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LF: Schematic for IPT LCD inverter (IPHS4L19)

Discussion in 'Electronic Repair' started by Dave Dunfield, Apr 19, 2007.

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  1. Looking for schematic or other technical information
    on an LCD power-supply./inverter made by IPT

    Model is IPHS4L19 REV 1.2

    This is from a Hansol/Multitech H950 monitor.

    Power supply portion appears OK, however when
    the inverter is activated, the backlights only flash
    briefly (By strobing the backlight control I can see
    that the image is being displayed). Looks like it's
    not oscillating at all after power-on, or is shutting
    down very quickly.

  2. James Sweet

    James Sweet Guest

    Schematics for this sort of thing are not available, they're considered
    replace-only devices. You're on your own I'm afraid, fortunately they're
    not very complex and can usually be repaired.

    Sometimes a bad tube will be detected and the unit will behave in that
    manner as well.
  3. Hi Dave, i've been repairing a few TFT monitors lately and i agree with
    James that service information on these units is very difficult to come
    across, You can spend hours Googling schematic sites to no avail.

    What i have found though is that these inverters seem to be very sensitive
    to imbalance between the performance of the TFT tubes. As the Inverters are
    usually feeding a pair of tubes (sometimes 2 pairs) a failing tube seems to
    cause an imbalance in the current drawn and the inverter chip will shut
    itself down.

    I keep a set of known good tubes and plug these in to the inverter,
    invariably these will remain lit indicating that the Inverter itself is ok
    and the fault is in a failing tube. If it is the Inverter thats at fault
    then, assuming you have a good drive signal from the inverter drive chip you
    should turn your attention to the main output transistors and transformers,
    look for blackened or burnt windings on the transformers as they do go s/c
    with alarming regularity.

    Good luck

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