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Acer AL2416W Power supply problem

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    #1

    Acer AL2416W Power supply problem

    Hi to all, I'm Emanuele, from Italy. first of all i want to say i found this forum absolutely amazing

    I immediately explain my problem. I was reading in this forum some posts about the Acer AL2416w because i was trying to repair the mine and i was doing some measurements with my DMM on the power supply board to test if it was all ok.

    ...but because i'm a noob i made the stupid mistake of try to measure the voltage across the pins 2-3 of the K3568. The result was that my ups restarted so i thought that i broke some components.

    Effectively the fuse F1 results bad (made continuity test) and obviously if before i measured 305 volt vdc across the main capacitor 450v/100uf now i measure 0. so i think that the component k3568 went bad (and i dont know if and/or what others components). so my question is..

    do you think i can repair the board and then proceed to the inverter and repair finally the monitor or i must throw all away? I hope someone can help me!

    PS: i attached a photo of the board with the components' indications as you can see. the board in photo is not exactly the mine one (i found that photo in another post and modified it because i dont have a good camera) but it's exactly the same board.

    PPS: sorry if my english is bad! :/
    Attached Files
    Last edited by lele.v; 09-18-2012, 04:41 PM.
    Tags: None
    #2
    Re: Acer AL2416W Power supply problem

    Originally posted by lele.v View Post
    so i think that the component k3568 went bad (and i dont know if and/or what others components).
    1) The datasheet is here

    http://pdf1.alldatasheet.com/datashe...SK3568_09.html

    2) With power off and lcd unplugged, you want to measure the resistance between pins 1-2, 1-3 and 2-3. If you have a manual range multimeter, set it to 200 ohms.

    3) A good fuse should measure less than 1.0 ohms.

    4) BD1 is a bridge rectifier. See if it shorted. With power off and lcd unplugged, you want to measure the resistance between pins 1-2, 1-3, 1-4, 2-3, 2-4 and 3-4. If you have a manual range multimeter, set it to 200 ohms.

    5) Report all the above results.

    PS: i attached a photo of the board with the components' indications as you can see. the board in photo is not exactly the mine one (i found that photo in another post and modified it because i dont have a good camera) but it's exactly the same board.
    Ideally, we would like to see a picture of your board because we have some eagle eyed members here that can spot potentially more damage.

    PPS: sorry if my english is bad! :/
    Your english is fine. It is 100% better than one recent poster who lives in the USA and doesn't use periods, punctuation or paragraphs. For those types of posts, I refuse to even read them and move onto the next post.
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    Comment

      #3
      Re: Acer AL2416W Power supply problem

      2) for the k3568:
      1-2: 117 ohm
      1-3: 117 ohm
      2-3: 0.7 ohm

      3) i think the fuse is definitely bad. with dmm set to 200 ohm the display returns "1 . " (if i'm not wrong this means infinite resistance, right?)

      4) assuming 1 to the left and 4 to right (where the + sign is) the results are:

      1-2: "1 . "
      1-3: "1 . "
      1-4: from 1 ohm to 0.8 ohm after some seconds
      2-3: "1 . "
      2-4: "1 . "
      3-4: "1 . "

      Comment

        #4
        Re: Acer AL2416W Power supply problem

        Originally posted by lele.v View Post
        2) for the k3568:
        1-2: 117 ohm
        1-3: 117 ohm
        2-3: 0.7 ohm

        3) i think the fuse is definitely bad. with dmm set to 200 ohm the display returns "1 . " (if i'm not wrong this means infinite resistance, right?)

        4) assuming 1 to the left and 4 to right (where the + sign is) the results are:

        1-2: "1 . "
        1-3: "1 . "
        1-4: from 1 ohm to 0.8 ohm after some seconds
        2-3: "1 . "
        2-4: "1 . "
        3-4: "1 . "
        2) Remove k3568 from the board and retest pins 2-3 out of circuit to see if the readings change.

        3) Your fuse is bad. "1" on the left hand side of a manual range multimeter means "out of range".

        4) Retest BD1 pins 1-4 once k3568 is removed. If it still reads 0.8 ohms, remove BD1 and retest pins 1-4 out of circuit.
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        Comment

          #5
          Re: Acer AL2416W Power supply problem

          ok. there is any particular method to desolder these kind of component with all that heatsink?

          Comment

            #6
            Re: Acer AL2416W Power supply problem

            Ideally you want the largest solder tip you can find. I have a 3.2mm chisel tip for desoldering stuff like that. If you can't remove it, try just to lift either pin 2 or pin3.

            "In circuit" readings are not reliable so k3568 could be good and something else on the board is causing that reading.
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            Comment

              #7
              Re: Acer AL2416W Power supply problem

              ok. so tomorrow i'll buy this solder tip. it can be useful for further cases

              Comment

                #8
                Re: Acer AL2416W Power supply problem

                That is the MOSFET for the power supply PFC Voltage booster circuit, hopefully you did not damage the PFC IC that drive the MOSFET, you will need to look up the spec of the PFC IC and find out if the Gate drive output pin is damaged or not by measuring resistance of the Drive pin and Ground, Drive pin and VCC pin. The PFC Rectifer Diode should also be checked out for short.
                Never stop learning
                Basic LCD TV and Monitor troubleshooting guides.
                http://www.badcaps.net/forum/showthr...956#post305956

                Voltage Regulator (LDO) testing:
                http://www.badcaps.net/forum/showthr...999#post300999

                Inverter testing using old CFL:
                http://www.badcaps.net/forum/showthr...er+testing+cfl

                Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                http://s807.photobucket.com/user/budm/library/

                TV Factory reset codes listing:
                http://www.badcaps.net/forum/showthread.php?t=24809

                Comment

                  #9
                  Re: Acer AL2416W Power supply problem

                  There is also probably a low value resistor in the Drain circuit of the Mosfet,and if the Mosfet has failed by going short circuit, then chances are this resistor has also failed.they are normally very low resistance,something like 0.2Ω to 0.5Ω. and would normally show some evidence of having been damaged.

