CHIMEI CMV T38D - Buttons stopped working

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  • Agent24
    I see dead caps
    • Oct 2007
    • 4940
    • New Zealand

    #1

    CHIMEI CMV T38D - Buttons stopped working

    A while ago I replaced the capacitors in a Chimei CMV-T38D. I bought as faulty that it would turn off, getting quicker and quicker the longer it was on.

    It's been working fine ever since the new capacitors went in, but yesterday I found that all the buttons are dead (even power button). I am having such a good week!

    The power LEDs and speakers connect on the same board and they still work OK but the buttons do nothing.

    I reseated the ribbon cable at both ends but as I guessed this didn't change anything.


    What the heck would cause something like this?
    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
    -David VanHorn
  • Agent24
    I see dead caps
    • Oct 2007
    • 4940
    • New Zealand

    #2
    Re: CHIMEI CMV T38D - Buttons stopped working

    Today the buttons are working - in a way.

    All the buttons (except the 'Auto' button, which does nothing) now perform the function of the 'Auto' button - even the power button
    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
    -David VanHorn

    Comment

    • jetadm123
      Badcaps Legend
      • Feb 2010
      • 2169

      #3
      Re: CHIMEI CMV T38D - Buttons stopped working

      Photos would help. What brand/series of caps did you use for the initial recap?

      Comment

      • Agent24
        I see dead caps
        • Oct 2007
        • 4940
        • New Zealand

        #4
        Re: CHIMEI CMV T38D - Buttons stopped working

        Here's a picture of the PSU I took before I replaced the capacitors. I'll get some more photos later.

        I replaced them all with Panasonic FM and Nichicon HE except the little brown one which was Rubycon YXF I think.

        It's weird, because other than the button problem, the monitor still works perfectly.
        Attached Files
        "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
        -David VanHorn

        Comment

        • mockingbird
          Badcaps Legend
          • Dec 2008
          • 5484
          • -

          #5
          Re: CHIMEI CMV T38D - Buttons stopped working

          That's the same PSU as a ViewSonic VG2021m and Acer AL2017. Here is what I used to recap mine:

          C200 - 25v 220uF CAPXON KF Rubycon ZL 25V 220uF
          CE101 - 25v 220uF CAPXON KF Rubycon ZL 25V 220uF
          CE103 - 25V 1000uF CAPXON KF Panasonic FK 25V 820uF
          R100 - 25v 1000uF CAPXON KF Panasonic FK 25V 820uF
          CE105 - 10v 2200uF Panasonic FC 10V 2200uF
          CE104 - 10v 1000uF - TAICON PW - Nichicon PM 10V 1000uF
          CE108 - 220uF 25v - CAPXON KF Rubycon ZL 25V 220uF
          J100 - 50v 22uf - CAPXON GL Rubycon YXG 50V 22uF

          Comment

          • jetadm123
            Badcaps Legend
            • Feb 2010
            • 2169

            #6
            Re: CHIMEI CMV T38D - Buttons stopped working

            1) Is the pushbutton board the standard push switch type or the capacitive charge type (picture would help)?

            2) Have you examinined the pushbutton board and made sure there are no bad solder joints or shorts between the pins?

            3) Try checking the switch (assuming it's the standard mechanical pushbutton switch) with your DMM for the "auto" button. Maybe it or another switch is stuck in the closed position.

            4) Photo of the logic board would be good. Probably wouldn't hurt to check the voltage regulators on the logic board.

            Comment

            • Agent24
              I see dead caps
              • Oct 2007
              • 4940
              • New Zealand

              #7
              Re: CHIMEI CMV T38D - Buttons stopped working

              This is what I did with the capacitors:

              C200 - 25v 220uF CAPXON KF -> Panasonic FC 25V 220uF
              CE101 - 25v 220uF CAPXON KF -> Nichicon HE 25V 220uF
              CE102 - 25V 1000uF CAPXON KF -> Nichicon HE 25V 1000uF
              CE103 - 25V 1000uF CAPXON KF -> Nichicon HE 25V 1000uF
              CE104 - 10v 1000uF TAICON PW -> Panasonic FC 10V 1000uF
              CE105 - 10v 2200uF TAICON PW -> Nichicon HE 10V 2200uF
              CE107 - 50v 22uf CAPXON GL -> Rubycon YXF 50V 22uF
              CE108 - 25v 220uF CAPXON KF -> Nichicon HE 25V 220uF

              I used Panasonic FC for C200 rather than Nichicon HE as with CE101\CE108 because I had it left over, rather than any particular reason.

              jetadm123, here are the answers to your questions:

              1) Buttons are normal pushbutton types.

              2) Soldering is perfect, and they have worked perfectly previously

              3) DMM check shows all buttons to be working.

              4) Photos are attached as promised. What am I looking for RE: voltage regulators?


