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    viewsonic va2231wm cannot power on

    Last Saturday, I power on my PC and monitor(buy at year 2010) at afternoon about 3.00pm. Then at midnight (12.00am) because I want continue download file, so I keep the PC running and set "power plan" in windows 7 to turn off display after 1 min not activate. (This is what I do normally for so many year and all the time it work well.

    I think about 3.00am midnight, suddenly I hear some "pop" sound but because I still sleeping, I though some other sound rather than this so I not wakeup for it.
    Next day I only found out the monitor death already which no light at power indicator then I try with other power cable and a also plug to other wall power to make sure the problem is monitor rather than other.

    Then I open the monitor, I see all the component are ok in vision. Nothing burn nor leak as show in photo. (Those white things is not leak right?)

    Then I check a fuse which show in photo, it write on board that it is T3.15A /250VAC , I use meter to check it and it is open so confirm fuse blow already. I tried to replace a fuse but sunday no shop so I tried with fuse that I have which is only 2A 250VAC so I try soldering it parallel to the broken fuse. Then I try to power it after put all the board back to chase. When I switch power on power cord, it blow the fuse.

    *I not even got chance to press the on button on monitor. I just power on from wall power it already blow.

    Next day I go buy the fuse which is T3.15AL 250VAC(It is glass fuse, not same as ceramic fuse which is use in board)
    This one after I solder it parallel and try to power on. This time also pop then I off the power. That time another pop sound come out. This also I not even press the on button on monitor yet, just power on from wall power.

    I open and check again, from vision all the board still ok and still cannot see anything burn out or leak, no burn smell at all.

    Really don't know what part become bad/spoil.

    Hope someone can tell me how to check and how to fix it.
    Thanks.

    There are 2 board and I only upload the power board(call main board?)
    Here got front view and back view, then for front, I also upload a few with bigger view but split into portion. The front and back should be correct as we normally view things in flip left right rather than flip top bottom.
    Attached Files

    #2
    Re: viewsonic va2231wm cannot power on

    You have a dead short if the fuse blows.
    Instead of a fuse you should use an incandescent lamp of say 60w to 100w.
    If it becomes bright when you plug the monitor in you have a short: disconnect it!

    But you don't need to do that now since we know there is a short, so better find it.
    With a multimeter measure between the AC legs, marked ~ & ~ on the attached components photo. (It's the bridge rectifier)
    If you see a short remove it.
    If not measure the two other legs marked + & -
    If you see a short remove it and measure it out of circuit, still a short? Then replace it...
    Finally with the bridge rectifier out of circuit measure the now empty spots on the board, still a short? Well keep looking until you find the other shorted components
    Attached Files
    "The one who says it cannot be done should never interrupt the one who is doing it."

    Comment


      #3
      Re: viewsonic va2231wm cannot power on

      1 more thing, early thread I forget to mention when that time got 2 pop sound which when power on from wall it pop then I off the power it pop again, that one, after that I check the fuse (T3.15AL 250VAC) it not blow, it still ok.

      Comment


        #4
        Re: viewsonic va2231wm cannot power on

        so if when I put fuse (T3.15AL 250VAC) and it not blow, will this still consider dead short?
        Anyway I had follow your instruction to check that bridge rectifier first.

        I am newbie for this things so I will write out more clearly so that you can see whether I done it correctly or not.

        First I check AC legs at there. (Which is middle of 2 legs in these 4 legs) I set diode at meter, it show 1(so it is "open" right? when I touch 2 probes together it will show number 002 plus buzz sound)

        Then I put red probe to + and black probe to - it still show 1.

        I just check some video on website how to check/test bridge rectifiers.
        I put red probe on - while black to AC legs, it show 596 and 594 for that 2 legs. Then while I put red probe on - and black probe on +, it show 1417(Is this normal? They say should in between 300-700 but this 1417, is it because it in board and I have to take it out from board to check again?).

        I put black probe on + and red probe to AC legs, it show 598 and 607.

        Is that ok to just connect this power board to wall power and then switch on to check bridge rectifiers? or too danger cause still don't know what will blow up?

        Comment


          #5
          Re: viewsonic va2231wm cannot power on

          The bridge rectifier seems to check ok,(it is just 4 diodes in one case) Next check Q804, It should not have a short between the center leg and the other two legs.
          There are also 8 other diodes (like D803, D804 etc.) on that board you should also diode test, they could read 200-600 one way and close to open the other way

          You need to find what is shorted, connecting power to the board will just result in another blown fuse.
          Last edited by R_J; 10-23-2018, 11:10 AM.

