ViewSonic VX924 No power - Not the usual suspects

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • Player2
    Senior Member
    • Aug 2009
    • 98
    • USA

    #1

    ViewSonic VX924 No power - Not the usual suspects

    I am having a great time with ViewSonics this week

    I'm working on a VX924 which does not power on, nor does the green LED blink. I replaced all of the CrapXons (including the lil 100 uF and the large filter cap) on the power board, replaced the 4 transistors under the inverters, even replaced the ceramic caps by the inverters.

    For a while it was ticking when I applied power to it, sounded like it was going into protection. As I tested parts and started swapping components the ticking would come faster or slower. Now it does not tick at all and it still does not power up. The fuse is still good. I've got voltage at the main filter cap, but no 12v DC output.

    I'll get pics up today, but I think we all know what this board looks like Any suggestions?
  • PlainBill
    Badcaps Legend
    • Feb 2009
    • 7034
    • USA

    #2
    Re: ViewSonic VX924 No power - Not the usual suspects

    Originally posted by Player2
    I am having a great time with ViewSonics this week

    I'm working on a VX924 which does not power on, nor does the green LED blink. I replaced all of the CrapXons (including the lil 100 uF and the large filter cap) on the power board, replaced the 4 transistors under the inverters, even replaced the ceramic caps by the inverters.

    For a while it was ticking when I applied power to it, sounded like it was going into protection. As I tested parts and started swapping components the ticking would come faster or slower. Now it does not tick at all and it still does not power up. The fuse is still good. I've got voltage at the main filter cap, but no 12v DC output.

    I'll get pics up today, but I think we all know what this board looks like Any suggestions?
    The ticking sound indicates the SMPS is trying to start, but either the load is too great, or the running supply for the SMPS controller is not functioning.

    I'm not certain why you felt it necessary to replace the caps in the inverters. Most (all) I have examined have either a fuse or a jumper that can be lifted to disconnect the inverter.

    I am certain you are sure you soldered in the replacement caps with the proper orientation. Double check that. A cap in backwards was the cause of problems with one recap job I did.

    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

    • Elab
      New Member
      • Jul 2009
      • 2

      #3
      Re: ViewSonic VX924 No power - Not the usual suspects

      Check D660, D661 = MBR10100CT

      Comment

      • Player2
        Senior Member
        • Aug 2009
        • 98
        • USA

        #4
        Re: ViewSonic VX924 No power - Not the usual suspects

        D660 is definitely bad, didn't see a D661 though. Something else is still keeping it from coming on though. I'm going to work my way out from D660 and see what else could be affected.

        All of the caps are oriented correctly, double checked against a working board. I replaced the ceramics near the transformers based on a tip in another thread. It was a shot in the dark.

        Comment

        • Maugli
          New Member
          • Jun 2008
          • 5

          #5
          Re: ViewSonic VX924 No power - Not the usual suspects

          Player, I am working on the same problem. 12 volts is not stable. any progress on your end?

          Comment

          • EGuevarae
            Badcaps Legend
            • Nov 2008
            • 1336
            • USA

            #6
            Re: ViewSonic VX924 No power - Not the usual suspects

            Originally posted by Maugli
            Player, I am working on the same problem. 12 volts is not stable. any progress on your end?
            Post a pic of the board, so suggestions can be made.
            There are 10 kind of people in this world: those that understand binary, and those who don't.
            • ASUS ROG Maximus IX Code
            • Intel Core i5-7600K 3.8GHz
            • 16gb GSKILL TridentZ RGB DDR4-3200
            • 1 M2 SSD + 2 WD Blue 1TB (Mirrored)
            • Windows 10 Pro x64
            • GeForce GT1050
              2 x Acer KA240H + 1 Vewsonic VP2130 21 (a cap replacement job )

            Comment

            • wsqlim
              New Member
              • Aug 2010
              • 5

              #7
              Re: ViewSonic VX924 No power - Not the usual suspects

              I have "the blinking" power LED problem as well. After replacing all the capacitors, it still fail to power up, still blinking LED. I'm getting unstable 8-9DC on the power output side. What can be causing this and how to fix it?

              Comment

              • Dgtech
                E. Technician
                • Apr 2009
                • 1462
                • Steeler

                #8
                Re: ViewSonic VX924 No power - Not the usual suspects

                The last guy never posted pics of any of these boards. I'm hoping you will so that there may be a solution. Take pictures (front and back) of both PC boards. Post them as attatchments - no inline pictures. People will jump onboard quicker when there are pictures.
                The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

                Comment

                • wsqlim
                  New Member
                  • Aug 2010
                  • 5

                  #9
                  Re: ViewSonic VX924 No power - Not the usual suspects

                  I left the monitor alone for some time. Then I remembered 1 CAP 330uF 35V I replaced with 330uf 50V. So I got another 330uF 35V and put it in place. The monitor works, but only for 1 day. The next day I try to power up, I get the blinking light again.
                  Last edited by wsqlim; 03-22-2011, 11:48 PM.

