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CRT monitor vertical deflection problem

Discussion in 'Electronic Repair' started by G B, Feb 6, 2010.

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  1. G B

    G B Guest

    I have a TLC 14001 NTSC monitor that has a vertical deflection problem. The
    horizontal deflection is working fine. The display starts 2/3 down the
    display and continues off the bottom of the display. I have probed B+, 14+
    and 14-, and all appear solid. I found a STV9302A vertical deflection
    amplifier and I have probed the input signal. (Pin 1). I expected to find a
    ramp waveform, but instead I see something that looks like:
    ----____ ----____
    --- | ----------------------
    ------
    | | | |
    | | | |
    |__-- | __---


    I followed the input signal back to a TCL-A32V02-TO (8852CSNG5PF4) 64 pin
    ASIC. It appears to be manufactured by Toshiba due to the 885xC part number
    (I am guessing). I removed the resistor between the pin on the ASIC and the
    vertical deflection amp inp to isolate it. When I probed it, it still had
    roughly the same shape as above maybe without the bounce after the edges.

    So questions... does anyone have any information on the above ASIC? Should
    the signal that drives the 9302 be a ramp? I assume it should be a 16msec
    period. If it does make a ramp, does it use an external cap to act as a
    integrator make the above signal? Does anyone know of a similar ASIC/TV
    that might give me clues? Am I even in the right area? So many questions..
    so little info.

    Thanks in advance,
    Greg
     
  2. Franc Zabkar

    Franc Zabkar Guest

    I can't make out your ASCII art. Try using a fixed width font such as
    Courier New.
    The applications in the datasheet all show sawtooth inputs.

    http://forums.futura-sciences.com/a...225292469-television-dalco-panne-stv9302a.pdf

    http://jp.ic-on-line.cn/IOL/datasheet/stv9302a_382931.pdf


    - Franc Zabkar
     
  3. Franc Zabkar

    Franc Zabkar Guest

    AFAICT, pin 7 adjusts the vertical position. Is its DC level around
    0V?

    There should be a low ohm resistor (eg 1 ohm) at the bottom end of the
    yoke circuit. The voltage across this resistor should be proportional
    to the vertical deflection current, ie it should be a sawtooth.

    - Franc Zabkar
     
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