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    #1

    Viewsonic VA702 LCD Monitor Sleep/Wake Problem

    I have a Viewsonic VA702 that would not turn on. I opened up and removed the power supply board and found someone else already replaced the 1000uf 25V cap (location C808), but there were 2 1000uf 10v and 3 220uf 25v caps that were buldging.

    I replaced the 2 1000uf 10v and the 3 220uf 25v caps and tested - now the monitor turned on properly. But once the monitor goes to sleep, it won't display an image again unless I unplug the monitor for a few minutes then it works again.

    If it goes to sleep, once I wake it up the LED turns green, looks like it thinks it's on, but the display is blank (BTW: the backlight is on, but display is a black/blank). If I unplug the monitor and wait a few minutes, it works again until it goes to sleep.

    Any ideas on this one?

    BTW: I found the service manual on the the VA702 if it helps
    Last edited by Rolin; 02-09-2012, 09:57 AM.
    Tags: None
    #2
    Re: Viewsonic VA702 LCD Monitor Sleep/Wake Problem

    Start easy - can we assume you have looked at this:

    If the monitor does not exit sleep mode when you move the mouse, there is a possiblity that the whole system, PC, went to sleep. Please check the power saving settings of your PC (Control Panel > Display > Screen Saver Tab > Monitor Power).

    Are you able to try it on another pc/laptop
    Please upload pictures using attachment function when ask for help on the repair
    http://www.badcaps.net/forum/showthread.php?t=39740

    Comment

      #3
      Re: Viewsonic VA702 LCD Monitor Sleep/Wake Problem

      Thanks for the reply. I should have mentioned that I'm a computer tech (actually I own a repair shop). We don't service monitors though, so I thought I would try to fix this one.

      I'm certain the computer is not at fault.

      Again, after the monitor wakes from sleep the power LED does turn green, it gets the signal from the computer but won't display anything more than a dark raster (backlight lit, but blank /black display) after waking up. Unplug power cord for a couple of minutes and plug back in - display works great until the monitor is put in sleep mode by pressing the front button - the LED turns yellow - press it again to turn on, LED turns Green and the display fails.

      Comment

        #4
        Re: Viewsonic VA702 LCD Monitor Sleep/Wake Problem

        1) Post clear focused top down view pictures of your power and main board following the instructions in my sig file below exactly.

        2) Do you have a multimeter and are you familiar with measuring DC voltages?
        --- 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 ---

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          #5
          Re: Viewsonic VA702 LCD Monitor Sleep/Wake Problem

          Thanks for your help. The pics are attached.

          I know how to use a multimeter, but I use it for basic functions more than anything. DC Voltages shouldn't be a problem. But for any advanced use, I might need a little help.
          Attached Files

          Comment

            #6
            Re: Viewsonic VA702 LCD Monitor Sleep/Wake Problem

            Originally posted by Rolin View Post
            The pics are attached.
            1) Those are excellent pictures. It makes a huge difference when I can read the pcb designations.

            2) Okay, I just wrote this today and bookmarked it. These are generic instructions, but I'm sure you can figure it out. Use a ground screw on the logic board for your black probe.

            Check U101 and U102 on the main/logic as per

            https://www.badcaps.net/forum/showpo...13&postcount=3

            I didn't circle it because I can see it so clearly.

            3) Measure U101 and U102 when it is working and when it is not working.

            4) Do the same for the multipin color connector on the power board. Use a ground screw on the power board for your black probe. When reporting these voltages, please list what the legend says since it is obscured in the photo.

            5) Obviously, we are looking for any differences in DC voltage when it is working and not working.
            Last edited by retiredcaps; 02-10-2012, 12:39 AM.
            --- 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

              #7
              Re: Viewsonic VA702 LCD Monitor Sleep/Wake Problem

              U101 = AS1117L-18 (1.8V)
              U102 = AS1117L-33 (3.3V)

              edit: The anti-capslock "feature" messed this post up and made it all lowercase.. again..
              Attached Files
              Last edited by Scenic; 02-10-2012, 01:02 AM.

