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RCA projection TV Problem

Discussion in 'Electronic Repair' started by eganders, Apr 22, 2008.

  1. eganders

    eganders Guest

    My RCA rear projection TV has worked well after help from you TV
    service people in January, 2005. It has
    a chassis number of PTK195AC and is model P60812BL

    At that time I found that the surface of the PC boards had some of the
    coolent and other debris which I cleaned and that fixed the problem.

    Coming home from vacation today, the main fuse from the AC input
    failed. Upon replacing it, the convergence is all messed up. I went
    into the service mode using the front panel as the service manual
    describes, I can't seem to get the grid pattern that I got back in
    2005. Can anyone tell me

    1. What typically goes wrong when the main fuse blows and the picture
    goes out of adjustment

    2. How do you get into the built-in geometric alignment grid pattern?

    I am into the service mode, but it does not seem to have any pattern
    except the P:(for parameter) and V (for parameter value): on the
    screen.

    I would like to nurse this TV along for a while. It has given good
    service and I have no reason to replace it other than the present
    problem. I really don't want to get into it deeply. For example, I
    would prefer NOT to get a chipper checker or have to hook an
    oscilloscope to it.

    sci.electronics.repair
     
  2. eganders

    eganders Guest

    Here is a photo of what the convergence problem looks like

    http://img.photobucket.com/albums/v384/eganders/60inchConvergence100_1203.jpg
     
  3. eganders

    eganders Guest

    Here is a photo of the problem

    http://img.photobucket.com/albums/v384/eganders/60inchConvergence100_1203.jpg
     
  4. eganders

    eganders Guest

    OK...

    I checked the voltages out of J19701 connector from the power supply
    to the convergence board. They are not to specification (at all).

    pin 1 should be -45, is -1.8
    pin 2 should be -15, is -1.9
    pin 3 gnd
    pin 4 should be +23, is +23.3
    pin 5 should be +15, is 0
    pin 6 should be -45, is 1.7

    If the plug is pulled going to P19304, all the voltages go to 0 volts
    at J19701 on the power supply board. The service manual says to
    "disconnect power supply". I took that to mean pull J19701. I assume
    that the power board is bad. My question is..
    Was the board blown by the load of something wrong on the convergence
    board, or just a bad component. I checked the input diode bridge and
    it seems to be OK. I would guess I should replace the power supply
    board. I wonder how much that is? I would hate to blow it after
    changing it out. What are the chances of that?
     
  5. Mike S

    Mike S Guest

    The last thing you should do is replace the power supply board. There's a
    good chance something else in the TV may have caused a short or heavy load
    on the power supply, and the new one would be blown.
    Also it is very unlikely you could buy the board, or the price would be
    outrageous. It is possible your convergence amp circuit has failed, this
    should be tested/repaired first. Then the power supply should be
    troubleshot and repaired.
    Also, if you try to use adjustments in the service menu, or manual
    adjustment of any kind to converge the image, your results are likely to be
    very poor and unwatchable. Then when the TV is correctly repaired, it may
    take HOURS longer to realign all the settings you have changed. Those
    settings and/or adjustments are meant to fine-tune the picture when the
    circuit is working correctly.
     
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