              There are Four SMD capacitors (electrolytic or polymer, I don't know) on the logic board. The last photo shows two values. One is 100uF 25v, the other 3 are all the other value, 47uF 25v. I do not know the brand or series. Should I replace these as well?
              Attached Files
              Last edited by Agent24; 11-28-2010, 05:37 PM.
              "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
              -David VanHorn

              Comment

              • kc8adu
                Super Moderator
                • Nov 2003
                • 8832
                • U.S.A!

                #8
                Re: CHIMEI CMV T38D - Buttons stopped working

                leaky button due to contamination or spill.
                resistor off tolerance

                Comment

                • mockingbird
                  Badcaps Legend
                  • Dec 2008
                  • 5484
                  • -

                  #9
                  Re: CHIMEI CMV T38D - Buttons stopped working

                  Originally posted by Agent24
                  This is what I did with the capacitors:
                  Don't expect to use incorrect series and get good results.

                  C200, CE101, CE108 - You used FC instead of Rubycon ZL. Other acceptable alternatives:
                  United Chemicon KZE; Panasonic FM; Nichicon HD
                  CE102, CE103 - You used Nichicon HE instead of Panasonic FK. Note that FK is a stretch in this situation, but the lowest ESR I could match given the dimensions.

                  Correct this and see if it resolves the problem.

                  Comment

                  • Agent24
                    I see dead caps
                    • Oct 2007
                    • 4940
                    • New Zealand

                    #10
                    Re: CHIMEI CMV T38D - Buttons stopped working

                    What is wrong with the replacements I used?

                    I checked the datasheets of both old and new to ensure the new had same or better specifications.

                    For example:
                    220uF 25v CapXon KF 550mA ripple and 0.15 Ohm ESR
                    vv replaced with vv
                    220uF 25v Panasonic FC 555mA ripple and 0.117 Ohm ESR
                    220uF 25v Nichicon HE 640mA ripple and 0.13 Ohm ESR.
                    Last edited by Agent24; 11-28-2010, 06:14 PM.
                    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                    -David VanHorn

                    Comment

                    • mockingbird
                      Badcaps Legend
                      • Dec 2008
                      • 5484
                      • -

                      #11
                      Re: CHIMEI CMV T38D - Buttons stopped working

                      I'm just quoting momaka, the truth is, I don't remember checking the specs myself:
                      Originally posted by momaka
                      The ESR of Rubycon MCZ is too low for PSU use, and the ESR of Nichicon VZ and NHG is too high.

                      For CapXon KM use any of the following: United Chemicon LXY, LXZ, KY; Panasonic FC; Nichicon PW, PM, HE; Rubycon YXG
                      For CapXon GL: United Chemicon KY; Panasonic FK; Nichicon PM, HE; Rubycon PX
                      For CapXon KF: United Chemicon KZE; Panasonic FM; Nichicon HD; Rubycon ZL
                      Most of these are available on Mouser and Digikey. Rubycon ZL, PX, and YXG are available at badcaps.net only.

                      Comment

                      • Agent24
                        I see dead caps
                        • Oct 2007
                        • 4940
                        • New Zealand

                        #12
                        Re: CHIMEI CMV T38D - Buttons stopped working

                        Hmm.. I guess yours will probably last longer than mine, but mine shouldn't be any worse than the originals as far as I can tell - I doubt they would cause any operation issues at least.

                        Originally posted by kc8adu
                        leaky button due to contamination or spill.
                        resistor off tolerance
                        With the ribbon cable to the button board unplugged, I get infinite resistance with the button off, and when pressed, less than 1 Ohm (As would be expected for a button)

                        Interesting though when the ribbon is plugged in:
                        All buttons (when pressed) show 22K Ohm except the 'Auto' button which shows 3.7K Ohm...

                        Since there are no resistors on the button board, I guess there is something going on with the logic board.
                        "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                        -David VanHorn

                        Comment

                        • jetadm123
                          Badcaps Legend
                          • Feb 2010
                          • 2169

                          #13
                          Re: CHIMEI CMV T38D - Buttons stopped working

                          My guess is that the power supply is good, since you're getting the 12V to drive the inverter section. 5V is probably good and we'll verify this by having you check the voltage regulator(s) output on the logic board. I've marked in the photo what I believe are the regulators (I can't read some of the part numbers). The large one is a 1.8V? 5A regulator. I can't read the part # on the smaller ones, but they're typically marked 1117.

                          I do agree with you that the problem lies between the push button board and the logic board.
                          Attached Files
                          Last edited by jetadm123; 11-28-2010, 08:26 PM.

