HP L1702 goes on and off

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  • PCBONEZ
    Grumpy Old Fart
    • Aug 2005
    • 10661
    • USA

    #41
    Re: HP L1702 goes on and off

    CapXon KM are General Purpose [GP].
    To compare GP caps look at the Ripple Current ratings

    Other series of CapXon are rated near FC or even FM so if you have any you will need to look up the data sheets for those.
    It's not uncommon to have a few high grade caps mixed in with GP caps for specific apps on a PCB.

    I would attach the KM data sheet but file size limit is too low here.
    [Gezz, the file is only ~196k.]

    CapXon's site is hard to search but you can look up their data sheets with creative use of Google.
    Example for KM series: Put this into Google > site:capxongroup.com KM < as so:

    http://www.google.com/#hl=en&q=site%...fp=Q5rYJf3FIq4

    If you need to find a different series just change "KM" to the series you want the data sheet for.

    Even though KM are general purpose I would upgrade to something that is at least a basic grade of low ESR which you'll know because data sheet at least shows ESR in the table.
    Reason is the caps are much better and cost difference is usually nil.
    .
    Mann-Made Global Warming.
    - We should be more concerned about the Intellectual Climate.

    -
    Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.

    - Dr Seuss
    -
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    -

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    • PCBONEZ
      Grumpy Old Fart
      • Aug 2005
      • 10661
      • USA

      #42
      Re: HP L1702 goes on and off

      If you compare Ripple for the KM to FC and FM in the 1000uF 6.3v from earlier you can easily see how widely specs vary between caps.

      KM = 430 mA
      FC = 755 mA
      FM = 1290 mA
      .
      Mann-Made Global Warming.
      - We should be more concerned about the Intellectual Climate.

      -
      Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.

      - Dr Seuss
      -
      You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
      -

      Comment

      • Qwertyco
        Member
        • Apr 2009
        • 18

        #43
        Re: HP L1702 goes on and off

        Well, here I am back to square one!
        3a pico fuse is fine, checked soldered connections on the board and re-flowed quite a few.
        Plugged it all in and . . . . . . There is LIGHT!, and windows, and my desktop, then, flicker and gone again!
        Back lights come on for between 2 and 30 seconds, gently flickering all the time then go off again.
        Right back to where I started.

        ps. the only cap i DIDN'T change was the big boy!

        the screen just stayed on for about two minutes this time.
        Last edited by Qwertyco; 05-16-2009, 06:02 AM.
        "Life is like a Dancing Monkey - Pretty amusing, until it starts to lob faeces at you"

        Comment

        • EGuevarae
          Badcaps Legend
          • Nov 2008
          • 1336
          • USA

          #44
          Re: HP L1702 goes on and off

          Originally posted by Qwertyco
          ps. the only cap i DIDN'T change was the big boy!
          Rarely Fails. You probably have a bad lamp in there. Did you notice any strange noise when the lamp flickered?
          There are 10 kind of people in this world: those that understand binary, and those who don't.
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          • Qwertyco
            Member
            • Apr 2009
            • 18

            #45
            Re: HP L1702 goes on and off

            It seems to be Ok for two or three seconds, then off go the lights, no flickering or noise.

            Occasionally it stays on for a minute or two, gently flickering, then goes off, still no noise.
            "Life is like a Dancing Monkey - Pretty amusing, until it starts to lob faeces at you"

            Comment

            • Bobdee
              Badcaps Veteran
              • Jun 2008
              • 461

              #46
              Re: HP L1702 goes on and off

              Originally posted by Qwertyco
              It seems to be Ok for two or three seconds, then off go the lights, no flickering or noise.

              Occasionally it stays on for a minute or two, gently flickering, then goes off, still no noise.
              Hello again
              I agree with Eguevarae that its probably a bad lamp
              This link is a good read its not your monitor but still applies
              https://www.badcaps.net/forum/showpo...&postcount=296
              One to four will help you find out if its top lamps or bottom,but read whole link to get a good understanding of inverter problems

              replacing lamps is not that hard but very good care is needed
              bob

              Comment

              • EGuevarae
                Badcaps Legend
                • Nov 2008
                • 1336
                • USA

                #47
                Re: HP L1702 goes on and off

                Originally posted by Qwertyco
                It seems to be Ok for two or three seconds, then off go the lights, no flickering or noise.