                  Comment

                  • retiredcaps
                    Badcaps Legend
                    • Apr 2010
                    • 9271

                    #10
                    Re: ViewSonic VX924 No power - Not the usual suspects

                    Originally posted by wsqlim
                    So I got another 330uF 35V and put it in place. The monitor works, but only for 1 day.
                    What brand and series did you use for replacement? It matters because the SMPS requires low ESR caps like Panasonic FR capacitors.
                    --- begin sig file ---

                    If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

                    We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

                    Please do not post inline and offsite as they slow down the loading of pages.

                    --- end sig file ---

                    Comment

                    • blutch
                      Member
                      • Mar 2011
                      • 18

                      #11
                      Re: ViewSonic VX924 No power - Not the usual suspects

                      i also have a vx922 with fluctuating power from the 12v rail between boards. i have replaced all caps but the large 400v. still the power goes from 12v to 4v and repeats over and over. and the screen and green power light blink in time with it. what else could be the problem?

                      Comment

                      • retiredcaps
                        Badcaps Legend
                        • Apr 2010
                        • 9271

                        #12
                        Re: ViewSonic VX924 No power - Not the usual suspects

                        Originally posted by blutch
                        i also have a vx922 with fluctuating power from the 12v rail between boards. i have replaced all caps but the large 400v. still the power goes from 12v to 4v and repeats over and over. and the screen and green power light blink in time with it. what else could be the problem?
                        Cross posting is frowned upon here and confuses people and makes for more work. Keep your discussion contained to your thread at

                        https://www.badcaps.net/forum/showthread.php?t=13873
                        --- begin sig file ---

                        If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

                        We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

                        Please do not post inline and offsite as they slow down the loading of pages.

                        --- end sig file ---

                        Comment

                        • wsqlim
                          New Member
                          • Aug 2010
                          • 5

                          #13
                          Re: ViewSonic VX924 No power - Not the usual suspects

                          I took out the monitor and replace all caps again. It seems to be working, but something bothers me. The red circled heat sink feels very hot within minutes, while the blue circled one is stone cold. And I am hearing this faint rattling sound while power is on. And with power off I can hear faint beep sounds, even if I off the power supply but leave the power cord plug in, the sound still remains. Any1 can advise what seems to be the problem?
                          Attached Files

                          Comment

                          • retiredcaps
                            Badcaps Legend
                            • Apr 2010
                            • 9271

                            #14
                            Re: ViewSonic VX924 No power - Not the usual suspects

                            Originally posted by wsqlim
                            The red circled heat sink feels very hot within minutes, while the blue circled one is stone cold.
                            The picture is pretty tiny, but if the power mosfet is connected to that heatsink, that could be normal operation.

                            Look at the power mosfet part number, then find its datasheet. The datasheet might tell you on the operating temperature.

                            Same suggestion for the diodes on the blue heatsink. The diodes are responsible for your secondary voltages.

                            And I am hearing this faint rattling sound while power is on. And with power off I can hear faint beep sounds, even if I off the power supply but leave the power cord plug in, the sound still remains. Any1 can advise what seems to be the problem?
                            When the power cord is plugged in, 5V standby is always on.
                            --- begin sig file ---

                            If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

                            We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

                            Please do not post inline and offsite as they slow down the loading of pages.

                            --- end sig file ---

                            Comment

                            • wsqlim
                              New Member
                              • Aug 2010
                              • 5

                              #15
                              Re: ViewSonic VX924 No power - Not the usual suspects

                              Thanks for your advise retired, but I can't make out the number.

                              Well I have another working VX924, maybe I can open it and compare the two. But it does not have such noise while in operation. The repaired one makes this faint rattling sound while powered on, kind of like what a damaged fan will sound like. And is it normal for the beeping sound to be there?

                              Here's a bigger pic, if it helps. Thanks
                              Attached Files

                              Comment

                              • wsqlim
                                New Member
                                • Aug 2010
                                • 5

                                #16
                                Re: ViewSonic VX924 No power - Not the usual suspects

                                I think the heat problem is quite serious, I actually smell something burning after leaving the monitor on for 5 mins.

