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Phillips 55PFL5602/F7 T-Con failure?

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    Phillips 55PFL5602/F7 T-Con failure?

    Powers on
    Backlight comes on
    Plays sound (firestick menu sound through HDMI)
    LCD dark grey, no boot logo, no image

    I guessed Main board and PSU likely good and focused on T-Con + Panel. No experience debugging T-Con.

    T-Con


    Disconnecting one of the LCD flex to T-Con doesn't improve anything. Screen remains dark grey but the side with the pulled flex is slightly different shade of grey.

    T-Con Voltages

    All voltages are stable for about 20s then starts cycling at ~2s intervals. This is with both LCD flex connected, disconnected, or only 1 side disconnected. Seems cycling is not normal.

    F1 both side of fuse cycles between 12.03 <-> 12.1
    VCC 3.3 <-> 0
    VCORE 1.2 <-> 0
    HVDD 0.06 <-> 0
    VGH 1.38 <-> 0
    VGL1 -6.9 <-> 0
    V??2 (near D3) -14.8 <-> 0
    VCOM1 0.12 <-> 0
    VCOM2 0.33 <-> 0
    VA1/VA2 (not sure which is which from the label) 0.03 <-> 0 12.08 <-> 12.03
    VIN 12.08 <-> 12.02
    VST -14.8 <-> 0
    VCC1B 1.83 <-> 0
    VCOMRFB 0.13 <-> 0
    VDD 2.09 <-> 0
    V1/V4/V5/V6/V9 2.26 <-> 0
    V10/V13/V14/V15/V18 0.16 <-> 0

    T-Con does get pretty hot. Hotter than I would have expected but don't know what is norm.

    Main Board


    P-ON +12V shows 12.1v rock solid
    Cap near pin 51 of T-Con connector shows 12.08 <-> 12.10 with T-Con connected. Solid 12.10 without T-Con connected

    Testing Setup


    T-Con is assembled under the PSU and main board. Mostly covered by PSU. To read the test points, moved T-Con above with paper underneath for insulation and ground jumper to chassis. See last pic.

    Questions


    - What other test can be done? Don't have logic analyzer for clocks/waveforms
    - T-Con failure likely?
    - Should I expect white on 1/2 of screen with 1 panel flex disconnected from T-Con? I've seen this behavior before on a Samsung but perhaps its panel dependent?
    Attached Files
    Last edited by howardc64; 07-31-2022, 05:36 PM.

    #2
    Re: Phillips 55PFL5602/F7 T-Con failure?

    probably won't matter but for an experiment I would also ground the other side of the board and see if the voltages are still cycling.

    Comment


      #3
      Re: Phillips 55PFL5602/F7 T-Con failure?

      So, you basically have only 12v on t-con with cables hooked up? And you checked voltages when you removed cables and same no voltage?
      I assume no responsibility for any stupid suggestions I might post.

      Comment


        #4
        Re: Phillips 55PFL5602/F7 T-Con failure?

        Originally posted by nomoresonys View Post
        probably won't matter but for an experiment I would also ground the other side of the board and see if the voltages are still cycling.
        Yes thought about that. The 2 grounding pads are continuous but easy since all setup. See pic. The cycling remains.

        One thing I forgot to mention is inspecting the panel edge driver board in case of liquid drip (all clean). What I did find is the flex between the driver board and panel made a rubbing mark on the metal frame that encased it. Right where the filter caps/resistors is (but its on the other side so presumably the flex itself is the insulator). Not sure if that shorted out anything. I tape insulated it on reassembly for precaution. See pics
        Attached Files

        Comment


          #5
          Re: Phillips 55PFL5602/F7 T-Con failure?

          Originally posted by dskall View Post
          So, you basically have only 12v on t-con with cables hooked up? And you checked voltages when you removed cables and same no voltage?
          Did the following test combos to read voltages.

