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Panasonic TH-50PX80U Power Supply Mystery

Discussion in 'Electronic Repair' started by [email protected], Dec 18, 2013.

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  1. Guest

    Bought this set non-working a few weeks ago and thought it would be an easy fix. It would power up for a second, then shut down and blink an error code suggesting a problem with the SS board (7 blinks I think). Someone had clearly attempted to fix said board and had made a mess of it, but since everything else looked good I thought it should be an easy fix.
    I ordered a brand new SS board and installed it, and to my surprise the set was now totally dead - no lights at all. I checked a few voltages on thepower supply and soon found the standby 5V was missing. So I bought a service manual, only to discover that Panasonic no longer publishes schematics for any of its power supplies. It did however include a block diagram, and from that I was able to trace the 5VSTBY to Q151, used a switch by the power control CPU. Measured 5V on the input and the control side of Q151 (collector and base?) but no output. Tried jumping the transistor, the standby LED now lights but only to display a different error code (10 blinks - A board). Tempted to throw the set out in the snowbank at this point but back problems prevented me from doing so.
    So I thought I'd ask for some advice before wasting any more time or money on this. Note that it sat for about 3 weeks while I waited for the new SSboard to arrive, so maybe the set reached it's self-destruct point during that period (they DO self-destruct even when not in use, thanks to the lead-free solder you know).
    Thanks for any advice.
  2. Guest

    My own mistake, forgot to take a little jumper plug from the old SS board to the new one, an apparent safety feature of the set I guess. Now the set powers and stays on, but the screen is blank with no OSD, looks like issues with the mainboard. If it isn't one thing, it's another....
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