                                Comment

                                • jetadm123
                                  Badcaps Legend
                                  • Feb 2010
                                  • 2169

                                  #17
                                  Re: ViewSonic VX924 No power - Not the usual suspects

                                  If the one circled in red is silkscreened on the board as Q320, then it may be a NDF04N60ZG mosfet rated at 600V, 4.4A, 28W.

                                  Comment

                                  • pedro
                                    Senior Member
                                    • Dec 2009
                                    • 199
                                    • AUSTRALIA

                                    #18
                                    Re: ViewSonic VX924 No power - Not the usual suspects

                                    Originally posted by wsqlim
                                    I took out the monitor and replace all caps again.
                                    Can you remind us which brand/series caps you used?
                                    Friends don't let friends buy Samsung ....

                                    Comment

                                    Related Topics

                                    Collapse

                                    • DenK
                                      Acer Aspire 5 A514-55 - won't power on, no charger LED, battery not flat - usual suspects?
                                      by DenK
                                      Dear all, I am trying to troubleshoot an Acer Aspire 5 A514-55 that won't power on. I'll describe the symptoms and my findings so far, and I would like to seek guidance and suggestions on possible suspects in terms of cause/component failure. My initial thoughts are battery charger IC and/or ideal diode/MOSFET (that switches between incoming DC and battery power), but I could be totally wrong on this.
                                      1) Laptop was working fine on battery, then user realised battery was running low. Plugged in AC adapter but noticed it was not charging (LED on AC adapter plug did not light). Eventually shut down
                                      ...
                                      12-06-2024, 01:29 AM
                                    • RetroComputingGrotto
                                      Viewsonic VA2010wb (High Pitch Squeal At Power On)
                                      by RetroComputingGrotto
                                      I've got a monitor on my workbench at the moment that makes a high pitch squeal (that I cant hear as my ears are too old) when you power it on and lasts a couple of seconds before quitening and apparently it can be heard at regular intervals whilst on.

                                      On opening up the monitor and looking at the PCB the usual suspects showed their heads so I have already replaced all the electrolytic capacitors.

                                      The other issue that was reported with this monitor was the fact it took ages to start displaying anything after pressing the power button.



                                      What component(s)...
                                      02-03-2025, 06:00 AM
                                    • lostone
                                      Looking for help with a Viewsonic VP230mb where the backlight comes on only momentarily
                                      by lostone
                                      Hello, I came here after finding some similar questions asked on other monitors and hope someone here can help me get an ancient Viewsonic VP230mp (23" 4:3 LCD) back to working condition.

                                      First a little background, I have a background in computer and electrical engineering, and I'm smart enough to know I know nothing about LCD displays and how they work. For this topic I'm as green as they come.
                                      When the display is turned on the viewsonic logo displays in the uppper left for 2 seconds then the screen goes black, the power LED is green (on) and when a computer is connected...
                                      05-19-2024, 11:40 AM
                                    • mikey5791
                                      Tiny Tech ATX480W output power ticking
                                      by mikey5791
                                      Hi to all forum members,

                                      ​​​​​​This psu (Tiny Tech model ATX 480W) had been installed in a very old Windows XP PC but recently i pulled it out as the pc cannot start. To test it, i jumped the green wire and black wire on the 24 pin connector. The psu fan jerk a bit but not spinning. I used my dmm to check dc voltage on output connector wire, the 5v red wire keeps ticking a bit at around dc1v....then drops and ticking again around 1v. It is the same situation with the 12v yellow wire.

                                      Fyi, i desoldered the secondary side electrolytic cap those over 1000uf...
                                      02-20-2025, 01:11 AM
                                    • StefanNg
                                      Viewsonic VX2718-PC-mhd SG2701B01-8
                                      by StefanNg
                                      Hi, Badcaps.

                                      I am troubleshooting a monitor
                                      Viewsonic VX2718-PC-mhd.
                                      Panel model SG2701BSG2701-8
                                      Symptoms is no image.

                                      This panel has 2 panel board connected by a U-ribbon.
                                      When I disconnected the ribbon, I get a perfect half screen image.
                                      I took some test point voltage, when ribbon disconnected.
                                      HVAA 8.38v
                                      FVDD12 1.21v
                                      FDD33 3.3v
                                      VIN 11.79v
                                      VAA 16.85v
                                      VGHF 30.16v
                                      VGL -8.02v
                                      CK1_I ~ CK8_I 1.403v
                                      CK1_L ~ CK8_L 8.26v

                                      When I connect both panel board
                                      HVAA, VGHF, and CKx_L...
                                      05-17-2025, 01:43 AM
                                    • Loading...
                                    • No more items.
                                    Working...