          - Everything is connected. Panel to T-Con, T-Con to main, main to PSU, PSU to backlight. IR and button panel to main. Skipped speakers.

          - Disconnect either one or both Panel to T-Con flex. Made no difference to the voltage readings.

          All T-Con voltage readings are the same in all these cases.

          I also tested main 12V near T-Con connector with T-Con connected and disconnected just to confirm the voltage cycling wasn't coming from main.

          Comment


            #6
            Re: Phillips 55PFL5602/F7 T-Con failure?

            ok, after looking at the testing above, it sure seems like the problem is the tcon, they're usually cheap enough on ebay, could try to narrow down to component level, might be a brain teaser tho.
            Last edited by nomoresonys; 07-31-2022, 06:40 PM.

            Comment


              #7
              Re: Phillips 55PFL5602/F7 T-Con failure?

              some there, just need to make sure you mach up the numbers on the white stickers, put that in for those looking on who might not know: https://www.ebay.com/sch/i.html?_fro...acat=0&_sop=15

              Comment


                #8
                Re: Phillips 55PFL5602/F7 T-Con failure?

                Thanks. I suppose a touch test to see what component heats up first might be worth a try. I'm assuming safe enough with no high voltage/currents. Don't have thermal cam (need to get one of those soon along with BGA reflow station haha) Also didn't find any shorted caps.

                And yes, t-con is cheap enough to try. On matching the white stickers... looks like only first few #/letters match. Rest looks like serial of some sort. There is a Desc and PN printed that has version #. Probably should match that. I believe the following are probably the key #s to match up

                DESC V16 55UHD TM120 v0.6. (seen other versions)
                PN 6070C-0586A (seen non As)
                White sticker should say 55 (seen other screen sizes) 6871L-4682A... (haven't been able to match beyond this sequence)

                BTW, LG is the T-Con board manufacturer. I know LG/Phillips used to JV on LCD South Korea new gen LCD factories. Maybe still does haha.

                Comment


                  #9
                  Re: Phillips 55PFL5602/F7 T-Con failure?

                  yes, guess its the first 5 big numbers on bottom of sticker: https://www.shopjimmy.com/philips-68...a-t-con-board/

                  Comment


                    #10
                    Re: Phillips 55PFL5602/F7 T-Con failure?

                    ok, its the first 5 numbers after the dash -4682A.
                    Last edited by nomoresonys; 07-31-2022, 08:06 PM.

                    Comment


                      #11
                      Re: Phillips 55PFL5602/F7 T-Con failure?

                      yes its a strange symptom, if the 12 volts for tcon coming from mainboard is steady, then going wonky at tcon, thinking it must be tcon or lvds cable at fault.

                      Comment


                        #12
                        Re: Phillips 55PFL5602/F7 T-Con failure?

                        Originally posted by nomoresonys View Post
                        yes its a strange symptom, if the 12 volts for tcon coming from mainboard is steady, then going wonky at tcon, thinking it must be tcon or lvds cable at fault.
                        Yes my thought as well. Good point on the LVDS cable. The contacts all look fine although the cable itself is folded a few times originally at factory (see pic) . Given the good contacts, T-CON seems most likely.

                        How does all the T-CON voltages look besides cycling? VDD VGH both looks off according to this post

                        https://www.badcaps.net/forum/showpo...0&postcount=19

                        I guess per suggestion in that post, can look for shorts between major power rails.

                        Originally posted by nomoresonys View Post
                        yes, guess its the first 5 big numbers on bottom of sticker: https://www.shopjimmy.com/philips-68...a-t-con-board/
                        Originally posted by nomoresonys View Post
                        ok, its the first 5 numbers after the dash -4682A.
                        And thanks for the shopjimmy reference, they highlighted the 5 key letter/numbers 4682A for my set.
                        Attached Files
                        Last edited by howardc64; 07-31-2022, 08:56 PM.

