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Philips 41JP20 dead

Discussion in 'Electronic Repair' started by James Sweet, Feb 20, 2004.

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  1. James Sweet

    James Sweet Guest

    Still have this Philips 41JP20 awaiting my attention, replaced the BUW12A
    and HOT but the power supply still doesn't fire up, just makes a faint buzz
    then the relay clicks again and the orange and red LED's come on too.
    Standby voltage is there, not even a peep out of the other outputs. Any
    insight as to why the power supply isn't starting up? I thought I checked
    all the semi's but maybe I missed something.
     
  2. Jason D.

    Jason D. Guest

    What about resistors, caps? This can stop the whole show.
    Also philips used neon blue caps, they go bad.

    I'm not famillar with this philips chassis, what kind of this SMPS
    topology? One for standby only, one for main run power? Or same SMPS
    for both standby & run? Or uses regular standby transformer to power
    micro in turn trips the SMPS to run when commanded to turn on?

    Cheers,

    Wizard
     
  3. James Sweet

    James Sweet Guest

    I thought I checked all the lytics for ESR, replaced a few that were
    questionable. It uses a normal 60 hz transformer to provide the standby
    voltage.
     
  4. Bill Jr

    Bill Jr Guest

    James,
    Look for a 100uf 200 volt lytic near the relay and replace it.
    Also look for a 300k and 330 k resistor pair in series near the middle of
    the board.
    You could also be facing a bad flyback.

    Good Luck,
    Bill Jr
     
  5. BWL

    BWL Guest

    I have also seen a bad zener diode cause this; can't remember the location # at
    the moment; it's located in the "do not service" area of the P.S.
     
  6. Jason D.

    Jason D. Guest

    I'm not famillar with this philips chassis, what kind of this SMPS
    Better do that and see what you find by others whom suggested other
    things to check.

    Okay, A trick I use often because I've wearing hearing aids and can't
    hear flyback whistle or chirps of a SMPS so I used an scope probe
    laying along the core of the flyback or SMPS transformer core.

    This will instantly tell if your dog is trying to start SMPS part.
    This is unlike the recent JVC CRT TVs power topography, that one that
    states 105W, uses regular transformer for standby, very efficient SMPS
    & degaussing is juiced by the relay.

    Cheers,

    Wizard (deaf guy but can hear things generally with hearing aids but
    not all of freq ranges.)
     
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