              Comment

                #8
                Re: Viewsonic VA702 LCD Monitor Sleep/Wake Problem

                Heres what I measured:

                U101 working
                .3mv 2.407V 3.3445V

                U101 not working (after sleep)
                .3mv 3.473V 4.52V

                U102 Working and Not Working (same readings for the most part)
                .3mv 3.3V 5.20V

                Mulicolor connector on power board (cable connects to logic board)
                (NOTE: I measured on the power board side, but couldn't access the ground screw hole on the power board, so I used the ground screw hole on the logic board)
                Again, these readings were the same Working and Not Working

                1 VCC5V 5.2V
                2 VCC5v 5.2V
                3 Ground 7.7mv
                4 Brightness 3.29V
                5 on/off 5.10V
                6 ground 8.2mv

                Obviously the changes are noticed on the U101 chip. What do you think is causing this?
                Last edited by Rolin; 02-10-2012, 11:53 AM.

                Comment

                  #9
                  Re: Viewsonic VA702 LCD Monitor Sleep/Wake Problem

                  Originally posted by Rolin View Post
                  Heres what I measured:

                  U101 working
                  .3mv 2.407V 3.3445V

                  U101 not working (after sleep)
                  .3mv 3.473V 4.52V
                  U101 even when it is working is bad. The part number has a suffix -18 means the output voltage on pin 2 should be 1.8V DC +/- 1%. At 2.407V it is way too high.

                  Replacements are plentiful at your favourite distributor or local store. Any brand will do as long as the physical package fits. You may even find one on a junk board?

                  PS. Hmm, you report 4 digits. What kind of 4000 count multimeter do you have?
                  --- 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

                    #10
                    Re: Viewsonic VA702 LCD Monitor Sleep/Wake Problem

                    I looked online for AS1117L-18 and not having any luck. Read some other threads and found a few failures on this monitor and on what looks like an Acer equivilent monitor. Someone mentioned that digikey part number 497-6868-1-ND or LD1117S18CTR is the correct replacement. Is that true?

                    You mentioned these are plentiful - I have all kinds of motherboards, video cards, etc laying round - is there a cross reference that would tell me if I already have one by another part number? Or should I just order from digikey and wait for the part to arrive?

                    Thanks again for your help - really appreciate your time on this.

                    Comment

                      #11
                      Re: Viewsonic VA702 LCD Monitor Sleep/Wake Problem

                      Originally posted by Rolin View Post
                      I looked online for AS1117L-18 and not having any luck. Read some other threads and found a few failures on this monitor and on what looks like an Acer equivilent monitor. Someone mentioned that digikey part number 497-6868-1-ND or LD1117S18CTR is the correct replacement. Is that true?

                      You mentioned these are plentiful - I have all kinds of motherboards, video cards, etc laying round - is there a cross reference that would tell me if I already have one by another part number? Or should I just order from digikey and wait for the part to arrive?

                      Thanks again for your help - really appreciate your time on this.
                      The xx1117-nn family of regulators are 'jelly bean' parts - available from a number of manufacturers, functionally identical. Each manufacturer usus it's own two letter prefix, often part of the company name, or the company's numbering scheme. So yes, an AS1117L-18 is identical to a LD1117S18CTR. The important part is the 1117, 18 (the output voltage), and of course, the package.

                      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

                        #12
                        Re: Viewsonic VA702 LCD Monitor Sleep/Wake Problem

                        Yes that is an equivalent part.
                        Part nos and digikey nos are:
                        LD1117S18CTR
                        497-6868-1-ND = 1.8v



                        LD1117S33CTR
                        497-1241-1-ND = 3.3v

                        Whoops - started looking before lunch and posted after -!!
                        Last edited by selldoor; 02-11-2012, 07:09 AM. Reason: late again
                        Please upload pictures using attachment function when ask for help on the repair
                        http://www.badcaps.net/forum/showthread.php?t=39740

                        Comment

                          #13
                          Re: Viewsonic VA702 LCD Monitor Sleep/Wake Problem

                          I have found 1117-18 regulators some on pci sound cards (soundblaster) if you want to reuse.
                          --- 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

                            #14
                            Re: Viewsonic VA702 LCD Monitor Sleep/Wake Problem

                            Just wanted to update this thread so others would know the fix if they're facing the same problem. The U101 regulator AS1117L-18 replacement fixed the sleep problem. Now wakes up properly. Thanks for all the help on this one!

                            Comment

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