                        Comment


                          #13
                          Re: Phillips 55PFL5602/F7 T-Con failure?

                          You can use alcohol to find hot component.
                          I assume no responsibility for any stupid suggestions I might post.

                          Comment


                            #14
                            Re: Phillips 55PFL5602/F7 T-Con failure?

                            One more data. Keeps on pointing to T-Con. Here is a video of the TV with all boards and cables installed.

                            https://youtu.be/hB1Y03JH51k

                            Screen brightness cycles @ T-Con voltage cycling interval. Ignore the camera auto focus adjustment whenever brightness changes. Backlight is steady brightness (see through holes with back cover removed) so T-Con is basically changing the black levels of the LCD.

                            Comment


                              #15
                              Re: Phillips 55PFL5602/F7 T-Con failure?

                              HVDD looks to have no voltage what's the resistance to ground of L6 ?

                              Comment


                                #16
                                Re: Phillips 55PFL5602/F7 T-Con failure?

                                Hi, it seems could be a common problem with panel distribution boards, you call'em edge b., first of all check for shorts the bigger caps on those boards..
                                you are wishing bga station and ir cam and you want to remain with that horrible tester? Something doesn't turn back.. first purchase a better DMM my advice..

                                Comment


                                  #17
                                  Re: Phillips 55PFL5602/F7 T-Con failure?

                                  Originally posted by diif View Post
                                  HVDD looks to have no voltage what's the resistance to ground of L6 ?
                                  Thanks for the suggestion. Led me closer to finding the short

                                  L6 is 2.64k to ground. L2 8K L1 526 L3 0!

                                  Tracing L3 circuit led me to this post of the same T-Con with probably the exact same failure. My T-Con also gets hot (also without panel flex connected) but haven't tried to setup again to see if same QFN thats source of heat (but probably likely given the L3 short)

                                  https://www.badcaps.net/forum/showthread.php?t=74520

                                  Post #2 gave rough summary of the QFN chip and post #6 provides the schematic of similar circuit. On my board

                                  L3 = L0N4 on schematic. Short to ground on both sides
                                  Couldn't find the R9N2 and C4N6 equiv on my board
                                  D3 = D1N0 on schematic. VGL2 test point (hard to read, right next to D3) not short to ground. Couldn't find R2N4 equiv on my board.

                                  I guess could remove L3 to see if short is gone.

                                  Originally posted by Davi.p View Post
                                  Hi, it seems could be a common problem with panel distribution boards, you call'em edge b., first of all check for shorts the bigger caps on those boards..
                                  you are wishing bga station and ir cam and you want to remain with that horrible tester? Something doesn't turn back.. first purchase a better DMM my advice..
                                  T-Con voltage cycling occurs without panel distribution board flex connected so T-Con definitely looks bad (per found short above as well). But probably good to check the bigger caps on the distribution board just to make sure it wasn't the cause.

                                  And yes, need a better DMM haha.. Had a hand me down Fluke a few years ago but DIY energy was on fixing European cars back then...
                                  Last edited by howardc64; 08-01-2022, 10:51 AM.

                                  Comment


                                    #18
                                    Re: Phillips 55PFL5602/F7 T-Con failure?

                                    It's not much the fact of cycling without panel, but the fact that overheating also without panel that lets me suspect a bit the tcon now, is that heat enough to bother a bit the finger tip? The low resist. that you read on L3 against gnd is normal because L3 is connected to GND, it's an inverting topology.

                                    Comment


                                      #19
                                      Re: Phillips 55PFL5602/F7 T-Con failure?

                                      sure why not, remove L3 and see if the pads read shorted, I would test every cap and resistor around L3 first maybe.

                                      Comment


                                        #20
                                        Re: Phillips 55PFL5602/F7 T-Con failure?

                                        that is pretty bad that his tcon only lasted 4 months, wonder if there is any revisions for this tcon that maybe made it more reliable.

                                        Comment

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