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Samsung PS51D450A2M plasma - no pic or sound

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    Samsung PS51D450A2M plasma - no pic or sound

    My first post....my first plasma.....a Samsung P51D450 which won't start....heartbeat LED blinks about every 6 sec. No sound or video. Relay clicks on and off and my analogue multimeter connected to Vs doesn't stir.

    Power is fed to Xsus from the Ysus board. I can start the smps by disconnecting Ysus (and therefore Xsus) *and* the Ysus ribbon cable from the control board. Then Vs and Va sustain their correct voltages and the heartbeat LED blinks ever y sec. So the smps appears good, but still no sound or chime. If I isolate Xsus (both with or without the Xsus ribbon) the Ysus fault remains.

    The Ysus PBA is a LJ92-01760A, see pic below. Can I be reasonably sure the fault is on this board somewhere? I've checked out all the videos and forums I can find. I have multimeters and 'scope but no ESR meter. I've resoldered anything that looks suspicious, and used an ohmmeter to check for o/c's and s/c's - nothing obvious. I haven't found any fuses to test - should there be?

    Does it make sense to swap out the Ysus board - $60-odd - before I get sound/chime? Is there any way to check the signal/video board without the panel and therefore no on-screen menus?

    I note CapKid's advice to forget trying to fix Ysus or Xsus at the component level, and other comments that an Xsus fault can take out the Ysus board or viceversa. Is this common, and what are my chances of needing both boards? Is it unwise to buy and swap out Ysus without Xsus?

    Any ideas anyone?
    Attached Files

    #2
    Re: Samsung PS51D450A2M plasma - no pic or sound

    With the set off check the various test points highlighted on the Ysus board, SVC_VS, VSCAN, VS, VE etc to chassis for short circuits.
    Willing to help but I'm no expert.

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      #3
      Re: Samsung PS51D450A2M plasma - no pic or sound

      Thanks Dick - After 50+ years in electronics, why didn't I think of that? Doh! But having no idea what the X&Ysus boards do does add to the confusion. Is a circuit schematic available anywhere?.....anything similar would sure help. Result: Ysus seems ok, Xsus has VS s/c to chassis. Is there a cunning technique to find the short or do I just start cutting traces to isolate the bad spot?

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        #4
        Re: Samsung PS51D450A2M plasma - no pic or sound

        Check all the IGBTs and Diodes attached to the heatsink for short. If shorted, replace them with the same part number.

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          #5
          Re: Samsung PS51D450A2M plasma - no pic or sound

          Thanks Sevenqi - Sorry for the tardy response - I didn't expect to be outa town this week. Once off the chassis, the Xsus board became very bent/distorted, like a dish. Not much discolouring, but heat I guess. So just test bit by bit, huh? Ok, I'll get into it when I'm back in the 'shop next week, and post back how I get on. - thanks again.

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            #6
            Re: Samsung PS51D450A2M plasma - no pic or sound

            I don't know if this manual is similar to your set but it should be a useful guide for you.
            Last edited by dick_barton; 07-06-2016, 03:46 PM.
            Willing to help but I'm no expert.

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