HP 1955 Monitor Repair Guide

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  • sermulis
    Member
    • Jul 2013
    • 38
    • Latvia

    #161
    Re: HP 1955 Monitor Repair Guide

    I got 29 V DC

    Comment

    • budm
      Badcaps Legend
      • Feb 2010
      • 40746
      • USA

      #162
      Re: HP 1955 Monitor Repair Guide

      Right at the two legs? It cannot be that high!, The IC will not take that, your meter's battery is good? It is 15V zener diode.
      Last edited by budm; 09-05-2013, 04:01 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

      • sermulis
        Member
        • Jul 2013
        • 38
        • Latvia

        #163
        Re: HP 1955 Monitor Repair Guide

        hmm. sometimes multimeter shows low battery indicator. measured one more time. same results. in 20 v range its out of range. will try to find another multimeter meanwhile.

        Comment

        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA

          #164
          Re: HP 1955 Monitor Repair Guide

          You need to change the battery.
          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

          • sermulis
            Member
            • Jul 2013
            • 38
            • Latvia

            #165
            Re: HP 1955 Monitor Repair Guide

            replaced battery. same results!

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA

              #166
              Re: HP 1955 Monitor Repair Guide

              Sorry to say, that cannot be, unless the Zener is open. As you can see in the circuit, that 15V Zener is for regulating the VCC for the SMPS IC to be at 15V max.
              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

              • sermulis
                Member
                • Jul 2013
                • 38
                • Latvia

                #167
                Re: HP 1955 Monitor Repair Guide

                I see.. is it wise idea replacing zener diode without going any further? may be mosfets Q602, Q603 are shortd too, as well as zener diode ZD602.

                p.s. sorry for spamming into forum. I am totally new in electric diagrams and repairs greater than simple cap replacing

                Comment

                • sermulis
                  Member
                  • Jul 2013
                  • 38
                  • Latvia

                  #168
                  Re: HP 1955 Monitor Repair Guide

                  on D602 i've got 10.9V

                  Sorry for measleading info. I measured standard diodes not zener ones.

                  Find proper ones

                  ZD601 - 10.2 V
                  ZD602 - 10.6 V
                  Last edited by sermulis; 09-06-2013, 04:21 AM.

                  Comment

                  • budm
                    Badcaps Legend
                    • Feb 2010
                    • 40746
                    • USA

                    #169
                    Re: HP 1955 Monitor Repair Guide

                    About 10VDC is correct voltage for NCP1200 SMPS IC to run. Check R615 Source resistor 0.22 Ohm for MOSFET Q601 to see if it is open. Check the DC voltage at the Drain pin of Q601 using C605 Negative leg as the ground ref point for this primary circuit section.
                    OK, just to sure, you are not getting any DC voltages on these caps?
                    Attached Files
                    Last edited by budm; 09-06-2013, 12:10 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

                    • Behemot
                      Badcaps Legend
                      • Dec 2009
                      • 4845
                      • CZ

                      #170
                      Re: HP 1955 Monitor Repair Guide

                      If there is NCP1200AP40, those are 40kHz version, hard to get. I just managed to buy 10 pcs so if anybody wants some…
                      Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

                      Exclusive caps, meters and more!
                      Hardware Insights - power supply reviews and more!

                      Comment

                      • sermulis
                        Member
                        • Jul 2013
                        • 38
                        • Latvia

                        #171
                        Re: HP 1955 Monitor Repair Guide

                        hmm. maybe i am doing smth absolutely wrong or problem is behind the power board? pinout differs on actual board versus schema. measurements was taken without logic board and lcd panel connected.
                        Attached Files

                        Comment

                        • budm
                          Badcaps Legend
                          • Feb 2010
                          • 40746
                          • USA

                          #172
                          Re: HP 1955 Monitor Repair Guide

                          OK, the power supply is not dead after all since you are getting the 5V, so next step will be hooking up logic board back but leave the flat cable from the logic board that go to the panel and see if those voltage readings change or disappear, especially the 5VDC. one thing does bug me is that you are getting only 13V for the inverter, but then the sch does not match your board 100%.

