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Samsung Projection HDTV Convergence Problems

Discussion in 'Electronic Repair' started by Chris F., Oct 31, 2009.

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  1. Chris F.

    Chris F. Guest

    This Samsumg set is clearly not going to be an easy fix. It came in with
    severe convergence problems - no two colors converged properly at any point
    on the screen. I started by checking the two large convergence IC's
    (STK392-010); both had the correct supply voltages, but two of the three
    sections on one IC were not functioning at all (input present but no output)
    so I assumed the IC was bad. For good measure, I replaced both IC's. Once
    powered up, the picture was still severely distorted but this time, ICZ103
    (which was formerly bad) now overheats severely. So I tried disconnecting
    the output leads from that IC, and it now runs cold - but of course the
    picture is still distorted.
    At this point I suspect an underlying fault somewhere else, putting an
    excessive load on the IC and causing it to fail. I checked the three yokes
    and all measure the exact same impedance, ruling out the possibility of a
    shorted yoke. Because of the complexity of this set, it would be pointless
    to venture any deeper without the aid of a service manual, or at least some
    advice as to what the problem might be.
    Thanks for any advice.
  2. May I ask a stupid question? Is there any possibility the "display elements"
    (tubes, LCD panels, whatever) are themselves misaligned? I assume they would
    be mounted and locked into a rigid frame, but... Is there any chance the
    owner is a screwdriver mechanic, and that a minor convergence problem
    tempted him into going where homo vulgaris is not supposed to tread?
  3. Chris F.

    Chris F. Guest

    There's no evidence that the static alignment was tampered with, or that the
    set was ever dropped etc. I will do some more checking and let you know.

  4. Disconnecting the output leads (presuming you mean the leads to the yokes)
    should not make the ICs run cold. Running them unloaded will usually cause
    overheating in the output resistors in the circuit. You may have
    disconnected the supply to the ICs.

    If you are getting correction from the DCU to the inputs of the output ICs,
    you probably missed something like an open resistor on the output stage.
    You may have blown a chip or a supply fuse.

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