64PN5500 | BN44-00618A Main fuse keeps popping

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  • nickgronk
    Member
    • Apr 2021
    • 32
    • Canada
    #1

    64PN5500 | BN44-00618A Main fuse keeps popping

    Power supply board BN44-00618A keeps blowing main fuse and nothing plugged in to it.
    I was gifted a 64PN5500AF, picture was amazing, but tv smelled like cigarettes and was dusty AF. I opened it up, blew all the dust out of it, removed PSB & main, and cleaned the metal underneath. Also blew all the dust off all other boards. Put the power supply back in, then mainboard. Soon as I turned it on there was a "pop".
    The main fuse (T12AH250V) blew
    I removed the power supply to be sure nothing underneath, all good. Soldered on a t12ah250v fuse and sure enough it popped again. Unplugged the mainboard and Y board - last fuse, it popped again.
    I've ordered more fuses, but what can be the issue?
    Tags: None
    • diif
      Badcaps Legend
      • Feb 2014
      • 6978
      • England
      #2
      Re: 64PN5500 | BN44-00618A Main fuse keeps popping

      There's usually a sheet of something under the power supply to stop it shorting on the back of the chassis, that's not fell off when you were cleaning has it ?
      Photos will help us to see.
      I think the model number is wrong, is it a PN64F5500AF ?

        Comment

        • nickgronk
          Member
          • Apr 2021
          • 32
          • Canada
          #3
          Re: 64PN5500 | BN44-00618A Main fuse keeps popping

          Yes you're right, it is a PN64F5500AF . There wasn't any sheet underneath, the risers are built into the sheet metal. Will take some pics of the PSB and get them posted
          Attached Files
          Last edited by nickgronk; 01-23-2022, 04:48 PM. Reason: more details

            Comment

            • dskall
              Badcaps Legend
              • Oct 2016
              • 2905
              • usa
              #4
              Re: 64PN5500 | BN44-00618A Main fuse keeps popping

              Unplugged and with main caps. discharged. Measuring across middle pins on bridge rectifier and across outer pins with multimeter on continuity should read open.
              Last edited by dskall; 01-23-2022, 04:52 PM.
              I assume no responsibility for any stupid suggestions I might post.

                Comment

                • nickgronk
                  Member
                  • Apr 2021
                  • 32
                  • Canada
                  #5
                  Re: 64PN5500 | BN44-00618A Main fuse keeps popping

                  Both bridge rectifiers taken out of circuit to be sure. Both are perfect,

                  • On a whim, I replaced with another fuse from another PS board (same t12), did not solder in the bridge rectifiers (so none on the board), screwed the board back down, plugged in and turned on. Fuse is ok. ...

                  • Soldered the bridge rectifiers back in. Did not mount the board, laid it on rubber mat. Powered on and "zap" went the fuse.
                  Last edited by nickgronk; 01-23-2022, 07:23 PM. Reason: did some testing.

                    Comment

                    • dskall
                      Badcaps Legend
                      • Oct 2016
                      • 2905
                      • usa
                      #6
                      Re: 64PN5500 | BN44-00618A Main fuse keeps popping

                      What were the ohms on outside pins?
                      I assume no responsibility for any stupid suggestions I might post.

                        Comment

                        • nomoresonys
                          Badcaps Legend
                          • Jan 2013
                          • 12095
                          • U.S.
                          #7
                          Re: 64PN5500 | BN44-00618A Main fuse keeps popping

                          Check, looks like NT801s, I believe it's the mov, it's green, looks like one of those blue ceramic capacitors but it's not a cap, located just right of where you plug the power cord in, check in diode mode, it should be open as in not beep and NOT read 000 which would mean short.

                            Comment

                            • nickgronk
                              Member
                              • Apr 2021
                              • 32
                              • Canada
                              #8
                              Re: 64PN5500 | BN44-00618A Main fuse keeps popping

                              Originally posted by nomoresonys
                              Check, looks like NT801s, I believe it's the mov, it's green, looks like one of those blue ceramic capacitors but it's not a cap, located just right of where you plug the power cord in, check in diode mode, it should be open as in not beep and NOT read 000 which would mean short.
                              diode mode : .011 out of circuit

                              took out of circuit - fuse from old board intact. (running out of ceramic fuses... lol)
                              Last edited by nickgronk; 01-23-2022, 09:06 PM.

