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Samsung PN51D550C1FXZA no power up

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    Samsung PN51D550C1FXZA no power up

    Okay working on this for a Corpsman and his wife. Here were the symptoms:
    Plug it in, wait for a bit and would hear about five clicks from the PS. Front LED would start to blink....2 times, short pause, 2 times, short pause, 2 times, short pause, 2 times, short pause, 2 times, long pause repeat....

    Was unable to locate a LED error code diagram so we opened it up.

    With everything plugged in Vs was 0V. Did have 5V at STNDBY and 3.25V at PWRON.

    Decided to go for a resistance reading, vice voltage reading for the Vs. With everything connected, Vs was shorted to ground.
    Unplugged the X main and Vs read an open with black on ground and 474 ohms with red on ground.
    Unplugged the Y main and Vs read an open with black on ground and 847 ohms with red on ground.

    Did some checks on each of the cards: Vs on the connector pins to ground,
    X main showed a short, Y main shows a open, PS shows a open.

    On the X main: SVC_VS is shorted to SVC_GND. Believe all but three of the power transistors are shorted (quick check).

    I'm about 90% sure the X main is the problem, several transistors read low resistance from one leg to another.

    The problem I have is finding or being sure of what board would work in this TV.
    The board number, as I understand it, is LJ92-01763A, with a revision of AA4. The barcode has the 763A and AA4 on it. It also has large stamped letters on the top of the heatsink of "DFG", not sure if this has any meaning or not. The other thing I have noticed, different from other boards I have looked at, this board has four large red capacitors in a row (other boards have three).

    Of course the three capacitor boards are readily available and cheaper, the four capacitor boards are expensive and hard to find. Yet, they are all advertised as the same board.

    Any assistance would be appreciated.
    Attached Files

    #2
    Re: Samsung PN51D550C1FXZA no power up

    Unfortunately you can't use the 3-capacitor one as it is the 720p board (your set is 1080p), however it *may* be possible to upgrade a 720p one with the good parts from your 1080p board. It also may be possible to repair it.
    Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
    For service manual, schematic, boardview (board view), datasheet, cad - use our search.

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      #3
      Re: Samsung PN51D550C1FXZA no power up

      Thanks Tom, for ruining my day!!
      Just saw your link to service manuals....great set up! I was hoping to add to you list but you already have the fast track and troubleshooting guide I had found.

      Do you know if the "DFG" designation, on top of the heat sink, means anything?
      Is there a better part number to use when looking for this board?

      I am down to either spending the extra on the board, or repairing this one. Not sure where to start on the repairing of this board.....would like a schematic of the board.

      From the checks I have made: D4103,Q4101, Q4104, D4302 are all shorted. Q4301 and Q4302 are shorted on one side (assuming pins are source, gate, drain) these would be shorted gate to drain.

      Now the question would be: what would cause all of these to go bad or is it some sort of chain reaction? If these are bad, is there a standard replacement procedure of parts to replace?

      I can't even seem to cross the part numbers to find the correct parts! D4103 and D4302 are AUK 61825 SF10A400H; Q4101 and Q4104 are 30G124; and Q4301, Q4302 I can't make out they are hidden behind some capacitors.

      Thoughts?
      Attached Files

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