                Occasionally it stays on for a minute or two, gently flickering, then goes off, still no noise.
                See this post on this very same thread.
                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

                • Qwertyco
                  Member
                  • Apr 2009
                  • 18

                  #48
                  Re: HP L1702 goes on and off

                  This may seem strange, but it seems to be getting better by itself!
                  I've seen it working fine for over an hour now, no flickering, no problems at all.
                  It still looses the backlights, but the time period before this happens is massively improved.
                  . . . and I haven't done anything to it lately!
                  "Life is like a Dancing Monkey - Pretty amusing, until it starts to lob faeces at you"

                  Comment

                  • PCBONEZ
                    Grumpy Old Fart
                    • Aug 2005
                    • 10661
                    • USA

                    #49
                    Re: HP L1702 goes on and off

                    Electrolytic caps can 'come and go' like that before they finally croak so you might not be home-free.

                    On the other hand...
                    There is characteristic of electrolytic caps that people don't talk about much anymore.
                    Electrolytic caps used to be called "self healing capacitors".
                    Ripple Currents damage the oxide layer [that is the actual dielectric] more or less by making pits (thin spots) in the layer.
                    Time also takes it's toll. [next paragraph]
                    Applying DC voltage [in the correct polarity] rebuilds [makes thicker] that oxide layer and refills the pits.
                    It works the same way as electroplating something only we are plating out an oxide.
                    [Note: In electroplating the solution is also called the Electrolyte. It's the same process.]

                    The oxide layer on caps that haven't been used [no DC applied] thins over time by dissolving into the electrolyte. [Shelf life issue.] As long as the electrolyte isn't shot the layer can be rebuilt through a process called "reforming". Reforming is basically applying a DC voltage in the correct polarity and increasing it incrementally until it's slightly higer than the rated voltage. [No, I dunno specific values, just how the process works.]
                    - Some of your caps your may be reforming to some degree. [Especially if this thing has been sitting in a closet for a couple years.]
                    But, don't count on that being a permanent fix unless you've fixed the other problems.
                    .
                    Last edited by PCBONEZ; 05-18-2009, 05:52 AM.
                    Mann-Made Global Warming.
                    - We should be more concerned about the Intellectual Climate.

                    -
                    Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.

                    - Dr Seuss
                    -
                    You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
                    -

                    Comment

                    • Qwertyco
                      Member
                      • Apr 2009
                      • 18

                      #50
                      Re: HP L1702 goes on and off

                      Originally posted by PCBONEZ
                      Electrolytic caps can 'come and go' like that before they finally croak so you might not be home-free..
                      Thats very interesting.

                      Could it be that the new Caps I fitted have been lying on the shelf for a long time, and are now 'Waking Up' ?

                      The person I got it from claimed it worked fine, but he hadn't used it for a while.

                      It does seem to keep going for longer and longer between blackouts.
                      "Life is like a Dancing Monkey - Pretty amusing, until it starts to lob faeces at you"

                      Comment

                      • Qwertyco
                        Member
                        • Apr 2009
                        • 18

                        #51
                        Re: HP L1702 goes on and off

                        Quick update:
                        gentle flicker on first startup last night, then performed faultlessly for two hours before I switched it off !
                        "Life is like a Dancing Monkey - Pretty amusing, until it starts to lob faeces at you"

                        Comment

                        • Qwertyco
                          Member
                          • Apr 2009
                          • 18

                          #52
                          Re: HP L1702 goes on and off

                          Originally posted by Qwertyco
                          Quick update:
                          gentle flicker on first startup last night, then performed faultlessly for two hours before I switched it off !
                          I now declare this monitor FIXED!
                          running faultlessly.
                          Still not sure why it got better and better, unless it was the 'self repairing' caps thing!
                          Thanks for all your help guys!
                          I've been inspired now, I have two more monitors to attempt repair now,
                          Time for a new thread I think . . . . .
                          "Life is like a Dancing Monkey - Pretty amusing, until it starts to lob faeces at you"

                          Comment

                          • EGuevarae
                            Badcaps Legend
                            • Nov 2008
                            • 1336
                            • USA

