Polaroid PSU output power

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  • kenny1070
    Senior Member
    • Oct 2013
    • 65
    • USA

    #1

    Polaroid PSU output power

    This unit is a Polaroid FLM 3701 (monitor only / no tuner)
    Build date 2005

    It utilizes a KAS200-5s241812xL Power Supply (LC-37K7)

    This thread is a carry-over from a blown PFC Film Cap (474k 450v), which has since been solved.

    BACKGROUND:

    Came home one day after a really bad lightning storm = TV won't turn on.
    No power - no red/blue lights - dead.

    Pulled out the Power supply board and replaced all the Caps with new ones from LCD Alt.
    All but the 450v 150uf large cap - extremely rare to go (as I've been told).

    During repair found the PFC 474k 450v Film Cap at the input of the power supply was melted.
    After lots of help from others here - I found a suitable replacement.

    The 5vdc standby power has now been restored to the set, and the red standby light illuminates (problem solved).
    Progress.


    Which brings us to TODAY:

    The P/S is still producing very low or no output voltage during the power/on command.

    24v only generates about 18v before shutdown (3-4 secs.)
    18v only generates about 12v before shutdown
    12v only generates about 0.7v before shutdown

    Since there is a 5vdc standby being sent - and -
    a 5volt return signal from the CPU (power/on) command switch,
    I'm assuming that the problem still lies within the Power supply boards ability to generated the regulated voltages.

    Without an accurate diagram, theoretical application is only getting me so far.

    Anyone have any thoughts or ideas ???
    Attached Files
  • tom66
    EVs Rule
    • Apr 2011
    • 32560
    • UK

    #2
    Re: Polaroid PSU output power

    Since 12V is so low, I would check the diode for the 12V output, and see if it is shorted.
    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

    • kenny1070
      Senior Member
      • Oct 2013
      • 65
      • USA

      #3
      Re: Polaroid PSU output power

      Thanks for the help Tom66.

      I'm assuming the diode for the 12volt is the D118.
      I pulled it out and it tested good (about 750 & infinity).

      I also pulled out what assume is the 24volt (D117).
      It tested good as well.

      I may have to start pulling out the transistors.
      The upper casings where the screw hold downs are (to the heatsinks) appear to have melted. Not sure if that is actually affecting the integrity of the current flow.
      Nor am I sure which transistor is operating which leg of the supply.

      Any other help you could provide would be great,

      Thanks
      Attached Files

      Comment

      • kenny1070
        Senior Member
        • Oct 2013
        • 65
        • USA

        #4
        Re: Polaroid PSU output power

        Just found this on the D116.

        It is the flip side of the transistor on the right of the last picture highlighted.

        None of the others appear to be like this - they all have good clean solders.

        I'm not sure if this a factory designed bridge (?) - or the result of a power surge melting the solder into it.


        Any thoughts ???
        Attached Files

        Comment

        • kenny1070
          Senior Member
          • Oct 2013
          • 65
          • USA

          #5
          Re: Polaroid PSU output power

          Success !!!!


          That was it.

          I put a soldering wick on the bridge and eliminated it.

          Powered up the set --- and full function !


          A year and a half and 25 bucks later - it lives once again

          Thanks to everyone for helping.

          On to the next one

          Comment

          • keats11
            Senior Member
            • Nov 2012
            • 88
            • USA

            #6
            Re: Polaroid PSU output power

            I have a Polaroid FLM3201 I picked it up from CL this weekend with the same blue light symptom. Its is a power supply issue, and all the DC voltages are low. Instead of 24 V, I have 17. Instead of 12V I have 7 and Instead of 18V I have 13. I found the schematic that Tom had posted in one of the forums, but there aren't any voltages labelled in the schematic. Has anyone come across this issue? It seems to me the transformer T902 is not being driven hard enough to generate the full voltages necessary.

            Comment

            • tom66
              EVs Rule
              • Apr 2011
              • 32560
              • UK

              #7
              Re: Polaroid PSU output power

              Check if you have 450V across main cap.
              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

              • keats11
                Senior Member
                • Nov 2012
                • 88
                • USA

                #8
                Re: Polaroid PSU output power

                I don't, I onlyhave 150V across the main cap. Looking at the schematic, the cap seems to be connected to the output of a bridge rectifier, so I would have only expected 150V. There is some PFC circuit that seems to be connected in parallel to it, basically an inductor+FET that drives it, the inductor O/p is connected in parallel to the cap output. Is this somehow supposed to boost the voltage? Tom, what would be your next guess?

