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Philips 2b chassis and my mind sanity

Discussion in 'Electronic Repair' started by Emanuele Girlando, Mar 18, 2007.

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  1. Ahhhh! Help!
    Got a philips 2b TV set (actually a Pioneer sv-2103).
    Arrived with shorted HOT and a couple of (safe) resistors burned out.
    Replaced all of them and turned on the set through a "bulb limiter".
    SMPS seems working: 140V, +20 and-20 and +13V lines were all low
    (because of the bulb) but present and reasonable. Scoping primary and
    secondary sides of the SMPS gave me signals in good shape....
    But: no HT, no standby 5V. Signals in horizontal path were ugly.
    Replaced the LOPT. Now I have good shaped signals in the horizontal
    path, good signal @ HOT's collector, some HT, some filament current,
    some standby 5V.
    So I decided to go without series bulb. ... opss! Something is now
    tripping down the SMPS after few milliseconds.
    To better trace the problem I connected a bulb in place of the HOT:
    140V in perfect as they are +20 and -20 and 13V ... confirming the
    SMPS is properly working. Turning the 140V trimmer effectively
    regulates B+ as expected, letting me argue that the SMPS' regulator is
    also working properly .
    Suspecting something in the HOT circuit I replaced the two (damper?)
    diodes, the resonating cap, checked resistors .... without any
    Turning back to the series bulb arrangement, the circuit doesn't trip
    working as described before... but with further testing I noted that
    sometime the signal @ the HOT's collector is somehow irregular.
    Sometime it shows a third irregular swing in the middle of the main
    two.. -> checked EAST-WEST correction circuitry... it seems ok.....

    Ahhhh! HELP!!

  2. Has anybody out there suggestions about how to disable protections in
    the 2b chassis?
  3. Guest

    A Philiips 2b or not a 2b?

    Unfortunately no. My tv chassis knowledge is far too out of date. I
    did once replace the whole smps though, that got round all protection
    issues. Just used lightbulb dropper, rectify, smooth... But you cant
    do that sort of thing nowadays.

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