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Samsung PN64E550D1F plasma – sound, no picture

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    Samsung PN64E550D1F plasma – sound, no picture

    The TV turns on and works normally for a short time but eventually the video shuts off and only the sound is playing. The problem has been getting worse over the past couple of weeks. Initially, unplugging for a while solved the problem and it worked properly for several hours until the next failure. Now it usually fails after a few minutes and unplugging does not always reset it to a good state. Also, it does appear that using the remote for functions like accessing the menu or changing the video input sometimes causes the failure to occur immediately, though changing the volume seems to have no effect. Also, the TV's IR receiver seems to be functioning poorly in general and doesn't always respond to the remote. Have tried it with different inputs and cables to rule out that issue.

    Opened it up and visually nothing seems out of the ordinary. I tested all of the fuses and they are fine. Caps appear to be normal. I tested the key voltages and when it is operating correctly they match the specs. After the picture goes out, the voltages (Vs, Va, Vsc, Ve) are abnormal, all under 10V. Only the standby voltage is holding steady at it's normal value of 5.3V.

    On the logic board there is an LED labelled LED2000 that flashes in a very slow cycle of about 6 seconds when the picture fails. Normally it flashes every second when working properly. I've read elsewhere that slow flashing indicates a fault on the logic board. I'm thinking that the logic board might be incorrectly putting the TV into a low power or sleep mode state.

    The X and Y-mains seem to be functioning correctly because the picture is flawless when the TV is in a good state. Replacing the logic board would be the most obvious solution. Or is this maybe a case of the power board being on the verge of total failure?

    Has anyone seen a similar problem before or have any advice about other things to check before I go and order the logic board?

    #2
    Re: Samsung PN64E550D1F plasma – sound, no picture

    with those gradual symptoms I usually suspect bad capacitor/s, try heating a little section of caps on the powerboard at a time with a hairdryer and see if tv comes on, if only for a little while, can try it on the other boards too.
    Last edited by nomoresonys; 03-24-2022, 05:43 PM.

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      #3
      Re: Samsung PN64E550D1F plasma – sound, no picture

      Thanks, I tried a hairdryer for a few minutes but the screen didn't come back on.

      I had it unplugged all day and it was working initially. I let it run normally for 10 minutes until I pressed the menu button which immediately caused the screen to shut off. The firmware is up to date but it seems like it could be a software/logic issue if remote control functions lead to a failure. But maybe that's just wishful thinking since the logic board is the cheapest/easiest fix.

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        #4
        Re: Samsung PN64E550D1F plasma – sound, no picture

        ok, the hairdryer thing doesn't rule out bad cap/s, it will lower the esr in a marginal cap for a short period but if a cap is too far gone the heating won't work, your right it might be that logic board, did you try a factory reset?

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          #5
          Re: Samsung PN64E550D1F plasma – sound, no picture

          could try unplug from power about 15 minutes, before plug back in, press and hold power button on tv for 60 seconds release and plug tv back in and try, won't hurt but probably won't solve it tho.

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            #6
            Re: Samsung PN64E550D1F plasma – sound, no picture

            Thanks, I have tried the factory reset and it doesn’t help.

            I’m pretty sure there’s a problem with the power board, maybe a short or bad transistor. I noticed PS_ON pin is showing 133.8V which surely can’t be right. The troubleshooting manual I found says it should be 3.3V when in standby and the main board pulls it down to 0V when the TV is turned on to wake up the power board. Oddly, during the brief times that the TV works properly it’s still showing 133.8V but it’s was probably held at 0V just long enough to startup correctly. I guess I’ll have to pull out the board and test each component.

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              #7
              Re: Samsung PN64E550D1F plasma – sound, no picture

              are you sure its reading volts and not mv = millivotes?

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                #8
                Re: Samsung PN64E550D1F plasma – sound, no picture

                This power supply has a lot of trouble with cold solder joints. Start with checking the solder joints on the transistors for the vs and va circuits and anything suspect redo those solder joints.

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                  #9
                  Re: Samsung PN64E550D1F plasma – sound, no picture

                  Yeah I’m blind, it was in mV. On my meter the ‘m’ pops up in an unusual location not at all close to the ‘V’.

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                    #10
                    Re: Samsung PN64E550D1F plasma – sound, no picture

                    That's a good idea to touch up the joints. I also uploaded some photos of the board. Not totally sure how to identify bad joints but I think I see some really suspect ones, especially around QS802 in the 3rd photo.
                    Attached Files

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                      #11
                      Re: Samsung PN64E550D1F plasma – sound, no picture

                      Yes qs802 and qs804 are good to start with. Also check out ds802 and ds804 and qp701 qp802.

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