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    Viewsonic vx2252mh

    All,
    Have a Viewsonic vx2252mh that was recently tossed to the recyclers at work.

    The unit is a little over a year old according to the manufacturing tag on the back of the unit. So I grabbed it with a few other items that I have saved from the landfill\recyclers. Looks like the unit actually has a 3 year warranty.

    The Unit cosmetically is perfect and the protective plastic covering is actually still on the stand.

    The monitor lights the bottom clear bezel (blue) at the bottom of the monitor (power notification etc).

    The screen goes to a completely bright white screen (completely filled) (back lights I am assuming) and flashes the white screen on and off. Further assuming the back lights are just turning on and off.

    Then the bottom clear bezel turns orange and the flashing of the screen stops.

    Menu button does not work\Change the screen in any fashion.

    I have not tried to plug into a PC as of yet... but assume my fellow IT personnel tried it with a few PCs before tossing.

    No unusual sounds or smells...

    Seems to come apart easy enough (there goes warranty)... I am going to look at the common Capacitor issues/loose connections...but what would a standard set of troubleshooting steps be for this monitor or does anyone know or had this experience before with an LED monitor?


    Thanks for the help,
    Chris
    Last edited by SolomonMan; 01-28-2020, 07:10 PM.

    #2
    Re: Viewsonic vx2252mh

    Most monitor will go to sleep/hibernation if they don't see a video signal (orange light)
    Once you have it apart post some clear in focus picture of the boards, It may be as simple as a loose lvds cable (cable between main board and panel).

    Comment


      #3
      Re: Viewsonic vx2252mh

      Originally posted by R_J View Post
      Most monitor will go to sleep/hibernation if they don't see a video signal (orange light)
      Once you have it apart post some clear in focus picture of the boards, It may be as simple as a loose lvds cable (cable between main board and panel).
      I am hoping its something like that as its not that old and clean...

      Thanks
      Chris

      Comment


        #4
        Re: Viewsonic vx2252mh

        All,
        Unhooked and rehooked everything and still same result...no pic white screen.

        If I hook a db15 to the back of it...the orange light bezel light goes to blue and sits there with the white screen solid on.

        So I took it all the way down to the boards and rehooked everything so I could get some voltage readings...

        I have included my rough setup and readings in the images;

        Basically 36 volts to the Back Lights (I believe)....
        There are a pair of 5 volts and 3 volts connections (Lower Right)....

        On the Lower Left...I get a pair of 49.4 mv readings.

        All these readings are with the monitor plugged into a computer and power of monitor on...Clear Bezel is blue not orange...

        Any ideas?

        Thanks
        Chris
        Attached Files

        Comment


          #5
          Re: Viewsonic vx2252mh

          CN501 is just the plug for the blue and green audio jacks. CN701 pins 6&7 are +5 volts, pins 4&5 are ground, pin3 no connection, pins 1&2 are likely backlight control.

          Comment


            #6
            Re: Viewsonic vx2252mh

            Originally posted by R_J View Post
            CN501 is just the plug for the blue and green audio jacks. CN701 pins 6&7 are +5 volts, pins 4&5 are ground, pin3 no connection, pins 1&2 are likely backlight control.
            R_J,
            Thanks for the response.

            So looking over your response it appears the boards are the correct voltages but still there is no image or coloration on the screen....Any guesses on what is wrong with this monitor?

            I am not overly familiar with LED/LCD Monitors...Done a few cap/inverter replacements on TVs in the past...Is there a "Order of Operations" between the boards that could help troubleshoot?

            Thanks
            Chris

            Comment


              #7
              Re: Viewsonic vx2252mh

              Check if you have panel supply voltage (5v), It is likely on pin 18,19,20 of the lvds plug on the main board. If it is not there, check the voltages on U12, this is likely the panel voltage switch.
              Do you have a scope to check the if the lvds signal is present? If not you would need to try replacing the main board, then the panel.

              Comment


                #8
                Re: Viewsonic vx2252mh

                Originally posted by R_J View Post
                Check if you have panel supply voltage (5v), It is likely on pin 18,19,20 of the lvds plug on the main board. If it is not there, check the voltages on U12, this is likely the panel voltage switch.
                Do you have a scope to check the if the lvds signal is present? If not you would need to try replacing the main board, then the panel.
                R_J,
                So I did each pin on the lvds plug on the main board.

