Polaroid FLM-373B Power LED but no picture, already tried replacing caps

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  • pattheslat
    Member
    • Dec 2011
    • 25

    #41
    Re: Polaroid FLM-373B Power LED but no picture, already tried replacing caps

    It looks like that is the correct data sheet for this power supply, that is an impressive find. I still can't determine where PS_ON is though, I don't see it labeled anywhere on the board. I've attached a couple pictures of where the main board plugs in, hopefully that will be helpful. Sorry for the quality of the pictures, I lost my camera charger when I moved so I had to use my phone.
    Attached Files

    Comment

    • tom66
      EVs Rule
      • Apr 2011
      • 32560
      • UK

      #42
      Re: Polaroid FLM-373B Power LED but no picture, already tried replacing caps

      PS_ON is sometimes marked ON/OFF or STB (as it looks like in this case.)

      Use your multimeter to check if PSON is staying on when trying to turn the TV on.
      Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
      For service manual, schematic, boardview (board view), datasheet, cad - use our search.

      Comment

      • selldoor
        Slow Learner
        • Dec 2010
        • 7870

        #43
        Re: Polaroid FLM-373B Power LED but no picture, already tried replacing caps

        Thought it might be Pin3 Connector 105- see attachment
        but that differs from your picture ? Hmmm! Perhaps not the correct data sheet?
        Attached Files
        Last edited by selldoor; 01-26-2012, 06:40 AM.
        Please upload pictures using attachment function when ask for help on the repair
        http://www.badcaps.net/forum/showthread.php?t=39740

        Comment

        • pattheslat
          Member
          • Dec 2011
          • 25

          #44
          Re: Polaroid FLM-373B Power LED but no picture, already tried replacing caps

          Ok, this is interesting... STB (PS ON) is staying at a constant 5 volts even after my power board output voltages drop to zero. I'm thinking this maybe points to the power board being at fault?

          Comment

          • tom66
            EVs Rule
            • Apr 2011
            • 32560
            • UK

            #45
            Re: Polaroid FLM-373B Power LED but no picture, already tried replacing caps

            Originally posted by pattheslat
            Ok, this is interesting... STB (PS ON) is staying at a constant 5 volts even after my power board output voltages drop to zero. I'm thinking this maybe points to the power board being at fault?
            Hmm. Yes, that does seem likely. I should have asked you to check this; it slipped my mind but I recently came across an LG Plasma where I thought the problem was the power supply but it was the main board turning it off. In this case, it looks like it is genuinely the power board at fault.

            Can you unplug the main board from the PSU and connect the 3.3k resistor from 5V standby to STB, and see if the supply fires up?
            Last edited by tom66; 01-27-2012, 01:53 AM.
            Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
            For service manual, schematic, boardview (board view), datasheet, cad - use our search.

            Comment

            • PlainBill
              Badcaps Legend
              • Feb 2009
              • 7034
              • USA

              #46
              Re: Polaroid FLM-373B Power LED but no picture, already tried replacing caps

              If that doesn't work, check the voltage at the STB pin WITHOUT the resistor to 5V standby. If it is still at 5 volts, try pulling it to ground. I have encountered power supplies that are turned on by pulling the SBY input low.

              PlainBill
              For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

              Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

              Comment

              • tom66
                EVs Rule
                • Apr 2011
                • 32560
                • UK

                #47
                Re: Polaroid FLM-373B Power LED but no picture, already tried replacing caps

                Originally posted by PlainBill
                If that doesn't work, check the voltage at the STB pin WITHOUT the resistor to 5V standby. If it is still at 5 volts, try pulling it to ground. I have encountered power supplies that are turned on by pulling the SBY input low.

                PlainBill
                The datasheet says active high but it certainly could be active low. Wouldn't be the first time a dodgy datasheet has been encountered.
                Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                Comment

                • PlainBill
                  Badcaps Legend
                  • Feb 2009
                  • 7034
                  • USA

                  #48
                  Re: Polaroid FLM-373B Power LED but no picture, already tried replacing caps

                  Originally posted by tom66
                  The datasheet says active high but it certainly could be active low. Wouldn't be the first time a dodgy datasheet has been encountered.
                  That's the point. LOGICALLY a standby input would turn off the main supply (standby) when the input was high, and a PS_ON input will turn on the main supply when it is high. But there is no consistency.

                  PlainBill
                  For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                  Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                  Comment

                  • pattheslat
                    Member
                    • Dec 2011
                    • 25

                    #49
                    Re: Polaroid FLM-373B Power LED but no picture, already tried replacing caps

                    Ok, tried a few things. With everything unplugged and a resistor between 5VSB and STB, the power supply outputs all the correct voltages. With the inverter board plugged in and the resistor connected, the voltages are also all correct. When the main board is connected, however, the voltages all drop to zero.

                    With everything plugged in, connecting the resistor between GND and STB has no effect. I'm kind of afraid of running a direct jumper wire between GND and STB because I don't want to blow everything up, but if you guys think I should try that to see what happens I will.

                    Comment

                    • PlainBill
                      Badcaps Legend
                      • Feb 2009
                      • 7034
                      • USA

                      #50
                      Re: Polaroid FLM-373B Power LED but no picture, already tried replacing caps

                      No need to jumper the STB input to Gnd. Since the resistor to 5V standby turns the power supply on, the main board is overloading the power supply, causing it to shut down. Now you have the enviable task of finding out which component on the main board is at fault.

                      PlainBill
                      For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                      Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                      Comment

                      • pattheslat
                        Member
                        • Dec 2011
                        • 25

                        #51
                        Re: Polaroid FLM-373B Power LED but no picture, already tried replacing caps

                        Originally posted by PlainBill
                        Now you have the enviable task of finding out which component on the main board is at fault.

                        PlainBill
                        Well this should be a great time. There's a replacement main board on ebay for $80 that I might just grab, I feel like I'm not gonna be able to figure this one out. I've determined that when I unplug the wire I circled, the TV mostly powers up (backlight comes on, but nothing appears on screen), so something powered by that is causing the problem. I'm thinking this is still gonna be quite difficult though.
                        Attached Files

                        Comment

                        • tom66
                          EVs Rule
                          • Apr 2011
                          • 32560
                          • UK

                          #52
                          Re: Polaroid FLM-373B Power LED but no picture, already tried replacing caps

                          http://www.youtube.com/watch?v=XhqwC...el_video_title
                          Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                          For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                          Comment

                          • pattheslat
                            Member
                            • Dec 2011
                            • 25

                            #53
                            Re: Polaroid FLM-373B Power LED but no picture, already tried replacing caps

                            Ha, that is brilliant. I'll give that a shot, thanks for the link.

                            Comment

                            • pattheslat
                              Member
                              • Dec 2011
                              • 25

                              #54
                              Re: Polaroid FLM-373B Power LED but no picture, already tried replacing caps

                              Thought maybe you guys who have helped me would like an update on this... The "freezer spray" test didn't help figure anything out, but by hooking up a 9 volt battery to the pin that was causing problems, I was able to narrow the problem down to a tiny little area by checking voltages across the series of capacitors on the board (one had voltage across it, then the traces went through a few tiny little surface mount things, and the one after that read 0v).

                              I realized that even if I could figure out specifically which component was causing the problem, I don't have the skill to solder a component that tiny, and decided to just order a new main board from ShopJimmy for $65 when I get my next paycheck.

                              Comment

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