Announcement

Collapse
No announcement yet.

Sylvania lc320ss2 LCD TV keeps blowing fuse

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    #81
    Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

    Hi,
    A little update.
    We saw some improvement today after installing the replacement transistor.
    For the first time this tv showed some signs of life.

    With the lightbulb connected, the TV would show signs of what I believe is right. It would turn the light bulb on and off continuously, the stand-by led would be on, and the panel's lamps would come on and off too. I'd get a variable voltage on the power FET's gate and on the output diodes I'm getting more appropriate voltages too.

    But when connected to the Variac (with the fuse installed instead of the lightbulb) and feed about 10VAC, it's still drawing above 2 amps and the voltage at the FET's gate is not switching.

    The whole primary side still gets warm as before.

    I was suspecting the opto-isolator IC but I replaced it with a good one (although different specs) and it didn't change a thing.

    I'll take a closer look at the zener diodes and some other components around the FET's gate again to see if I can spot something.

    Regards,

    Comment


      #82
      Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

      What happen if you slowly turn up the Variac beyond 10V?
      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


        #83
        Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

        At a low voltage of 10VAC, the circuit may not oscillate. The fact that you have brief standby power shows the circuit is probably OK. As budm says you need to increase it beyond that point. There comes a time when you just have to watch for smoke.
        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


          #84
          Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

          I agree, since you did see the LED and the panel light did come on, then it must have been Oscillating.
          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


            #85
            Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

            Hi gents,
            Let me begin by notifying you that we've just achieved SUCESS!

            Thank you for the explanation, It was a result of misinterpretation on my part of what I thought needed to be happening. I thought the TV would continue to draw more amps as I continued to increase the AC voltage, therefore I wasn't feeding it more than around 10VAC. Last time I tried (when I still had a defective component in the circuit) going beyond 10VAC it blew the fuse at about 20VAC.
            But this time, when after your inputs, I tried increasing the VAC the amps went up until I applied about 16VAC, or so, then dropped to less than 1 amp and the TV started working normally as I continued increasing the VAC to normal level.

            Thanks!
            Attached Files

            Comment


              #86
              Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

              It actually powered up at 16VAC?!
              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


                #87
                Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                Noted on that voltage in my library!. Great job fxing it. By the way, the ref circuits I provided, was it close to what you have on your board?
                It is good to have that Sencore.
                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


                  #88
                  Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                  @tom66, I meant to say that around 16ACV the tv went on stand-by (as seen indicated by the front LED), the current draw dropped, etc. Instead of continuing drawing current, when increasing the ACV input, without any signs of life due to power supply not switching.
                  After I saw the current draw dropped I continued increasing the voltage up to normal levels and operated the tv normally.

                  @budm, thanks. Yes that schematic looks very similar.
                  It would have been very difficult for me to get anywhere without the Sencore.

                  Comment


                    #89
                    Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                    I have the same television model. The tv stopped working while watching. No power. Fuse was blown. Replaced fuse. Pushed power button with no results. Checked fuse. Fuse was blown. Any suggestions on where to start exploring the problems. Heard that this symptom is often a bad bridge rectifier or mosfet. I'm a newbie at this so how would I check these? ....and thanks for the thread and the prints on here

                    Comment


                      #90
                      Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                      @mah481, if you read the whole thread, you will find the answer. Hard to do it all over again with over 80 threads already.
                      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


                        #91
                        Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                        I just got one of these TVs with the same problem, dead and a blown fuse. So far I've found Q600, Q601, D604 and D607 shorted. I read thru the whole thread but did not see your bad components called out except for the transistors, also do you have part #'s for D604 and D607 as I assume those were bad for you too?

                        Comment


                          #92
                          Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                          Can someone help me make sure I find the correct replacement parts? There's schematic in post 73 that has a similar design and has part #'s that appear to be the same, at least for the diodes.

                          D604 has a 27B on it and is identified as MTZJT-7727B which is obsolete and digikey says its a 25.6v but all they have is a 27v
                          http://www.digikey.com/scripts/DKSea...67820539714999

                          D607 Marked with a 4148, found the 1N4148 replacement.

                          Q600 has a K10A500 or K10A50D marking

                          Q601 has marking
                          C
                          5344
                          Y111

                          Appreciate any help!

                          Made some corrections above, still looking for Q601 I think I got the rest..
                          Last edited by kevinm34232; 02-18-2013, 12:16 PM.

                          Comment


                            #93
                            Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                            Ok I found list of parts:

                            D604 = DIODE ZENER 27BSB-T26 - NDTB027BST26
                            D607 = SWITCHING DIODE 1SS133(T-77) - QDTZ001SS133
                            Q600 = FET MOS TK10A50D - QFWZTK10A50D
                            Q601 = TRANSISTOR 2SC2120-Y(TE2 F T) QQSY2SC2120F

                            The only thing Im sure of ordering is Q600 which happens to be out of stock, but the others I can't seem to find exact replacements for. Can you experts help me out here?

                            Comment


                              #94
                              Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                              D607? (http://www.ebay.com/itm/370405149675)
                              Q601? (http://www.ebay.com/itm/370487155952)

                              Comment


                                #95
                                Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                                Look OK to me.....
                                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


                                  #96
                                  Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                                  Ok last question is a match for D604 27BSB I think this is data sheet

                                  Comment


                                    #97
                                    Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                                    Oh also the S/M shows the 1SS133 part (http://www.mouser.com/Search/Product...755-1SS133T-77)

                                    But the actual diode had a 4148 printed on it (http://www.mouser.com/Search/Product...lkey512-1N4148)

                                    Are these 2 compatible and any advantage to either one?

                                    Comment


                                      #98
                                      Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                                      Looks right to me.
                                      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


                                        #99
                                        Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                                        Yes can't find a match for the 27BSB would the 27v diode work (http://www.mouser.com/Search/Product...771-NZX27X-133)
                                        as the datasheet shows the original diode around 25v.?

                                        Comment


                                          Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

                                          Is it on the gate of the fet?
                                          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

                                          Working...
                                          X