                          Comment

                          • Agent24
                            I see dead caps
                            • Oct 2007
                            • 4940
                            • New Zealand

                            #14
                            Re: CHIMEI CMV T38D - Buttons stopped working

                            The four smaller ICs are marked:
                            58RP
                            N05A


                            The one in the middle:
                            AIC
                            1084-18PM
                            811CB
                            "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                            -David VanHorn

                            Comment

                            • jetadm123
                              Badcaps Legend
                              • Feb 2010
                              • 2169

                              #15
                              Re: CHIMEI CMV T38D - Buttons stopped working

                              Originally posted by Agent24
                              The four smaller ICs are marked:
                              58RP
                              N05A


                              The one in the middle:
                              AIC
                              1084-18PM
                              811CB
                              Not sure what the 58RP's are.

                              Try measuring the output of the 1084-18. I'm assuming that 18 is 1.8V. Use datasheet below for pin config.
                              Attached Files

                              Comment

                              • Agent24
                                I see dead caps
                                • Oct 2007
                                • 4940
                                • New Zealand

                                #16
                                Re: CHIMEI CMV T38D - Buttons stopped working

                                For the 1084-18 (U7) I measured 4.39v on VIN and 1.80v on VOUT.

                                The others are indeed 1117's. LM1117MPX-3.3 corresponds to N05A in the datasheet.

                                Measurements are:
                                U4: VIN 4.96v VOUT 3.29v
                                U5: VIN 4.96v VOUT 3.29v
                                U6: VIN 4.95v VOUT 3.29v
                                U8: VIN 4.97v VOUT 3.29v

                                That all seems to be OK I guess - Though maybe the input of U7 is a little low?
                                Last edited by Agent24; 11-28-2010, 09:30 PM.
                                "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                                -David VanHorn

                                Comment

                                • jetadm123
                                  Badcaps Legend
                                  • Feb 2010
                                  • 2169

                                  #17
                                  Re: CHIMEI CMV T38D - Buttons stopped working

                                  Originally posted by Agent24
                                  For the 1084-18 (U7) I measured 4.39v on VIN and 1.80v on VOUT.

                                  The others are indeed 1117's. LM1117MPX-3.3 corresponds to N05A in the datasheet.

                                  Measurements are:
                                  U4: VIN 4.96v VOUT 3.29v
                                  U5: VIN 4.96v VOUT 3.29v
                                  U6: VIN 4.95v VOUT 3.29v
                                  U8: VIN 4.97v VOUT 3.29v

                                  That all seems to be OK I guess - Though maybe the input of U7 is a little low?
                                  Output voltages look good. Have you tried taking voltage readings on the pushbutton board? Say, if you press one button, does the output voltage appear on any of the other push button outputs?

                                  Also, do we know that the ribbon cable connecting the logic and pushbutton is not internally shorted?

                                  Comment

                                  • Agent24
                                    I see dead caps
                                    • Oct 2007
                                    • 4940
                                    • New Zealand

                                    #18
                                    Re: CHIMEI CMV T38D - Buttons stopped working

                                    There doesn't seem to be any 'output' from the buttons (or I don't understand properly) One side connects to its own unique track and the other side goes to ground.

                                    I measured 3.1v across all buttons except the Auto button, which measures 0.86v.

                                    A ribbon cable doesn't seem to be the kind of thing that would short out internally to me. I'll check it after dinner though...
                                    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                                    -David VanHorn

                                    Comment

                                    • jetadm123
                                      Badcaps Legend
                                      • Feb 2010
                                      • 2169

                                      #19
                                      Re: CHIMEI CMV T38D - Buttons stopped working

                                      Originally posted by Agent24
                                      There doesn't seem to be any 'output' from the buttons (or I don't understand properly) One side connects to its own unique track and the other side goes to ground.

                                      I measured 3.1v across all buttons except the Auto button, which measures 0.86v.

                                      A ribbon cable doesn't seem to be the kind of thing that would short out internally to me. I'll check it after dinner though...

                                      You're probably right about the cable. Since there's no schematic, I not sure how the pushbutton board communicates with the logic board.

                                      However, it's interesting about the 0.86V on the auto button (maybe a short?) Would you be able to temporarily remove the auto button switch from the board to see it resolves the problem? Other than that, I've pretty much run out of ideas. Well, off to bed.

                                      Comment

                                      • Agent24
                                        I see dead caps
                                        • Oct 2007
                                        • 4940
                                        • New Zealand

                                        #20
                                        Re: CHIMEI CMV T38D - Buttons stopped working

                                        Yeah I'll try removing that button and see if it helps.

                                        I just realised why the buttons didn't do anything at all initially.
                                        It was because I was using the DVI input - and Auto Adjust doesn't do anything on digital signals.

                                        Since Auto Adjust is the only function which works currently, on a digital input, it wasn't enabled, so nothing happened at all!

                                        UPDATE: Removed the button, still the same problem. (All buttons only perform Auto Adjust feature)
                                        Still reading 0.86v on the pads where the button was, and 3.1v on the other buttons.
                                        Last edited by Agent24; 11-29-2010, 12:40 AM.
                                        "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                                        -David VanHorn

                                        Comment

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