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Sony KV-27EXR15 drop out

Discussion in 'Electronic Repair' started by Darmok, May 30, 2005.

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  1. Darmok

    Darmok Guest

    Hi all,

    I have a 15 year old Sony KV-27EXR15 TV. Been a super TV for me for
    15 years.

    For the past couple years, when I first power it up (cold), the video
    flashes on and off about 5 times before it stabilizes and stays on.
    Its not much of a wait .. probably 15 seconds or less, but could be an
    indication that the tube is starting to fail ???

    The main problem which has just surface in the past few days, is that
    after having the TV on for a long time (say 5 to 15 hours), the
    picture and sound will suddenly drop out. From the sounds coming from
    the set, it sounds as though the set has been turn off, but pressing
    the power button does activate the relay, and it clunks in and out
    fine. For now, I push the power button so that I hear it go to the
    OFF position, and wait 2 or 3 minutes. When I power it up again, the
    set works fine, for hours ... maybe even the rest of the day.
    However, the problem has resurfaced many times, so I know its not
    going away by itself. I'm speculating that their could be a micro
    fracture in either a solder joint or the PCB around the main power,
    which is opening and causing the set to act like the power's been
    turned off. After a short "rest period", the set cools and continuity
    is restored ... for some random period of time.

    I've not been into the back of this TV in the 15 years I've owned it.
    My only other experience in fixing TVs was to replace a cap in the
    start up circuit of my 25 year old Sony 19"TV (still working great,
    but over-scanning), and removing and re-doing every solder joint in
    the tuner of my Sony 13" portable TV (it now is working fine and is 14
    years old).

    I did a Google search for this problem on the KV-27EXR15 and didn't
    come up with an answer. A couple people mentioned the blinking video
    at cold start up, and on person suggested the Pic Tube was weakening,
    whilst another thought it might be a bad solder joint.

    I've been extremely happy and fortunate to have 3 Sony's, all of which
    have given me good service, particularly the 25 year old 19" model.

    Any thoughtful insites would be appreciated ...

    Bill

    < cooncat at gmail dot com >
     
  2. Rono

    Rono Guest

    The flashing is a weak picture tube. You may be able to adjust
    the G2 (black potentiometer), on the CRT board. You may likely
    have bad solder connections at the horizontal drive transformer.
    Also replace the polarized capacitor in the horizontal drive. The
    last two items will cause the problem you are posting, & it will
    soon "blow up" the power supply. Rono.
     
  3. Darmok

    Darmok Guest

    Thanks for the tips ... I'll give it a look. Its too bad they don't
    include schematics with TVs ... my 25 yr. old 19" Sony had full
    schematics that came with it. The newer Sony with the problem doesn't
    have any schematics. However, I suspect that it will look similar to
    the 13" model that I have been into, i.e., a mainboard and a few
    daughter boards. We'll give it a look and see what we can see.

    BTW, is there any way to correct the over-scanning on the 25 yr old
    Sony 19" model? There are no Horizontal/Vertical size pots on the
    front of the set. Perhaps there are some inside .. I do have the
    schematics for this one, so perhaps I'll find my answer there.

    Thanks again,

    Bill
     
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