3. Proper repair, that does not result in all the parts blowing up again,
    requires careful analysis of the SMPS waveform while bringing it up on a
    variac.
    4. Odds are good that the VDRs in circuit were damaged, and there is no way
    to test those, you have to replace them. Will result in all the new parts
    failing.
    5. Odds are also very good the transformer was damaged when the driver
    transistors failed. Again will result in lost parts and time.

    The best bet for success is to get a hold of Sony's multi page
    troubleshooting guide for the power supply for that specific chassis and use
    only Sony exact parts. Others will echo the same kind of sentiment with
    that specific power supply design. It will likely cost less in the long run
    to have a Sony experienced and trained tech repair this one for you, unless
    you have one available in person to help you through the supply.
    Just a schematic or service manual on late model Sony SMPS descrete design
    is not enough for someone who has not worked on Sony's SMPS design in the
    past, the troublshooting training information from Sony is an almost must
    have.

    David
     
  3. Phil

    Phil Guest

    Thanks for the interest in my Sony PS problem , and the thoughtful answer ,
    will get problem fixed , am thinking of purchasing a new Sony TV as I really
    do like the picture , am wondering if the same weakness is still with these
    units or has Sony corrected it.
    Thanks again
    Phil
     
  4. Jason D.

    Jason D. Guest

    This tell me more than this.

    Sony uses two matched transistors (Q601 and Q602) for SMPS. When
    something (secondary side loads) shorts out, this always will take
    those pair out and fry the 0.1 ohm resistor (as fuse).

    This means you do have either bad horizontal transistor (shorted)
    caused by solder fractures on the horizontal driver circuits and any
    horizontal circuits. Very rarely have vertical IC failure. While in
    there, resolder all the power resistors, heavy parts pins etc.

    I see this often in Sony sets and many electronic suppliers put
    together a rebuild kit for this. Get one from decent supplier and
    make sure this supplier is not using generic parts.

    Cheers,

    Wizard
     
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