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Pioneer rear projection tv: convergence or deflection?

Discussion in 'Electronic Repair' started by dstromb, Feb 14, 2005.

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  1. dstromb

    dstromb Guest

    I recently picked up, on the cheap, a Pro-98 Pioneer rear projection T
    whose picture is collapsed over roughly the top half of the screen
    down to the middle. In case that description doesn't make sense,
    picture is here (just snow, nothing hooked to tuner):

    http://209.234.77.62/tmp/pro98_raster.jpg

    There are no visibly obvious problems on the deflection or convergenc
    boards; I did touch up some suspect-looking solder points on bot
    boards to no effect. I don't have a schematic (yet anyway) but th
    voltages at the test points I can find are about right. The guy
    bought it from said it had failed in "exactly the same way" onc
    before, and a Pioneer dealer had replaced a board, he didn't know whic
    one. I did notice that on the convergence board, the large IC (STK4277
    looked like it had been soldered in by hand, so I assume that's what th
    dealer really did. But when people say things have failed "exactly th
    same way" before, that isn't always true - sometimes they don't reall
    remember what it looked like, they just remember it was wrong. So it'
    hard to trust that.

    Based on some other reading suggesting that STK4277 chip commonl
    fails, I've ordered one - they can be had for under $20 - but the mor
    I look at the symptom, the harder it is for me to believe tha
    convergence has anything to do with making half the picture go that fa
    out of whack, and there must be something wrong on the deflectio
    board.

    When the chip arrives later this week, I'll know whether the firs
    impulse was right, but does anyone recognize the symptom
     
  2. Doug

    Doug Guest

    Check all the large resistors for opens, and look on the same board for
    STK4274. It is the vertical IC and can cause your collapse. It looks
    like you probably do need the convergence chip, too. Good Luck!

    Doug
     
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