                Comment

                • tom66
                  EVs Rule
                  • Apr 2011
                  • 32560
                  • UK

                  #9
                  Re: Polaroid PSU output power

                  Correction should be 390V+/-10V, but either way it is bad.

                  You have a fault with the PFC section of PSU, so check around there. It involves a diode, inductor, MOSFET and controller IC, among other parts.
                  Last edited by tom66; 01-06-2014, 06:44 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

                  • xyloeye
                    Member
                    • May 2011
                    • 20
                    • USA

                    #10
                    Re: Polaroid PSU output power

                    I don't mean to hijack this thread, but I have the same problem in a Poloroid FLM323 that normally outputs only 24v. The 24v is present but plugging in the main board swamps the voltage down to 16v and the inverter supply goes to nearly zero. I think I've narrowed it down to the PFC also since the voltage across the big cap is only 170v. I'm wondering about a defective diode or maybe the PWM controller. I just got a couple of parts in and I'll report back if I figure anything out.

                    Comment

                    • xyloeye
                      Member
                      • May 2011
                      • 20
                      • USA

                      #11
                      Re: Polaroid PSU output power

                      Would the PFC boost voltage be that high (390) in the US where we start with 120VAC? tom66 is in the UK where it's 230VAC.

                      Comment

                      • budm
                        Badcaps Legend
                        • Feb 2010
                        • 40746
                        • USA

                        #12
                        Re: Polaroid PSU output power

                        It is the PFC Voltage booster (done by PFC Controller IC) that boost the DC out put to 370~400VDC range, without it the voltage on the filter cap will be only 170VDC (120VAC in), or 330VDC (for 30VAC in). That is why the cap is rated at 450VDC.
                        Last edited by budm; 01-08-2014, 04:34 PM.
                        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

                        • xyloeye
                          Member
                          • May 2011
                          • 20
                          • USA

                          #13
                          Re: Polaroid PSU output power

                          Oh, thanks, Bud. I didn't realize the boost was that much. I think I saw in another thread (could be mistaken) where you mentioned that the high voltage film cap is part of the 24v circuit. Is it necessary for proper function of the PFC?

                          Comment

                          • 13919
                            Member
                            • Jan 2014
                            • 11
                            • United States

                            #14
                            Re: Polaroid PSU output power

                            Great site, I just joined.Anyone know where the find a schematic with voltages for this power supply. ine is dead across the dotted line.

                            Comment

                            • 13919
                              Member
                              • Jan 2014
                              • 11
                              • United States

                              #15
                              Re: Polaroid PSU output power

                              Add I replaced all 6 of the 680uf caps because they were rounded on the top

                              Comment

                              • vinceroger69
                                Badcaps Legend
                                • Mar 2012
                                • 6714
                                • uk

                                #16
                                Re: Polaroid PSU output power

                                Originally posted by 13919
                                Add I replaced all 6 of the 680uf caps because they were rounded on the top
                                whats the exact power board numbers so we can see if we can find a schematic for it.

                                Comment

                                • 13919
                                  Member
                                  • Jan 2014
                                  • 11
                                  • United States

                                  #17
                                  Re: Polaroid PSU output power

                                  kas200-5s2418112xl

                                  Comment

                                  • 13919
                                    Member
                                    • Jan 2014
                                    • 11
                                    • United States

                                    #18
                                    Re: Polaroid PSU output power

                                    I guess my big question is what carries the voltage across the dotted line on the board. all the test points on the 110v side have power,everything on the slave side is dead.Looks like the only bridge components are a cap, a xformer. three tiny square thingies with 4 legs (technical term),and a coil.Trying to back trace to a dead part.

                                    Comment

                                    • vinceroger69
                                      Badcaps Legend
                                      • Mar 2012
                                      • 6714
                                      • uk

                                      #19
                                      Re: Polaroid PSU output power

                                      Originally posted by 13919
                                      kas200-5s2418112xl
                                      schematic i think.
                                      Attached Files

                                      Comment

                                      • budm
                                        Badcaps Legend
                                        • Feb 2010
                                        • 40746
                                        • USA

                                        #20
                                        Re: Polaroid PSU output power

                                        Your power supply is just like the one as shown in post 3?
                                        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

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