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Philips PTV916 shutdown problem

Discussion in 'Electronic Repair' started by Andy Cuffe, Nov 10, 2004.

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  1. Andy Cuffe

    Andy Cuffe Guest

    I'm working on a Philips 60P8342 (P916 chassis) that shuts down about
    3 to 5 seconds after turn on. I have the electronic version of the
    service manual and so far everything I've checked looks good. The low
    voltage power supply is regulating correctly and it has horizontal and
    vertical deflection. I tried pulling the convergence plugs in case a
    convergence IC was shorted. I also pulled the CRT sockets in case one
    of the CRTs was shorted. It has high voltage until shutdown.

    The manual I have isn't very helpful in determining the cause of
    shutdown. Does anyone with experience on this chassis have any
    suggestions? At this point I would be happy to take the risk of
    disabling the shutdown circuit to see what happens. If it can't be
    repaired inexpensively and quickly it will be scrapped anyway.
    Andy Cuffe
     
  2. John Del

    John Del Guest

    Subject: Philips PTV916 shutdown problem
    I have the electronic version of the
    Wow, if you can get Philips e-manuals to run, you're way ahead of me. But I'll
    offer some advice anyway.

    Check any secondaries off the HV transformer. If the voltages appear in the
    normal range before shutdown, I would defeat the shutdown circuit (you already
    confirmed vert and horiz deflection, so it should be safe to do if the HV isn't
    too high).

    I try to avoid all Philips projectors, but I have seen the splitter cause this
    when the internal feedback divider goes off value.

    John Del
    Wolcott, CT

    "I'm just trying to get into heaven, I'm not running for Jesus!"
    Homer Simpson

    (remove S for email reply)
     
  3. Andy Cuffe

    Andy Cuffe Guest


    I have a little more information on this set. The boss decided to
    order the complete deflection/HV/power supply board which arrived
    yesterday. The HV splitter is built into the flyback. I installed it
    and the same problem is still there. This leaves the
    control/video/convergence board in question. I was able to cycle it
    back on several times quickly enough for the CRTs to warm up. I can
    see 3 blank dim rasters with retrace lines. Deflection looks normal
    and they were in focus. The voltages to the CRT boards are normal.
    It looks like a possible video problem. For some reason it takes mugh
    longer to shut down after the set has been off for a while.

    I agree that Philips projectors are to be avoided at all costs.
    Andy Cuffe
     
  4. Ol' Duffer

    Ol' Duffer Guest

    Do you get a blinking power LED?
    If so, it will blink the error code.

    Most common I have seen is error 2, which is
    supposed to be vertical sweep failure, but usually
    the problem is not in the vertical sweep, but in
    the circuits that detect the presence of sweep.

    If I am thinking of the right chassis, I have only
    seen one with an actual large signal failure, and
    the rest have all been flaky SSB boards. This is
    the little board in the SIMM socket near the right
    side of the set. In the case of the alleged error 2,
    it has been a shorted input pin on the microprocessor,
    the pin that receives the vertical pulse. These
    little boards, which are the brains of the set, seem
    to be chronic failure items. Of course there are
    some SMD resistors, capacitors, and a transistor
    that "condition" the signal before feeding it to
    the SSB, but the signal path seems to always be okay.
    And of course, the SSB is hard to get at and diagnose.

    IIRC, there is a PC software and interface package
    available to diagnose these new chassis. Like anyone
    can afford such a thing in this day of disposable
    TV's. Maybe the factory has one. Good luck!
     
  5. Andy Cuffe

    Andy Cuffe Guest

    That sounds like the chassis I'm working on. I will check on the
    error code next time I work on it. Thanks for the tip.
    Andy Cuffe
     
  6. Andy Cuffe

    Andy Cuffe Guest

    You were right. A new SSB board fixed the problem.

    Andy Cuffe
     
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