                                Comment

                                • nomoresonys
                                  Badcaps Legend
                                  • Jan 2013
                                  • 12095
                                  • U.S.
                                  #9
                                  Re: 64PN5500 | BN44-00618A Main fuse keeps popping

                                  Is it a constant steady beep?

                                    Comment

                                    • R_J
                                      Badcaps Legend
                                      • Jun 2012
                                      • 9535
                                      • Canada
                                      #10
                                      Re: 64PN5500 | BN44-00618A Main fuse keeps popping

                                      Originally posted by nomoresonys
                                      Is it a constant steady beep?
                                      NT801s is a NTC thermistor, 11Ω is fine it does not read open.
                                      Last edited by R_J; 01-23-2022, 08:59 PM.

                                        Comment

                                        • nomoresonys
                                          Badcaps Legend
                                          • Jan 2013
                                          • 12095
                                          • U.S.
                                          #11
                                          Re: 64PN5500 | BN44-00618A Main fuse keeps popping

                                          Ok, thanks RJ, I thought it might be the mov because I didn't see the mov anywhere else, does this tv not have one?
                                          Last edited by nomoresonys; 01-23-2022, 08:56 PM.

                                            Comment

                                            • nickgronk
                                              Member
                                              • Apr 2021
                                              • 32
                                              • Canada
                                              #12
                                              Re: 64PN5500 | BN44-00618A Main fuse keeps popping

                                              Originally posted by nomoresonys
                                              Ok, thanks RJ, I thought it might be the mov because I didn't see the mov anywhere else, does this tv not have one?
                                              this board has the NT801s . I shlud follow up. unable to read which side is which and dont think it should matter... dunno. but testing the legs of NT801s one side read 11ohm, switched leads read OL

                                              EDIT: trying to remove the white goop, chip disintegrated.
                                              Attached Files
                                              Last edited by nickgronk; 01-23-2022, 09:24 PM.

                                                Comment

                                                • R_J
                                                  Badcaps Legend
                                                  • Jun 2012
                                                  • 9535
                                                  • Canada
                                                  #13
                                                  Re: 64PN5500 | BN44-00618A Main fuse keeps popping

                                                  Originally posted by nickgronk
                                                  this board has the NT801s . I shlud follow up. unable to read which side is which and dont think it should matter... dunno. but testing the legs of NT801s one side read 11ohm, switched leads read OL
                                                  It will read as a resistor, both ways. it is not the problem, check the mosfets mounted to the heatsinks, like QS802, QS804
                                                  and the pfc circuit mosfets like QP801c.
                                                  With no main board connected, it is likely the power supply is turning on all the circuits so a fault in any of them will blow the fuse.
                                                  Last edited by R_J; 01-23-2022, 09:26 PM.

                                                    Comment

                                                    • nickgronk
                                                      Member
                                                      • Apr 2021
                                                      • 32
                                                      • Canada
                                                      #14
                                                      Re: 64PN5500 | BN44-00618A Main fuse keeps popping

                                                      Originally posted by R_J
                                                      It will read as a resistor, both ways. it is not the problem, check the mosfets mounted to the heatsinks, like QS802, QS804
                                                      and the pfc circuit mosfets like QP801c.
                                                      With no main board connected, it is likely the power supply is turning on all the circuits so a fault in any of them will blow the fuse.
                                                      Found another NT801s from a spare board, tested good, soldered in and zapped another fuse. will test fets .

                                                      Thank you everyone for all of your help! #SundayFunday

                                                        Comment

                                                        • R_J
                                                          Badcaps Legend
                                                          • Jun 2012
                                                          • 9535
                                                          • Canada
                                                          #15
                                                          Re: 64PN5500 | BN44-00618A Main fuse keeps popping

                                                          NT801s is just a current limiter for when the power supply is in standby, It gets shorted out by the relay contacts when the power supply is turned on.

                                                            Comment

                                                            • dskall
                                                              Badcaps Legend
                                                              • Oct 2016
                                                              • 2905
                                                              • usa
                                                              #16
                                                              Re: 64PN5500 | BN44-00618A Main fuse keeps popping

                                                              Your problem will be on other side of bridge rectifiers. Probably fet.
                                                              I assume no responsibility for any stupid suggestions I might post.

                                                                Comment

                                                                • nickgronk
                                                                  Member
                                                                  • Apr 2021
                                                                  • 32
                                                                  • Canada
                                                                  #17
                                                                  Re: 64PN5500 | BN44-00618A Main fuse keeps popping

                                                                  Was both QS802 and QS804 - set is back online. Thanks a bunch!

                                                                    Comment

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