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Acer AL2423W Recapped, backlight works but no display

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    #1

    Acer AL2423W Recapped, backlight works but no display

    Hi, I got a free Acer AL2423W LCD monitor from work, it was not working when I got it, there was nothing at all when I plugged in the power cable

    I changed these capacitors on the power board and after that the backlight turns on and is lit properly, at this stage the monitor draws 51w at the power socket.
    (Actually I cheated and did not replace the 10uF CapXon because I had problems removing the grounding shield, also I did not replace the 450v bulk filter cap next to it)

    Code:
    10uF	50v	CapXon KF
4,7uF	250v	CapXon KM
22uF	50v	CapXon KF
22uF	25v	CapXon GL
33uF	35v	CapXon GL (x2)
82uF	450v	CapXon KM
100uF  25v   CapXon KF (x2)
1000uF 16v   CapXon KF (x2)
    Code:
    Replacement Capacitors from Big Pope:
1 x 10uF  50V Samxon RS
1 x 4.7uF 250V Samxon RT
1 x 22uF  50V Samxon GF
1 x 22uF  25V Samxon RS
2 x 47uF  35V Samxon RS
2 x 100uF 25V Samxon GF
2 x 1500uF 16v Samxon GC
    The two 100uF 25v capacitors sit at CS13 & CS16
    Also I replaced 2x 1000uF 16v caps at position CS15 & CS14 with 1500uF caps
    At positions CS10, CS11 & CS12 where United Chemi Con KY 25v 680uF caps that looked fine so I did not replace those...

    So after these caps had been replaced the monitor turns the backlight on as soon as I give it power
    However there is no picture displayed, either with or without a VGA or DVI cable
    Also it is not possible to press any buttons, nothing happens, not even the standby button

    At this stage I left it alone for several months but now when I saw the other 3 threads on this monitor with the bad Teapo caps on the logic board I decided to replace those, even tho they looked fine on my monitor.
    However after removing them both their ESR and Capacitance was good (0.1 and 370uF respectively)
    I recapped it anyway with Samxon GC 470uF 16v caps, 8 in total
    I did not have a replacement for the 100uF 25v Teapo, however in circuit I measured it at 0.11ESR and 109uF

    At this stage there was no difference from before, but I tried something I had not done before
    A added the GPU-Z monitorinfo program in the startup folder and shutdown my computer, next I stated it up with the Acer, which gave no picture still.
    I waited untill the computer had finished loading and this is what I found when I connected back my Eizo LCD:



    Lastly I measured the voltage at the underside of the PCB in the attached picture, I saw 19v, 12v and 5v at the middle of the Power Schottky rectifiers legs at each specific secondary output in the image (i.e. left, middle, and right arrow respectively)
    If anyone has managed to read this far and would like to offer me some input on what to test next I would be very grateful!
    Attached Files
    Last edited by Per Hansson; 10-28-2015, 11:45 AM. Reason: Correction about bulk cap model
    "The one who says it cannot be done should never interrupt the one who is doing it."
    Tags: None
    #2
    Re: Acer AL2423W Recapped, backlight works but no display

    Originally posted by Per Hansson View Post
    So after these caps had been replaced the monitor turns the backlight on as soon as I give it power
    However there is no picture displayed, either with or without a VGA or DVI cable
    Just want to confirm that all you have is a white screen then with no display?
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      #3
      Re: Acer AL2423W Recapped, backlight works but no display

      Yup that is correct
      The black image seems uniform too
      "The one who says it cannot be done should never interrupt the one who is doing it."

      Comment

        #4
        Re: Acer AL2423W Recapped, backlight works but no display

        Originally posted by Per Hansson View Post
        Yup that is correct
        The black image seems uniform too
        Sorry, just to be more precise.

        It is all white screen, but with no graphics (not a black screen)?
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          #5
          Re: Acer AL2423W Recapped, backlight works but no display

          Hello! While we have not yet ruled out that the logic board could be bad, may I suggest you check to see if there is a blown pico fuse located on the circuit board connected to the LCD panel. This board (I forget what it's called) is located at the top and usually spans the entire width of the panel and is connected to the LCD display via a number of flat flex ribbon cables. This board may have metal or plastic shield over it.
          Last edited by jetadm123; 07-31-2010, 10:37 AM.

          Comment

            #6
            Re: Acer AL2423W Recapped, backlight works but no display

            I forgot to add that you may also want to reseat the ribbon cable(s) that connect this board to the logic board.

