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Hitachi LE42H508 no power....

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    #1

    Hitachi LE42H508 no power....

    Powered down while watching, unplugged from wall, checked outlet, replugged, came back on for about 3 minutes then died and never came back on.
    If I unplug it, wait and replug and power on, I sometimes get a momentary blue horizontal "strobe" and that's it.
    Did some online reading, took off the back cover and using a multimeter, checked the fuse for continuity (good) but could not get any DC volts outbound from the power supply board so I ordered one. Got it today and.... no change.
    So what else could it be? I tested the pins in the closeup using the legend and never got any volts off of PS-ON or BL-ON individually. I was only able to get 12.3V on all 3 at the bottom when I jumped the top 2 (PS-ON and BL-ON).
    oh, and this is the power supply board: 810426667






    Any help appreciated.
    Tags: None
    #2
    Re: Hitachi LE42H508 no power....

    What are your voltages in standby?
    I assume no responsibility for any stupid suggestions I might post.

    Comment

      #3
      Re: Hitachi LE42H508 no power....

      That's the oddest thing... I could not get any readings on either of the top 2 pins even when jumped together. Yet the bottom 3 would read 12.3V ....
      I didn't even try jumping the top 2 pins on the replacement power supply,I unboxed it,swapped it in, plugged the TV in,and tested with pins connected to the ribbon and nothing.

      Comment

        #4
        Re: Hitachi LE42H508 no power....

        Might try disconnecting t-con. When you power it on do you ever get any pson voltage
        I assume no responsibility for any stupid suggestions I might post.

        Comment

          #5
          Re: Hitachi LE42H508 no power....

          Originally posted by dskall View Post
          Might try disconnecting t-con. When you power it on do you ever get any pson voltage
          You lost me... That'll require a much more detailed walk thru please. this is my 1st attempt at a TV teardown... I usually use a M/M on motorcycles or cars.

          TIA

          Comment

            #6
            Re: Hitachi LE42H508 no power....

            When you jump the 12V DIRECTLY to the PS-ON pin and the BL-ON PIN, Did you remove the connector going back to the main board first? If you did not then you could now have damaged the switched Transistors on the main board.
            Never stop learning
            Basic LCD TV and Monitor troubleshooting guides.
            http://www.badcaps.net/forum/showthr...956#post305956

            Voltage Regulator (LDO) testing:
            http://www.badcaps.net/forum/showthr...999#post300999

            Inverter testing using old CFL:
            http://www.badcaps.net/forum/showthr...er+testing+cfl

            Tear down pictures : Hit the ">" Show Albums and stories" on the left side
            http://s807.photobucket.com/user/budm/library/

            TV Factory reset codes listing:
            http://www.badcaps.net/forum/showthread.php?t=24809

            Comment

              #7
              Re: Hitachi LE42H508 no power....

              Originally posted by budm View Post
              When you jump the 12V DIRECTLY to the PS-ON pin and the BL-ON PIN, Did you remove the connector going back to the main board first? If you did not then you could now have damaged the switched Transistors on the main board.
              By directly do you mean bridge the PS-ON and BL-ON with a tiny alligator? because that's all I did WITH the connector disconnected. The only testing with the connector in place was with the MM in DC, the blk probe on one of the GND pins and using the red probe on PS-ON, BL-ON and the 12.3 (x3) with no readings whatsoever. I tried using the frame as ground with no difference.

              Comment

                #8
                Re: Hitachi LE42H508 no power....

                So you only connected the ps-on and the bl-on together? Which will give you nothing because neither have voltage on them.
                I assume no responsibility for any stupid suggestions I might post.

                Comment

                  #9
                  Re: Hitachi LE42H508 no power....

                  I had watched a video online recommending to test this way...
                  Regardless of my poor testing, any suggestions?
                  Since I bought and replaced the PSU and still no change, what's the next step?

                  Thanks

                  Comment

                    #10
                    Re: Hitachi LE42H508 no power....

                    If you are not getting a ps-on voltage when you try to power on then I would say it is mainboard problem.
                    I assume no responsibility for any stupid suggestions I might post.

                    Comment

                      #11
                      Re: Hitachi LE42H508 no power....

                      The LEDs are bad. That will take the PS down. If you unplug the main. The 12v will stay. Is not the Main, is the LEDs. Trust me.

                      Comment

                        #12
                        Re: Hitachi LE42H508 no power....

                        Simple test, if tv has pullup resistors, backlight if working will come on and stay on, do it just like this, make sure tv is unplugged, disconnect powersupply board from mainboard, plug tv in turn it on see if backlights come on.
                        Last edited by nomoresonys; 03-16-2018, 10:31 AM.

                        Comment

                          #13
                          Re: Hitachi LE42H508 no power....

                          http://www.shopjimmy.com/hitachi-810...upply-unit.htm is this the powersupply?

                          Comment

                            #14
                            Re: Hitachi LE42H508 no power....

                            Is possible you got a dud with the new/used powersupply board, testing always beats jumping to conclusions.

                            Comment

                              #15
                              Re: Hitachi LE42H508 no power....

                              https://elektrotanya.com/?q=keres Put your model number in and see if they have a service manual, always makes things easier with one.

                              Comment

                                #16
                                Re: Hitachi LE42H508 no power....

                                Originally posted by Bullykatz View Post
                                By directly do you mean bridge the PS-ON and BL-ON with a tiny alligator? because that's all I did WITH the connector disconnected. The only testing with the connector in place was with the MM in DC, the blk probe on one of the GND pins and using the red probe on PS-ON, BL-ON and the 12.3 (x3) with no readings whatsoever. I tried using the frame as ground with no difference.

                                You were close, you need voltage, so jumper the ps_on with 12 v, with mainboard DISCONNECTED, then see if your voltages have returned.
                                Last edited by nomoresonys; 03-16-2018, 11:14 AM.

                                Comment

                                  #17
                                  Re: Hitachi LE42H508 no power....

                                  You may need to jumper bl on ps on and 12 v. all together, not exactly sure on that.

                                  Comment

                                    #18
                                    Re: Hitachi LE42H508 no power....

                                    If you can't get your ps on voltage with all other boards disconnected and the powersupply jumpered correctly, then the problem lies with the powersupply. If you can't get the standby voltage, look towards the powersupply.
                                    Last edited by nomoresonys; 03-16-2018, 12:12 PM.

                                    Comment

                                      #19
                                      Re: Hitachi LE42H508 no power....

                                      https://www.youtube.com/watch?v=qxG3hmmvkJs

                                      Comment

                                        #20
                                        Re: Hitachi LE42H508 no power....

                                        n/a

                                        Comment

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