                            #53
                            Re: HP L1702 goes on and off

                            Originally posted by Qwertyco
                            I now declare this monitor FIXED!
                            running faultlessly.
                            Still not sure why it got better and better, unless it was the 'self repairing' caps thing!
                            Thanks for all your help guys!
                            I've been inspired now, I have two more monitors to attempt repair now,
                            Time for a new thread I think . . . . .
                            Go for it! We're help to help or give you ideas.
                            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

                            • alsim
                              New Member
                              • Sep 2009
                              • 1

                              #54
                              Re: HP L1702 goes on and off

                              Hey, Thanks for Pic# 1 posted by Qwertyco.
                              That is the same board as my monitor. I needed to identify resistor R125. Mine was burnt and couldn't see all the color bands in order to replace it. Your Pic was perfect.
                              Last edited by alsim; 09-03-2009, 08:07 AM. Reason: add persons name

                              Comment

                              • Maxxarcade
                                Badcaps Veteran
                                • Jul 2006
                                • 973

                                #55
                                Re: HP L1702 goes on and off

                                Well, let me add another one to the mix. HP 1702 LCD... Backlight only comes on for about 1 second. I've replaced all caps and checked solder joints to no avail. Both lamps seem to be coming on, but could they still be the problem? I only paid $25 for the monitor, but i was hoping the toasted caps would be the only problem...

                                I think my boards are different than other I've seen in previous posts.





                                Attached Files

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                                • dobber
                                  Senior Member
                                  • Jul 2008
                                  • 83

                                  #56
                                  Re: HP L1702 goes on and off

                                  Ok, So I got a L1702 in and it gets video and loses it like everybody else. So I change out all the caps, and find that it is still doing the same thing. So I was asking at work, and found that one of our Slot Techs has one and it has the same issue after all the caps were changed. Is there a posability that they may have a bad Transformer on them causing this problem, or is there another route I should take.

                                  Comment

                                  • eckertb83
                                    Senior Member
                                    • Jan 2011
                                    • 71
                                    • United States

                                    #57
                                    Re: HP L1702 goes on and off

                                    Originally posted by dobber
                                    Ok, So I got a L1702 in and it gets video and loses it like everybody else. So I change out all the caps, and find that it is still doing the same thing. So I was asking at work, and found that one of our Slot Techs has one and it has the same issue after all the caps were changed. Is there a posability that they may have a bad Transformer on them causing this problem, or is there another route I should take.
                                    Mine is doing the same after re capping the board (all caps) and the backlight.
                                    What else is there to check?
                                    Sorry to bring up an old thread, but seemed better that starting a new one.

                                    Thanks for the help

                                    Comment

                                    • jetadm123
                                      Badcaps Legend
                                      • Feb 2010
                                      • 2169

                                      #58
                                      Re: HP L1702 goes on and off

                                      Originally posted by eckertb83
                                      Mine is doing the same after re capping the board (all caps) and the backlight.
                                      What else is there to check?
                                      Sorry to bring up an old thread, but seemed better that starting a new one.

                                      Thanks for the help
                                      The fact that it "loses video" is rather vague. Please give a more detailed description of the symptoms. Does it power off after a few seconds, or after several minutes? Does the power led and backlights stay on, but no video? Is it completely dead after it loses video? Asking us to second guess what you're seeing usually results in no help. More info only helps us help you.

                                      Several different power supplies were used on this monitor and good focused photos of your entire power supply (top and bottom shots) and logic board are required for members to point out things for you to check. Use the manage attachment button to post your photos.

                                      Comment

                                      • eckertb83
                                        Senior Member
                                        • Jan 2011
                                        • 71
                                        • United States

                                        #59
                                        Re: HP L1702 goes on and off

                                        Ok sorry about that mine does not lose video. Monitor comes on then a few seconds the screen goes black. If i hold a flash light to the screen i can see everything. I've all ready recapped the inverter board and new backlights. The led stays on and green. I will post pics shortly as I have to take it apart again.

                                        Comment

                                        • alexanna
                                          Member
                                          • Mar 2010
                                          • 1346

                                          #60
                                          Re: HP L1702 goes on and off

                                          Would you also see if you can read the number of the 16 pin IC on the back left side of the board.And on the connector going to the logic board , are any pin voltages identified?
                                          Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

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