DashFest JJ's life and project dumping grounds…

15Aug/090

The Thrift Store 50 Inch Plasma

So I was at the DI last weekend.  I stumbled apon this:

A Panasonic TH-50PHW3U   50" 720p Plasma, for $100.  Original MSRP $9670 in 2003!

At this price, it obviously didnt work.  It turned on for about 4 seconds, then shut off with the power LED flashing red.  On the chassis a repair estimate/bill was attached.  It had a couple of part numbers listed, and scribbled on was the note "Panel est. declined".  Cost of repair, $978.84.  The entire time "bad capacitors!" is running through my head.  I lug it home, and immediately open it up. 

  IMG_9839

Holy shit this thing is complicated, check out the screwdriver in the corner for scale.

First thing I hunted for were bad/swolen/leaking caps.  Didnt find any, which was a let down.  That night, I do a LOT of research, trying to dig up the service manual for it.  I never did find the correct one, but did find one for a similar panel.  There are some troubleshooting guides specifically for the LED code it was flashing.  I soon came to the conclusion while unhooking the 2 parts listed on the repair estimate that those parts are fine.  The estimate was bogus.

Hmmmm

Further testing, swapping, and measuring determines that the either the Power board (P1) or Scan Converter board (SC) is the culprit.  I measured a voltage called "Vbk".  This line supplies 195v to the Scan Converter board.  When powered on, I measured this @ zeroV!  However as soon as the unit is powered off, it jumps to normal voltage temporarily.  Also when this cable is disconnected from the SC board, and is measured off P1, it is normal voltage.  Bingo, the SC board must be drawing too much current, and shutting down that output!  There are also diagnostic LED's on several boards internally.  All light up bright, except the SC board.  It lights, but is quite dim.  Im pretty confident at this point the SC board is the problem.

IMG_9840

 

Jumped on ebay, $116 and a few days later:

IMG_9845

 

 

Jackpot!  The next day I bought a cheap universal remote, and played PS2 on it for about 4 hours straight.  Still works great!

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