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Toshiba 32" model 32A10

Discussion in 'Hobby Electronics' started by [email protected], Jan 10, 2008.

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  1. Guest

    I have a 32" Toshiba that displays a picture, but the on screen
    display of the selected channel, volume, or menu item when menu is
    selected does not appear. I have successfully followed the procedure
    for initializing the registers in the QA02 processor but still no
    display. Any ideas?

    Bob
     
  2. Guest

    Update:

    Found a block diagram of the Toshiba TMPA8700CPN micro proc (QA01 in
    the schematic). It produces the On Screen Display found in the TV.
    Pins 31 &32 have a 8MHz oscillator attached that is functioning. Pins
    28 & 29 are connected to LB01, a TRF1196D IF Coil. I do not see this
    oscillator functioning. Anyone out there know what the characteristic
    of the TRF1196D coil are? (DC resistance?). Additionally, would anyone
    know what frequency this oscillator is supposed to run at?

    It would be my conclusion that either the TMPA8700CPN micro proc
    (Toshiba part number 23000287) or the TRF1196D IF Coil (Toshiba part
    number 23262280) would be the issue. I have removed both parts and
    cleaned the circuit board to remove any residue that might cause this
    high impedance circuit to malfunction.

    If any of you out there are interested, I have the schematic diagrams,
    etc. and could email them .

    Any help would be appreciated!

    Cheers from Canada!

    Bob
     
  3. TOH

    TOH Guest


    Final Update:

    TMPA8700CPN data sheet input output circuitry section revealed that
    the oscillator is gated and that was why it was not observed to be
    working. When a button is depressed, the osc. starts and runs for the
    duration of the display. I observed a frequency of about 1KHz.
    Assuming this was the dot clock for the display, the frequency should
    be at least 8 dots/char X 32 char/scan line X 15,750 scan rate =
    4,032,000Hz. The osc. must actually run faster because of the
    requirement for margins on the left and right sides of the display as
    well as retrace time.

    I once again removed the TRD1196D coil.. Its DC resistance measured
    about 860K. I decided to mechanically open up the part and see what
    was inside. I found that the measured DC resistance was the result of
    pollution inside the part and the coil itself was open. Using my fine
    tip soldering iron and my magnifying lens, I managed to restore the
    connections. DC resistance turns out to be less than 1 ohm.

    The Oscillator now runs at 5.7Mhz and the display works fine. The osc.
    is gated by the horizontal sync signal to avoid jitter.

    Bob
     
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