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P502UI-B1E shutdown automatically after 75s followed by power light blinking 15x

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    P502UI-B1E shutdown automatically after 75s followed by power light blinking 15x

    History

    - Got TV free. Prior owner claims Vizio logo shows up then nothing. He found U202 EEPROM replacement info (I know NickTV says its never EEPROM haha). Lifted 5 pads removing U202 without proper tools and thought thats end of main board. Gave the TV to me.

    - I repaired U202 pads and connections. Soldered on prior owner purchased aftermarket EEPROM (original EEPROM was tossed). TV boots to VIZIO logo, then goes blank, shutsdown after a min or so and power on light blinks a number of times.

    - Fixed 2 circa 2015 Vizios before with classical main board BGA failures so am familiar with these. Hot air gun the heatsink for about a min. same behavior.

    - Finally figured out this TV does not show "no input source" and stays blank for about 20s before menu can be summoned. So hit menu, reset the TV, setup default sources (I have antenna). Everything seems to work (antenna channel programming worked, USB movie playback worked, HDMI from fireTV worked) But reliably shutdown 75s after power on and blinks 15 times. Also did a factory reset and no sleep timer on.

    - Antenna channel scan takes awhile and completes without hitting the 75s shutdown. Did it 3x, all completed without shutdown. It has to be in the process of scanning to avoid shutdown. Even if at menu just before "Begin Scan", TV will shutdown in 75s after power on.

    - After 75s auto shutdown, in 75-80s, LED will blink 15x and just repeat a few times between 80s pause and 15x blinking.

    A couple of questions

    1. Does 75s + 15x blinking provide any hint? I'd guess not as my prior encounter with dying circa 2015 Vizio main board with BGA solder issues typically had similar behavior.
    2. Think I can rule out the aftermarket EEPROM since TV is completely functional for 75s?
    3. Next step is probably oven bake main board at 380F for 10min? I'd get another main board but they are rare and $$$.
    Last edited by howardc64; 11-28-2020, 05:54 PM.

    #2
    Re: P502UI-B1E shutdown automatically after 75s followed by power light blinking 15x

    I think the problem is still software, tell me about tv, is it a smart tv? I s it maybe Android? The best way to diagnose i think is to connect its serial debug port to pc via terminal prog and see the log and inspect it for damaged partitions. bye.

    Comment


      #3
      Re: P502UI-B1E shutdown automatically after 75s followed by power light blinking 15x

      Update

      A few hours later, TV behavior getting weirder. Now no more Vizio logo at power on. But did display default antenna source quickly. Then it didn't even do that. Just blank (back light goes on) and then shut off.

      Looks like a candidate for oven bake reflow.

      Comment


        #4
        Re: P502UI-B1E shutdown automatically after 75s followed by power light blinking 15x

        yes.

        Comment


          #5
          Re: P502UI-B1E shutdown automatically after 75s followed by power light blinking 15x

          Update:

          Toaster oven reflow worked (380F 10min). We'll see how long it last. A couple of notes

          - Big heat sink was removed for reflow so I can apply proper thermal paste afterwards. Will mount it back with some self tapping screws so I can avoid dealing with desoldering removal if need to again.

          - Didn't pull the small heat sink on the underside because didn't know how it was mounted). It fell off during reflow (luckily didn't pull off any SMT components). Mount is just a thermal pad and a L shaped black sticky rubber. Black rubber shrunk with heat. I'll just replace it with some thermal pad. For those doing this in the future, you'll want to remove this heat sink to minimize chance of pulling off component when it falls off during reflow. I've seen other version of this board on 2 other Vizio TVs, other boards don't have this heat sink so might not be all that important.

          Tested the TV without heatsink and the lower BGA chip surface burnt my finger tips inside 20s. These things get really hot fast. I'm contemplating skipping the big heat sink and mount a 50x50mm GPU heatsink + fan on it directly. Holes for the big heat sink offers a diagonal mounting point for this lower BGA. Top BGA is more challenging without good mounting holes nearby for a fan+heatsink combo.

          Comment


            #6
            Re: P502UI-B1E shutdown automatically after 75s followed by power light blinking 15x

            Happy to hear this at least partial success, keep us informed on how long it lasts!

            Comment


              #7
              Re: P502UI-B1E shutdown automatically after 75s followed by power light blinking 15x

              How do you protect the white connectors from melting?

              Comment


                #8
                Re: P502UI-B1E shutdown automatically after 75s followed by power light blinking 15x

                Originally posted by Davi.p View Post
                Happy to hear this at least partial success, keep us informed on how long it lasts!
                Unfortunately doesn't last. Proper BGA flow equipment required. Proper BGA removal + reball with leaded balls probably is long lasting solution.

                https://youtu.be/IkFCE42zoLM?t=330

                So far, the ONLY success I've had with toaster oven reflow is a Nintendo Switch logic board. Still running after 2 years. All TV main board reflow efforts failed soon after.

                Originally posted by kenpappas View Post
                How do you protect the white connectors from melting?
                380-400F doesn't melt the connectors.

                Comment


                  #9
                  Re: P502UI-B1E shutdown automatically after 75s followed by power light blinking 15x

                  380-400F doesn't melt solder properly, 424F is the melting point of solder, proper BGA equipment not necessarily required but it does help.

                  Comment


                    #10
                    Re: P502UI-B1E shutdown automatically after 75s followed by power light blinking 15x

                    Originally posted by diif View Post
                    380-400F doesn't melt solder properly, 424F is the melting point of solder, proper BGA equipment not necessarily required but it does help.
                    Yes understood, been reluctant to go to higher temps since toaster oven temperature control (and any regional hotspots) is impossible to control precisely.

                    Compared to BGA reflow equipment is programmed to spend very short period at melting temp and cools quickly afterwards. Also has multiple temperature probes on the BGA to monitor area temperature precisely.

                    My understanding from watching microscope image is once solder balls crack and form oxidization. Just melting of course doesn't clean up the oxidization and will eventually fail again. Hence, ball removal and cleanup is most desired.

                    I no longer have the TVs. Have acquired a BGA reflow preheater and have a good hot air station with temp probes... perhaps I'll try that next time.

                    Comment


                      #11
                      Re: P502UI-B1E shutdown automatically after 75s followed by power light blinking 15x

                      Flux is added to prevent oxidization. The balls are likely to crack again as they are lead free. When they are replaced they are replaced with lead balls.

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