                Basically pins 28,29,30 are putting out the 5 volts.

                All the other pins except 7,14,17,24,25,26,27 on the lvds are putting out 1.38-1.4volts or close to that amount.

                The 7,14,17,24,25,26,27 pins are putting out 0.

                I found U12 on the main board it appears to be a single solder point...I originally got a reading of 0 volts... until I pressed the range on the meter a few times...it appears to be putting out a small 78.84 mv.

                All these readings are with the monitor plugged into a powered computer and monitor has a power source and of course monitor is on (blue Bezel).

                Unfortunately I do not quickly have access to a Oscilloscope...my step father has one but he's about 340 miles away from me (lives in Buffalo,Ny I am just North of Findlay Ohio) . I have been looking into one...but not sure if I should by a older one or a newer one...it was a recent discussion with the my step dad.

                Thanks
                Chris

                Comment


                  #9
                  Re: Viewsonic vx2252mh

                  Pins 28~30 on the lvds are the panel power, So it looks like the panel is getting power, The other pins supply the video/timing signals to the built in t-con board attached to the panel.
                  With a scope you would be able to see if there is video/data going to the t-con, I suspect the main board is working and the fault is on the t-con which is integrated to the panel.
                  U12 is the sot23-3 component just below the U12 marking. It connects to lvds pins 23~30 so I suspect it is working correctly. Have a look at the t-con board and provide a couple pictures of it, maybe there is a fuse located on it.
                  Last edited by R_J; 02-05-2020, 07:14 PM.

                  Comment


                    #10
                    Re: Viewsonic vx2252mh

                    R_J,
                    It appears there is a fuse (F1). Right above the 30 pin on the lvds connector.

                    Its a SMD and from continuity test it appears not to be continous (blown). Visibly it looks fine...maybe a single very small dot in the middle of the fuse but my magnifier glass does not really bring it out.

                    Also with everything plugged in as it should and power on there is also a 5V1 test point that is showing 5 volts but thats before the fuse.

                    With the fuse being probably bad the voltage readings outside (further right and left of the lvds connector) the fuse point not showing voltage lines up in my mind.

                    So the question is how do I proceed from here?

                    I have SMD\soldering station but have not done it ever...and I have no additional SMD fuses.

                    Is it probable the panel is just bad or is it possible the fuse just let loose?

                    Could I just solder over the fuse to test or do I risk irrepairable damage?

                    As always Open to ideas....

                    Thanks
                    Chris
                    Attached Files

                    Comment


                      #11
                      Re: Viewsonic vx2252mh

                      I should quickly mention the fuse was also tested by voltage readings...one side 5 volts the other not 5 volts....

                      Thanks
                      Chris

                      Comment


                        #12
                        Re: Viewsonic vx2252mh

                        Check the resistance between tcon ground and the fuse (the side without 5v) There is a cap,C5 that is not installed so you can use the negative pad for ground. There may be a short elsewere on the tcon that won't show itself right at the fuse, the short might be in the area of the (AUO) ic, sorted ic, shorted smd cap, diode, etc.

                        As for the fuse, there is likely a letter marked on it which is the value. It is possible that it is just the fuse that is bad.
                        I would not just "solder over" the fuse. you can solder a regular pigtail fuse (correct value) across it if you have one.

                        Also be carefull with the flex cables connecting the tcon to the panel, don't flex them or stress them to much. they are bonded and if they get damaged it is not good.
                        Last edited by R_J; 02-06-2020, 12:36 PM.

                        Comment


                          #13
                          Re: Viewsonic vx2252mh

                          Fuses come from any of the electronics places, Digikey and Mouser or there's ebay.

                          I'd put the widest tip on my iron and add leaded solder until its a ball that touches both sides of the fuse, at that point it should be free and stick to your iron when you remove it.
                          Last edited by diif; 02-06-2020, 12:21 PM.

                          Comment


                            #14
                            Re: Viewsonic vx2252mh

                            Originally posted by R_J View Post
                            Check the resistance between tcon ground and the fuse (the side without 5v) There is a cap,C5 that is not installed so you can use the negative pad for ground. There may be a short elsewere on the tcon that won't show itself right at the fuse, the short might be in the area of the (AUO) ic, sorted ic, shorted smd cap, diode, etc.

