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Panasonic TC-P65S1 mainboard

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    Panasonic TC-P65S1 mainboard

    Background:

    This TV has a weird fault where there is signal corruption on all the HDMI inputs, when running at 1080p 60Hz (which is a supported mode). I've tried many different cables and even different sources, with no difference. Running at lower resolution or refresh rate there is no problem at all.

    The corruption presents itself as the signal occasionally going black, sometimes going all blocky, but sometimes is very subtle and presents itself as stray pixels flashing randomly on the image.

    As the mainboard warms up, the corruption becomes less and less. If I hit the mainboard with a heat gun and get it to a nice toasty 70C, the problem eventually completely disappears (only to start progressively coming back as the board cools off). The cooler the board, the worst the problem becomes. In particular, the greatest effect seems to come when heating/cooling the main processor (IC8001).

    Initial Troubleshooting:

    All power supply voltages and on-board regulators checked to proper voltage and for the presence of any ripple. Nothing abnormal found.

    All electrolytics on mainboard tested for capacitance and ESR, all checked out ok.

    Replaced IC4503 (HDMI switch), absolutely no difference.

    Basically I'm out of ideas what else to try, other than replacing IC8001 (Toshiba TC90413XBG) but this being a 456 pin BGA I don't like my chances.

    The Hunt for a Replacement Board:

    This TV uses board part number TNPH0786, suffix AM. I can't find this board anywhere at all. There are a lots of other TVs that used the same board but with a different suffix, they appear from pictures to be the same board hardware-wise.

    Am I correct in my assumption that the difference between the different board suffixes would be the firmware configuration, since the hardware appears to be the same?

    What are the potential pitfalls of dropping in a board from a TV of smaller size but same resolution? Could this potentially work?

    As a last resort, could I swap the EEPROM chips over to the replacement board so it has the correct firmware?

    Anyone even run into something like this before?

    #2
    Re: Panasonic TC-P65S1 mainboard

    If you aren't looking to get the current board fixed, you can use one with a different suffix if you swap the eeproms. If you get a board for a different TV and just plug it right in, you may break your panel. I know that one from experience. The eeprom I believe is IC9001 near the BGA that feeds into the ribbons leading to the panel.
    Swapping it should take care of it.
    I was also told but never have done this myself that you could change some of the resistors around where the chart is that determins which suffix it is and that would also work. Never tried that one so I don't know if it's true or not.

    Comment


      #3
      Re: Panasonic TC-P65S1 mainboard

      Originally posted by Nick's Tvs View Post
      If you get a board for a different TV and just plug it right in, you may break your panel. I know that one from experience.
      I kind of suspected that. Different panels likely need different timings to drive them properly.

      Originally posted by Nick's Tvs View Post
      The eeprom I believe is IC9001 near the BGA that feeds into the ribbons leading to the panel.
      Swapping it should take care of it.
      So no need to swap the two larger EEPROMs (IC9303 and IC8502)?

      Originally posted by Nick's Tvs View Post
      I was also told but never have done this myself that you could change some of the resistors around where the chart is that determins which suffix it is and that would also work. Never tried that one so I don't know if it's true or not.
      Looks to me like the traces from those resistors/jumpers don't go anywhere other than some test points on the bottom of the board. Though it is possible it's connected to some traces on inner layers of the board through the vias. I'll have to measure these and see if there's any voltages appearing on the open jumper positions when powering on the TV.

      Comment


        #4
        Re: Panasonic TC-P65S1 mainboard

        I think it may be wiser to simply reflow your original board so it would be risk free and worst case you break the board that you were going to replace anyways.

        As for the IC9001 I mentioned I am not 100% sure. Now i have never performed this swap with this TV specifically, I have only dones it with several of the newer panasonic type models. Now the reason it's not going to be a Nand chip or EMMC or other large chip is because those control the software of the main board. What we want to make a change on is the logic board. Now panasonic doesn't have a logic board in their sets instead they integrate it with the main board, so what that means is that we have to focuse on the area near all the outgoing LVDS ribbons as that will be the area where the logic board portion is located. Now since that's the only chip I see there I assume it is the one, but once again, I can't confirm this to be 100% sure. If you want to be safe and would preffer to just swap out all the chips, that would work to.