            Comment

              #7
              Re: Acer AL2423W Recapped, backlight works but no display

              retiredcaps; oh sorry misread your first post
              No, it is a black screen, i.e. it is not letting through any light (except what bleeds through the panel)

              jetadm123: I believe you are speaking about the backlight PCB?
              But since my backlight does come on properly can't we rule that out?
              "The one who says it cannot be done should never interrupt the one who is doing it."

              Comment

                #8
                Re: Acer AL2423W Recapped, backlight works but no display

                Originally posted by Per Hansson View Post
                retiredcaps; oh sorry misread your first post
                No, it is a black screen, i.e. it is not letting through any light (except what bleeds through the panel)

                jetadm123: I believe you are speaking about the backlight PCB?
                But since my backlight does come on properly can't we rule that out?
                Maybe a picture of the problem is warranted here since the two answers are seem to be conflicting? Even a video posted on youtube would help.

                Are you getting 2 seconds to black?
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                  #9
                  Re: Acer AL2423W Recapped, backlight works but no display

                  No, the panel stays on, the backlight is lit
                  But it is a black screen, i.e. the LCD is not letting through the backlight
                  I.e. it is the most black the LCD can produce if you understand?
                  (I can post a pic if you want but right now the LCD is in many pieces )
                  "The one who says it cannot be done should never interrupt the one who is doing it."

                  Comment

                    #10
                    Re: Acer AL2423W Recapped, backlight works but no display

                    If you can please post a photo of the entire back of the monitor with all boards mounted and connected, it might make more sense. Thanks!

                    Comment

                      #11
                      Re: Acer AL2423W Recapped, backlight works but no display

                      I believe jetadm123 was referring to the 'panel card'. This is part of the LCD panel. It has the connector the cable from the logic card plugs into. That does not appear to be the problem, usually when the fuse on it blows you get a 'white screen' problem.

                      The problem is unusual. This power supply is actually a dual supply with a 5 volts standby supply and 12 and 19 volt main supplies. The fact that you have all output voltages, backlights, and a black screen indicates that many functions of the logic card are working, but it's not processing video, nor is it responding to the buttons.

                      What is even more puzzling is what appears to be a hammer in the background of one picture. I sincerely hope that was not used to fix any problems.

                      The pictures of the logic card are clear, but taken at a sharp angle that limits their usefulness. I would appreciate if you could provide one taken from directly overhead. There are a number of what appears to be voltage regulators that should be identified and tested.

                      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: Acer AL2423W Recapped, backlight works but no display

                        Yes, PlaninBill is correct. Sorry, I missed the part where you initially said it was a white screen, then changed it to a black screen. My suggestion would only hold true for a white screen.

                        Comment

                          #13
                          Re: Acer AL2423W Recapped, backlight works but no display

                          Originally posted by jetadm123 View Post
                          If you can please post a photo of the entire back of the monitor with all boards mounted and connected, it might make more sense. Thanks!
                          I am sorry about my English, I understand it gets confusing
                          I assembled the monitor, attached is a picture of how it looks

                          Also I took a picture of it with my SLR in manual mode, I tried to match the colors as best as I could, it is actually very close to how it looks in reality;
                          (Note that this image never changes, I've left it connected for a few minutes and it always looks like this...)




                          Originally posted by PlainBill View Post
                          The problem is unusual. This power supply is actually a dual supply with a 5 volts standby supply and 12 and 19 volt main supplies. The fact that you have all output voltages, backlights, and a black screen indicates that many functions of the logic card are working, but it's not processing video, nor is it responding to the buttons.
                          Yes I agree, it is very hard to troubleshoot
                          Also don't forget the fact that I got EDID data through the DVI cable with GPU-Z as I showed in the first post...

                          Originally posted by PlainBill View Post
                          What is even more puzzling is what appears to be a hammer in the background of one picture. I sincerely hope that was not used to fix any problems.
                          Hahaha, no, it was not used to fix things
                          The logic and power supply combo metal box when installed the wrong way (so I can measure with a DMM) has too short cables, so the rubber end of the hammer was used for strain relief for the cables

                          Originally posted by PlainBill View Post
                          The pictures of the logic card are clear, but taken at a sharp angle that limits their usefulness. I would appreciate if you could provide one taken from directly overhead. There are a number of what appears to be voltage regulators that should be identified and tested.
                          Ok, I will deassemble the LCD again and take some better pictures, I will take pictures of both sides of the logic card

                          Thank you for your input guys!
                          Attached Files
                          "The one who says it cannot be done should never interrupt the one who is doing it."