                            As for the fuse, there is likely a letter marked on it which is the value. It is possible that it is just the fuse that is bad.
                            I would not just "solder over" the fuse. you can solder a regular pigtail fuse (correct value) across it if you have one.

                            Also be carefull with the flex cables connecting the tcon to the panel, don't flex them or stress them to much. they are bonded and if they get damaged it is not good.
                            Again Thanks for the help!

                            Ok, so I set my Klein Tool Voltmeter to Ohm (sound) and put my negative black lead on the C5 Negative pad. I put the positive lead on one side of the fuse I get no sound...I do the same positive lead on the other side of the fuse and still nothing (no sound).

                            I did short tests across the capacitors on the TCON...nothing...

                            I tried enlarging my images of the TCON board, my eyes not as good as they used to be... to see if I see anything unusual...Nothing looks warm or unusual to my unskilled eyes.

                            I could do similar tests on the diodes and mosfets if you think it would be beneficial?

                            It seems like when I do voltage tests (somewhat difficult do to my current arrangement of the boards/cables) it does not get much outside the lvds cable area connnection of the TCON board. Can you tell from my previous scans whats controlling the propagation of voltage outside that area? Any other ideas?

                            Again thanks for the help,
                            Chris

                            Comment


                              #15
                              Re: Viewsonic vx2252mh

                              You can't do any voltage checks on the t-con with the fuse open, I would replace the fuse and see what happens, buy a few just in case.
                              When checking for shorts with your meter, don't rely on the Ohm (sound) use the low (usually 200Ω) range and note the resistance. If its not a short it should be ok. If you don't have a fuse, do you have something like a 1Ω 1/4 watt resistor? If you do, use it in place of the fuse for now.

                              Comment


                                #16
                                Re: Viewsonic vx2252mh

                                Originally posted by R_J View Post
                                You can't do any voltage checks on the t-con with the fuse open, I would replace the fuse and see what happens, buy a few just in case.
                                When checking for shorts with your meter, don't rely on the Ohm (sound) use the low (usually 200Ω) range and note the resistance. If its not a short it should be ok. If you don't have a fuse, do you have something like a 1Ω 1/4 watt resistor? If you do, use it in place of the fuse for now.
                                R_J,
                                Did the 1Ω 1/4 watt resistor route.

                                At first the Monitor just flashed the white screen as it did before.

                                I started using my hand to locate warm area on the TCON. Lower Left felt warm then fuse resistor started to smoke and then everything stopped...resistor toasted out. From quick test seems like things were powering up on the TCON board beyond the fuse then shutting down and then trying again over and over...The white screen did not sit consistently on as did before when plugged in to DB15 video source.

                                Tried again with new fuse resistor. Was able to locate warm area C9,C11,C12 and area around the ONV including possibly the ONV itself. C10 was an area not used just mount pads. The rest of the board never warmed up to the point I could feel anything unusual but did have voltage readings outside the LVDS connector where I did not previously. Upon touching C11 with leads the capacitor shifted off its pads. I shut things down...tried an attempt to put things back the way they were before. Tried things again C9,C11,C12 were again hot enough to shift again...so I shut it down to avoid further damage/future work.

                                Am I right in assuming something originally must have affected the panel on the left side and it just shorted out the TCON to the point it blew the fuse. My "replacing" the fuse shows us basically/roughly the troubled area but this is not a TCON issue but more than likely a Panel now as we are so close to the panel ribbon cable?

                                In either case I probably could clean the C9,C11,C12 up again, if you think its something in the TCON/worthwhile, but I would probably use my surface mount equipment.

                                I appreciate all the help...Please let me know I am really curious on your thoughts.

                                Thanks
                                Chris
                                Attached Files
                                Last edited by SolomonMan; 02-06-2020, 10:26 PM.

                                Comment


                                  #17
                                  Re: Viewsonic vx2252mh

                                  Check C9,11 & 12 with your Ω meter, do they check shorted? it is possible one is shorted, or the ic next to it is shorted.
                                  What is the number on the AUO ic?
                                  If it is the AUO ic, it will likely have a large solder pad in the middle used as a heatsink, so removal would not be easy and require a hot air station.
                                  Last edited by R_J; 02-07-2020, 10:32 AM.