          Comment


            #6
            Re: viewsonic va2231wm cannot power on

            Originally posted by R_J View Post
            The bridge rectifier seems to check ok,(it is just 4 diodes in one case) Next check Q804, It should not have a short between the center leg and the other two legs.
            There are also 8 other diodes (like D803, D804 etc.) on that board you should also diode test, they could read 200-600 one way and close to open the other way

            You need to find what is shorted, connecting power to the board will just result in another blown fuse.
            But second time my when I put correct fuse which is T3.15A, it not blow even got 2 pop sound out when switch wall power. I check the fuse, it still ok so I cannot do like other people which is connect the power to this power supply board only then check the voltage come and out?

            Comment


              #7
              Re: viewsonic va2231wm cannot power on

              If the fuse is not blowing any more I suspect Q804 OR C808 IS shorted and now R815 is open circuit It should read 0.43Ω
              And now you may have also damaged components on the fet driver board CN803.
              Last edited by R_J; 10-23-2018, 07:45 PM.

              Comment


                #8
                Re: viewsonic va2231wm cannot power on

                Originally posted by R_J View Post
                If the fuse is not blowing any more I suspect Q804 OR C808 IS shorted and now R815 is open circuit It should read 0.43Ω
                And now you may have also damaged components on the fet driver board CN803.
                thanks.

                ok here is the result.
                zd801 637
                d802 473
                d803 539
                zd803 472
                d806 399
                d804 399
                d808 104
                d807 102
                d809 103

                For Q804, the component is 09N65GX FET.
                When I check D and S short, check other(G-D,G-S) no short.

                C808 short

                R815 nearly 0.6M Ω (is not0.43Ω)so is open right?
                dunno how to check CN803 and hard to see the thing inside there.

                Any suggestion?
                Last edited by gerbercage; 10-25-2018, 02:53 AM.

                Comment


                  #9
                  Re: viewsonic va2231wm cannot power on

                  Originally posted by R_J View Post
                  If the fuse is not blowing any more I suspect Q804 OR C808 IS shorted and now R815 is open circuit It should read 0.43Ω
                  And now you may have also damaged components on the fet driver board CN803.
                  do I need to solder out all of these to check again?

                  Comment


                    #10
                    Re: viewsonic va2231wm cannot power on

                    Remove Q804 and check it out of circuit to see if it is still shorted, then you can recheck C808, it is likley ok but check that it is not cracked or burnt. R815 is open and will need to be replaced. Hopefully you can replace Q804 and R815 and it will work.
                    Those other diodes seem to be ok, the lower readings on d807-9 are because they are schottky type (lower voltage drop)
                    Last edited by R_J; 10-26-2018, 11:26 AM.

                    Comment


                      #11
                      Re: viewsonic va2231wm cannot power on

                      Originally posted by R_J View Post
                      Remove Q804 and check it out of circuit to see if it is still shorted, then you can recheck C808, it is likley ok but check that it is not cracked or burnt. R815 is open and will need to be replaced. Hopefully you can replace Q804 and R815 and it will work.
                      Those other diodes seem to be ok, the lower readings on d807-9 are because they are schottky type (lower voltage drop)
                      Sorry for long delay.
                      Recently got something to do so I late reply.
                      I had remove the Q804 out and check it and it still D and S short.
                      C808 open/OL. (I think is bad, I dunno I check the capacitor correctly or not)

                      R815 open.

                      The Q804 is 09N65GX, I dunno whether I can find a replacement or not.
                      If I cannot find exactly the same, what should I find to replace it? I search in internet I think something like FMA09N65GX TO-220F? Dunno can find or not.

                      For C808, it is ceramic capacitor R 101K 1KV. I don't know the "R" got what meaning. I search in internet for this capacitor and I found something like this:
                      101K 100pF 1KV K ±10% Y5P RoHS Taiwan
                      As long as I can get 101K 1KV ceramic capacitor, it should be ok right?

                      If I able to get all these 3 and replace it, do I need to connect all to test? or I just connect power to power board then power on and see all ok or not before connect all power board to main board to test?

                      Comment


                        #12
                        Re: viewsonic va2231wm cannot power on

                        Originally posted by R_J View Post
                        Remove Q804 and check it out of circuit to see if it is still shorted, then you can recheck C808, it is likley ok but check that it is not cracked or burnt. R815 is open and will need to be replaced. Hopefully you can replace Q804 and R815 and it will work.
                        Those other diodes seem to be ok, the lower readings on d807-9 are because they are schottky type (lower voltage drop)
                        If I able to get all these 3 and replace it, do I need to connect all to test? or I just connect power to power board then power on and see all ok or not before connect all power board to main board to test?

                        Comment


                          #13
                          Re: viewsonic va2231wm cannot power on

                          Originally posted by R_J View Post
                          Remove Q804 and check it out of circuit to see if it is still shorted, then you can recheck C808, it is likley ok but check that it is not cracked or burnt. R815 is open and will need to be replaced. Hopefully you can replace Q804 and R815 and it will work.
                          Those other diodes seem to be ok, the lower readings on d807-9 are because they are schottky type (lower voltage drop)
                          I go a few shops already but can't find these part.