                          I will need you to post good closed up pictures of your board, both sides so I can trace out the connections and compare it to the sch.
                          Last edited by budm; 09-06-2013, 09:21 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

                          • Behemot
                            Badcaps Legend
                            • Dec 2009
                            • 4845
                            • CZ

                            #173
                            Re: HP 1955 Monitor Repair Guide

                            The inverter should be getting 13-13,5 volts, at least that's what inverter in my piece was fed with and worked OK.

                            Than there is transistor step-down for +3,3 V, probably to directly feed ICs on logic board.
                            Last edited by Behemot; 09-06-2013, 09:51 PM.
                            Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

                            Exclusive caps, meters and more!
                            Hardware Insights - power supply reviews and more!

                            Comment

                            • budm
                              Badcaps Legend
                              • Feb 2010
                              • 40746
                              • USA

                              #174
                              Re: HP 1955 Monitor Repair Guide

                              Can you tell me what voltage are you getting at those 4 locations?
                              Notes: number 4 location are 3 pins, report reading at those 3 pin with the monitor connected to running PC. One of those 3 pin is for BL_ON (Backlights ON), another pin is for Backlights Dimming control, the 3rd pin I do not know what that one is for.
                              Attached Files
                              Last edited by budm; 09-06-2013, 10:10 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

                              • Behemot
                                Badcaps Legend
                                • Dec 2009
                                • 4845
                                • CZ

                                #175
                                Re: HP 1955 Monitor Repair Guide

                                Yeah, may be all-in-one regulator, who knows…the thing is, if it works and gives +13something V, it should also give +3,3 to feed the logic board.
                                Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

                                Exclusive caps, meters and more!
                                Hardware Insights - power supply reviews and more!

                                Comment

                                • sermulis
                                  Member
                                  • Jul 2013
                                  • 38
                                  • Latvia

                                  #176
                                  Re: HP 1955 Monitor Repair Guide

                                  Originally posted by budm
                                  Can you tell me what voltage are you getting at those 4 locations?
                                  Notes: number 4 location are 3 pins, report reading at those 3 pin with the monitor connected to running PC. One of those 3 pin is for BL_ON (Backlights ON), another pin is for Backlights Dimming control, the 3rd pin I do not know what that one is for.
                                  if i understood you right.. than

                                  V1 - 3.3V
                                  V2 - 4.97V (pin to GND)
                                  V3 - 5.07V (pin to GND)
                                  V4 - from left to right - 3.13V, 0.02V, 0.02V (each pin to GND)

                                  Comment

                                  • sermulis
                                    Member
                                    • Jul 2013
                                    • 38
                                    • Latvia

                                    #177
                                    Re: HP 1955 Monitor Repair Guide

                                    After all came to conclusion that my Power supply board IS OK.
                                    Cut and repaired old sleeve from logic board to control buttons.
                                    Connected all cables back. Now i am not able to see any diode indicator lights on control menu (diodes are OK). Pressing power on button seems doesn't work (silent dead monitor state).

                                    May be someone can provide Logic board chema for this HP 1955 ?

                                    Comment

                                    • budm
                                      Badcaps Legend
                                      • Feb 2010
                                      • 40746
                                      • USA

                                      #178
                                      Re: HP 1955 Monitor Repair Guide

                                      Please post the pictures of the Logic board, both sides, so I can look for the SCH of your board version.
                                      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

                                      • sermulis
                                        Member
                                        • Jul 2013
                                        • 38
                                        • Latvia

                                        #179
                                        Re: HP 1955 Monitor Repair Guide

                                        Alright. Finally dealt with this monitor. After re soldering bad joints, and fixing cable to logic board, monitor came to life.

                                        Comment

                                        • holoprox
                                          New Member
                                          • May 2014
                                          • 2
                                          • Bulgaria

                                          #180
                                          Re: HP 1955 Monitor Repair Guide

                                          1-st post here

                                          48.L1A02.A31 board

                                          changed all capacitors 1000 mF 16->25V
                                          ,22 160V (gray ones) with ,22 400~

                                          resoldered most of the board
                                          checked ZD601

                                          is it safe to switch on?

                                          hoq to check Q805 and Q812? between S and D? @200ohm?

                                          Comment

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