                          Comment

                            #14
                            Re: Acer AL2423W Recapped, backlight works but no display

                            Originally posted by Per Hansson View Post
                            I am sorry about my English, I understand it gets confusing
                            There is nothing wrong with your English. I'm just trying to get a very precise understanding of the problem to eliminate certain things.
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                              #15
                              Re: Acer AL2423W Recapped, backlight works but no display

                              Ok, thank you, I think it was jetadm123 that was most confused by my wording tho

                              Just for kicks I used my old Konica KD400Z to try to make a movie, I was not expecting it to work and it didn't, turns out I have allot of dead pixels on my old trusty Konica aswell (Not that I didn't know already)
                              Note that these are taken in the exact same light enviroment as the pics from the SLR, at the same time also
                              Attached Files
                              "The one who says it cannot be done should never interrupt the one who is doing it."

                              Comment

                                #16
                                Re: Acer AL2423W Recapped, backlight works but no display

                                Originally posted by Per Hansson View Post
                                Ok, thank you, I think it was jetadm123 that was most confused by my wording tho
                                Your English will be better than my Swedish anyday.

                                Did you try testing the voltage regulators as PlainBill suggested? I believe they are the chips marked 1084.

                                What you are seeing with this monitor is similar to the issue I have with the Daytek (not resolved yet).
                                Last edited by retiredcaps; 07-31-2010, 01:01 PM.
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                                  #17
                                  Re: Acer AL2423W Recapped, backlight works but no display

                                  Thanks for the photos! I have the same problem with a Viewsonic that I've been working on. And by the way, your English is very good! Sometimes, what happens is that while I'm typing a reply, someone may have already posted a reply before me, which may lead to some confusion because some of the replies may be out of sequence. I'm hoping I make sense!

                                  Comment

                                    #18
                                    Re: Acer AL2423W Recapped, backlight works but no display

                                    Thanks for your nice comments guys
                                    I did some measurements now, I started the monitor with the PSU and logic board laying the wrong way around (components facing up) with a blanket under for short circuit protection
                                    I also connected the two PCB's ground planes together because I noticed that there was no continuity of the ground otherwise (Normally the metal box these two boards sit in would connect them together via itself so I felt it could be unsafe to start it without this connection...)

                                    I added text to the image posted here on badcaps, it shows what voltages I measured on the Mosfets
                                    There is a full resolution image of this picture without the text obscuring the view here: https://www.badcaps.net/forum/attach...1&d=1399820756
                                    I'm unsure if this is the correct PDF for the "1084" Mosfet, but maybe:


                                    Attached Files
                                    Last edited by Per Hansson; 05-11-2014, 09:06 AM. Reason: Offsite images uploaded due to problems with host
                                    "The one who says it cannot be done should never interrupt the one who is doing it."

                                    Comment

                                      #19
                                      Re: Acer AL2423W Recapped, backlight works but no display

                                      Originally posted by Per Hansson View Post
                                      I did some measurements now
                                      Hmm, I don't have enough experience to judge, but all the voltage regulators are AC 1084 0553AL, but the one closest (U13) to the power board measures significantly lower than the other 2????

                                      Now it is possible that is "normal" for this design.
                                      Last edited by retiredcaps; 07-31-2010, 04:48 PM.
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                                        #20
                                        Re: Acer AL2423W Recapped, backlight works but no display

                                        retiredcaps; Yes, I made the same observation
                                        I checked with two multimeters just to make sure, with my Fluke 113 TRMS meter in auto mode it went a little crazy, but I know it has problems auto sensing low voltages otherwise too (below 5v inside PC for example)
                                        But both it and my CHY17 showed roughly the same value

                                        I found this thread now, it shows some details of the logic boards controller chip
                                        I suspected it was a Genesis and this seems to confirm it (have not removed the heatsink from mine yet tho)

                                        But the PDF they link to is dead, however I managed to find it on Archive.org, so I attached it to this post...
                                        It mentions the controller chip has a serial interface, and also an x86 CPU
                                        So now I will try to connect to this and see what I get, but that will be a project for tomorrow, time is late in Sweden now



                                        CN3 which I marked out with voltages is probably a RS422 serial interface
                                        J1 on the right is probably JTAG
                                        Attached Files
                                        "The one who says it cannot be done should never interrupt the one who is doing it."

                                        Comment

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