                                  Comment


                                    #18
                                    Re: Viewsonic vx2252mh

                                    Originally posted by R_J View Post
                                    Check C9,11 & 12 with your Ω meter, do they check shorted? it is possible one is shorted, or the ic next to it is shorted.
                                    What is the number on the AUO ic?
                                    If it is the AUO ic, it will likely have a large solder pad in the middle used as a heatsink, so removal would not be easy and require a hot air station.
                                    R_J,
                                    Thanks again for the help!

                                    The AUO ic is a M201-2V 18151G.

                                    I do have a inexpensive hot air station....an ebay one...I use it commonly to remove IPad/Android digitizers. I do not have experience with removing and adding SMDs but I do have a few junk boards I could practice on if it came down to it. Not sure what more I would need other then flux, station, and solder.

                                    I tried your suggestion of not using the tone continuity/ohm tester portion of my multimeter to do my short tests but to try low ohm setting (200Ω)

                                    The value of the three capacitors matched at around 54-55 Ohms.

                                    I also did the tone test with the ground lead to ground and testing each capacitor sides. Checking for no two sides of a capacitor should set off the tone...Similar to the youtube video;

                                    https://www.youtube.com/watch?v=lpRgRDbhOPI

                                    The C9,11 & 12 all passed that test...Not sure if this test is even worthwhile let me know yout thoughts.

                                    One thing I did notice is with the tone no two side test that the "A" section of the board (On the left side of TCON but far right of "A" - C18,C16,C31) there were 3 capacitors which tested with no tone...but flipping the range did show high resistance reading on those three and they were consitent numbers (meaning each capacitor's sides had similar reading to each other...There was one in the "B" section (C25) that no toned and it roughly matched the sides of the other three capacitors in "A".

                                    Not sure if the above results (tone tests) means anything but if I could do it again I would clean an redo the C9,10,11 & 12 done to pads with new capacitors and replace the fuse (F1) as well. Not sure how to test that AUO ic (M201-2V 18151G) but maybe that as well?

                                    Thanks again for the help,
                                    Chris

                                    Comment


                                      #19
                                      Re: Viewsonic vx2252mh

                                      Most meters will "beep" checking continuity when the resistance is between 0Ω (or short) and 150Ω so all it tells you is there is a resistance less than 150Ω. In very low voltage circuits (1~3 volts) the dc resistance can be quite low.
                                      The caps are likely ok I suspect the ic is the problem but I don't see a datasheet on it
                                      I do see a few diodes and transistors in the area, I would check them also, They are easy to check and if found defective, easier to replace then the ic.
                                      Last edited by R_J; 02-08-2020, 10:40 AM.

                                      Comment


                                        #20
                                        Re: Viewsonic vx2252mh

                                        R_J,
                                        Again thanks for your help and knowledge transfer.

                                        I did the Diode Tests - Diode Mode;

                                        (Reading A) (Reading B)

                                        D1 - Not Used
                                        D2 - (2.072) (.688)
                                        D3 - (.212) (.393)
                                        D4 - 3 Legged
                                        D5 - 3 Legged
                                        D6 - (.208) (O-L)
                                        D7 - (.728) (O-L)
                                        D8 - Not Used
                                        D9 - (.703) (O-L)
                                        D10 - (1.238) (.692)
                                        D11 - 3 Legged

                                        3 Legged - I am not exactly sure how to measure these - but I went across each lead and flipped the probes and no set of leg tests on the 3 legged diodes had the same measurement when flipping the leads of the multimeter. Nor did they have O-L both ways...which I believe means they are good...Thats how I judged the Diodes. I believe this is the correct process on Diodes?

                                        This has been a great learning experience...but one question looking over the monitor boards I noticed the typical writing defining what each component on the board is....

                                        F - Fuse
                                        D - Diode
                                        C - Capacitor

                                        I have seen a couple that I am not familiar with...U, B, O, and I believe a T somewhere on the boards?

                                        U - looks to be ICs

                                        Is there a standard Legend on these identifiers?

                                        Thanks again,
                                        Chris

                                        Comment

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