                          The Q804 is 09N65GX, it is very hard to find it. I even search in internet(digikey/mouser)
                          If I cannot find exactly the same, what should I find to replace it? I search in internet I think something like FMA09N65GX TO-220F?
                          Can you tell me what should I find for replacement? I can't even find this datasheet for it.

                          Then for resistor 0.43ohm, the shop ask me how many watt? how can I find out?

                          C808 is R 101K 1KV, one shop got 100pF but the capacitor only write out "100" at there rather than write out 101K 1KV, I ask the seller, she not even know what is 1KV, she say this is 100pF, so this one can use? I though that 1KV also important for it.

                          After replace, can I test the power supply board with power in first but not connect it the board to main board?

                          I hope someone can help me on this.
                          Thanks.

                          Comment


                            #14
                            Re: viewsonic va2231wm cannot power on

                            After this several week and go to a few shop. I can't find out these components.
                            The resistor 0.43ohm, none of the shop that I visit got it. The nearest value that they got are 0.4 and 0.47ohm. (Can I use it? should use 0.4 or 0.47?) How do I know what is the watt for that resistor?

                            For the Capacitor C808 is R 101K 1KV, one shop got it but label as "100" only, they don't even know whether is 1KV or what. (Can I use this one even without knowing whether is 1KV or not?)

                            For Q804, the mosfet 09N65GX, I also cannot find it. I check 9N65 datasheet at internet.





                            https://alltransistors.com/mosfet/tr...ansistor=19460
                            Although all refer to same thing but I don't know why got some different for each
                            Such as Gate-Source Voltage:some is ±30v while another is ±20v
                            Total Dissipation: some 167w, some 125w

                            So for this Mosfet that use in monitor, which criteria/value are more important when I finding a replacement?

                            Maximum Drain-Source Voltage |Vds|: 650 V (The replacement must higher than 650V or lower than 650V?
                            Maximum Gate-Source Voltage |Vgs|: 30 V (This must 30V? 20 or 40V can?)
                            Maximum Drain Current |Id|: 9 A (Replacement must higher than 9A right?)
                            Maximum Drain-Source On-State Resistance (Rds): 0.85 Ohm (Replacement must lower than 0.85 ohm right?)

                            Hope someone can give opinion on this.
                            Thanks

                            Comment


                              #15
                              Re: viewsonic va2231wm cannot power on

                              For the capacitor 101 = 100pf; 100 = 10pf so you should find one with 101, it is a ceramic type and needs to be 1kv because of the high voltage pulse so either 1kv or 2 kv
                              here are a couple from digikey
                              445-15889-ND 100pf 2kv
                              445-16009-ND 100pf 1kv
                              The resistor is likely a 1 watt film type flame proof
                              RSMF1JTR430TR-ND .43 ohm 1 watt
                              If you want to try a resistor try either the .4 or the .47 both are likley close enough to try.
                              for the fet
                              Vds should be higher
                              Vgs should be higher
                              Id should be higher
                              Rds should be close or a bit lower is ok
                              and remember it is a to220 all plastic case

                              Fuji site might help https://www.fujielectric.com/product...s/600_700.html
                              Last edited by R_J; 11-23-2018, 11:48 AM.

                              Comment


                                #16
                                Re: viewsonic va2231wm cannot power on

                                Originally posted by R_J View Post
                                For the capacitor 101 = 100pf; 100 = 10pf so you should find one with 101, it is a ceramic type and needs to be 1kv because of the high voltage pulse so either 1kv or 2 kv
                                here are a couple from digikey
                                445-15889-ND 100pf 2kv
                                445-16009-ND 100pf 1kv
                                The resistor is likely a 1 watt film type flame proof
                                RSMF1JTR430TR-ND .43 ohm 1 watt
                                If you want to try a resistor try either the .4 or the .47 both are likley close enough to try.
                                for the fet
                                Vds should be higher
                                Vgs should be higher
                                Id should be higher
                                Rds should be close or a bit lower is ok
                                and remember it is a to220 all plastic case

                                Fuji site might help https://www.fujielectric.com/product...s/600_700.html
                                ok thanks, I will try to find those.
                                Most of the site got delivery charge and due to I only want to buy 3 of these components so the delivery cost more than these 3 components. I may try to find some other that got free delivery.

                                Comment


                                  #17
                                  Re: viewsonic va2231wm cannot power on

                                  You may want to order 2 or 3 of each just in case you have a problem.
                                  Also when you go to try it you can place an incandescent 60-100 watt lamp (at your countries voltage) in series with the a/c cord. If there is a short the light will light bright. if things are ok the light will come on dim for a few seconds and fade out, and the power supply should operate.
                                  If the cap is not shorted and does not look cracked it is likely ok
                                  Last edited by R_J; 11-27-2018, 10:50 AM.

                                  Comment

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