        Comment


          #5
          Re: Panasonic TC-P65S1 mainboard

          Well I've confirmed both through the schematics and scope measurements that the suffix jumpers are pretty much just a decoration. They don't connect to anything other than some test pads on the bottom of the board. I assume this allows automated testing equipment in the factory to quickly identify what version of board it's dealing with.

          Originally posted by Nick's Tvs View Post
          I think it may be wiser to simply reflow your original board so it would be risk free and worst case you break the board that you were going to replace anyways.
          The dilemma is with the current board I have a TV that functions perfectly fine with 24Hz content (basically most any TV STB, DVD, Blu-Ray sources), so could still be a useful TV to someone that doesn't do any gaming or connect a computer to the TV.

          If I kill the board, the TV is a brick after that point.

          I also don't have a reflow oven to be able to reflow the entire board. I could reflow IC8001 alone, which is the most likely culprit, but this is a larger BGA than I've ever attempted before. Keep in mind that all I've got is a hot air rework station (Quick 861DW), nothing fancier than that.

          The larger flash EEPROM IC9303 connects directly to the FPGA responsible for driving the plasma display (the large IC next to the ribbons), so I suspect it may contain important code related to performing this function whether or not that code is model-specific, no way to know without getting another board and dumping the contents of both.

          I agree though that IC8502, the flash EEPROM associated with the main CPU, holds the software and can probably be left alone.

          Comment


            #6
            Re: Panasonic TC-P65S1 mainboard

            Well, the replacement board, TNPH0786 AJ suffix came in, after sitting for 4 weeks in customs

            I swapped over the two EEPROMs that reside near the FPGA by the ribbon cables (they indeed had different data between the two boards). I put the board in the TV and... no good. Picture was overly bright and washed out. Thinking that maybe something in the software for the CPU had something to do with it, I swapped that over too. No difference. For good measure I also applied jumpers for the AM suffix, as expected, this did not make any difference either. These are the only 3 EEPROMs anywhere on the board, everything else hardware wise appears identical between the two boards as far as I could see, with the exception of the AJ board having a VGA connector which is not populated on the AM board.

            The board I purchased was a used board pulled from another TV, so it is quite possible it was defective to begin with.

            At this point, running out of patience and having very little to lose, I attempted reflowing the main CPU. This, evidently, ended up killing it for good, as even after I removed it, cleaned off the old solder, reballed it, and resoldered it, was still dead. No sure why, maybe I used too much heat for too long during the initial reflow, or perhaps it was already on its way out and the heat was the final nail in coffin.

            Out of desperation, I removed the CPU from what I will now call the "donor board" and soldered it onto my original board. I really was not expecting it to work, especially considering my BGA re-balling job is far from what you would consider "textbook" (I don't have solder paste or stencils). Put the board in the TV, not expecting anything to happen and... turns on and the menu appeared! Plugged in a PC to an HDMI port and got a perfect image, and no more of the weird glitches and corruption that was happening before.

            Not sure if this repair will hold up in the long run, only time will tell I suppose, but this is the best I could manage for now given the exact replacement board for this TV is literally unobtainium.

            I'll also have to add solder paste and BGA stencils to my electronics repair arsenal if I do any reball jobs in the future, to do things properly. I'm still amazed that this worked, I literally just put a crap ton of flux on both the board and the bottom of the BGA IC and ran my soldering iron with some leaded solder over the pads to get as much solder to stick to them as I could.

            Comment


              #7
              Re: Panasonic TC-P65S1 mainboard

              Just when I thought I had this thing fixed up...

              Found out the TV's HDMI inputs, for whatever reason, will only accept input from a PC (laptop). When my HT receiver or Blu-Ray player are connected, I get no video.

              What could cause this? Obviously the HDMI ports all work (electrically at least) since I get video from the laptop just fine.

              Did I maybe create some sort of HDCP handshaking issue by swapping the CPU from another board? I'm not sure if there's anything built in the CPU that is unique to each one or not. Can't find full datasheet for the Toshiba TC90413XBG

              Comment

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