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Help identifying part on Sony KV-27EXR15

Discussion in 'Electronic Repair' started by Darmok, Aug 8, 2005.

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  1. Darmok

    Darmok Guest


    Some time ago, I mentioned that my 15 year old Sony KV-27EXR15 would
    periodically turn itself off. After some time, it would come back on,
    either by itself, or if I turned the set off from the front panel and
    let it sit for a while.

    Today, I took the time to go over all the boards closely. I was
    looking for fractured solder joints or traces and found none. All
    boards were in great shape!

    Well, I reassembled it, and turned it on, and might have stumbled on
    the cause of all this ... or at least an indicator of what part is

    On the "G" board, which is located on the left side of the chassis
    (looking into it from behind), there is a small, cubical black part in
    the lower left corner, with the following printed on it:


    Looking at the schematic for the KV-27EXR15, I find that this is a
    part called "THP607", a 3 legged part. This part gets VERY HOT when
    the set is on. When the set goes out, it cools off, and the set will
    power up again. I'm thinking that this is some kind of thermal
    protection device.

    Here are the questions:

    Is this part known to fail, and thus the likely cause of my problems?

    Is this part getting hot due to something else in the set drawing too
    much current (not likely, since neither of the two glass fuses have
    blown .. ever .. in 15 years!)

    Where would one find a replacement part like this to install?

    Thanks for any help you can provide ...

  2. Franc Zabkar

    Franc Zabkar Guest

    It's a PTC (positive temperature coefficient) resistor. It normally
    runs hot. When it does fail it takes out the main fuse. It is not the
    cause of your problems. It is used to provide a short pulse of current
    to the degaussing coil at switch-on.

    - Franc Zabkar
  3. sofie

    sofie Guest

    What you described is the posistor for the automatic degaussing circuit....
    and it is suppose to get hot. When you first turn on your television you
    will hear a whooshing noise... that is the degaussed working.... and when
    the posister heats up it gradually reduces the power going to the degaussing
    coils... then a relay will cut off all power to the degassing circuit. This
    is NOT the cause for your television turning itself off, it has absolutely
    nothing to do with your television's on/off operation other than degaussing.
    I would still suspect faulty solder connections or maybe a heat sensitive
    component in the other areas of circuitry, but in not the degaussing
    You may want to go to the website for this newsgroup at
    there, with some searching, you can learn a lot about the degaussing circuit
    and other things to look for in your quest to fix your television..... the
    answers are there if you plan to spend some quality search time.
  4. Darmok

    Darmok Guest

    Confirmed that this is a PTC. Sheesh ... that damn thing gets SO HOT
    that I can't even put a finger on it. Its a wonder the plastic case
    doesn't melt.

    Well, after more looking and reassembling, the set wouldn't even power
    up. So I pulled the G board out (again) and looked at it under my 3x
    magnifier light, and found 2 ICs with fractures in the lead solder.
    One was IC653 in a TO-220 case, and the other was an 8 or 9
    (staggered) lead IC that controls various voltages. I re-soldered
    both of those, put the board back in, and it fired right up. Now I
    have to see if those were the cause of it shutting itself down. Guess
    I'll just have to leave it on while I'm home to see if it will drop

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