                  Comment

                    #10
                    Re: Acer AL2416W Power supply problem

                    Originally posted by retiredcaps View Post
                    2) Remove k3568 from the board and retest pins 2-3 out of circuit to see if the readings change.

                    3) Your fuse is bad. "1" on the left hand side of a manual range multimeter means "out of range".

                    4) Retest BD1 pins 1-4 once k3568 is removed. If it still reads 0.8 ohms, remove BD1 and retest pins 1-4 out of circuit.

                    2) ok, removed k3568 and obtained the same "in circuit" values (117-117-0.8)

                    3) i also removed the bad fuse and read "T3.15AH250V P". it can be useful to replace it, right?

                    4) retested all BD1 pins after removing k3568. now i obtained the "out of range" result in all cases, including 1-4.

                    thanks also to budm and rtech now i'm waiting for further instructions (and, possibly, explanation on what happened to the board )

                    Comment

                      #11
                      Re: Acer AL2416W Power supply problem

                      Originally posted by lele.v View Post
                      2) ok, removed k3568 and obtained the same "in circuit" values (117-117-0.8)
                      K3568 is likely bad if pins 2-3 measure 0.8 ohms (shorted) and needs to be replaced.

                      3) i also removed the bad fuse and read "T3.15AH250V P". it can be useful to replace it, right?
                      You will have to replace the bad fuse too.

                      4) retested all BD1 pins after removing k3568. now i obtained the "out of range" result in all cases, including 1-4.
                      Your bridge rectifier is good.

                      thanks also to budm and rtech now i'm waiting for further instructions (and, possibly, explanation on what happened to the board )
                      You will need to clear focused photos of the upper left of the power board for us to identify the PFC circuitry (front and backside).
                      Last edited by retiredcaps; 09-19-2012, 12:38 PM.
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                      Comment

                        #12
                        Re: Acer AL2416W Power supply problem

                        There is a resistor coloured Red Black Silver Gold,close to the Mosefet and easily seen on the photo.that should read 0.2Ω,Suggest you take that out and check the resistance, as the Mosfet has failed.

                        Comment

                          #13
                          Re: Acer AL2416W Power supply problem

                          found the resistor, i read about 0.7/0.8 ohms. you think is failed?

                          i'll search a good camera to take the photos and upload them as soon as possible!

                          Comment

                            #14
                            Re: Acer AL2416W Power supply problem

                            i measured also the resistor on the left of glue (under 1234) and i read 0.7 ohms

                            Comment

                              #15
                              Re: Acer AL2416W Power supply problem

                              Originally posted by lele.v View Post
                              found the resistor, i read about 0.7/0.8 ohms. you think is failed?
                              If you touch your two probes together what do you get?

                              The reading of 0.7 ohms could be correct if your readings above are around 0.5 ohms (i.e. the resistance of your probes).

                              In addition, most resistors fail open circuit.
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                              Comment

                                #16
                                Re: Acer AL2416W Power supply problem

                                Originally posted by retiredcaps View Post
                                If you touch your two probes together what do you get?

                                The reading of 0.7 ohms could be correct if your readings above are around 0.5 ohms (i.e. the resistance of your probes).

                                In addition, most resistors fail open circuit.
                                yes, the resistance of the probes together is 0.5 ohm. so i assume that the resistors' reading of abou 0.7/0.8 are right...

                                so, next thing to do is only posting the photos, right?

                                Comment

                                  #17
                                  Re: Acer AL2416W Power supply problem

                                  Originally posted by lele.v View Post
                                  yes, the resistance of the probes together is 0.5 ohm. so i assume that the resistors' reading of abou 0.7/0.8 are right...
                                  Yes for the red black silver gold resistor.

                                  so, next thing to do is only posting the photos, right?
                                  Photos of the back and front.
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                                  Comment

                                    #18
                                    Re: Acer AL2416W Power supply problem

                                    ok, here are front/back photos of the entire board, front/back of the pfc zone and of the mosfet i removed. i can also provide other detailed photos of other parts of the board if necessary.
                                    Attached Files

                                    Comment

                                      #19
                                      Re: Acer AL2416W Power supply problem

                                      You did not need to remove the heatsink along with the k3568 in order to remove it. You just needed to remove the screw holding the k3568 and then unsolder it's 3 leads.

                                      Also, you never did describe what the original problem was with the monitor.

                                      Comment

                                        #20
                                        Re: Acer AL2416W Power supply problem

                                        Well if you just shorted the Mosfet and the fuse blowing while measuring,the Bridge measures fine,as does the drain resistors,then hopefully just replacing the failed two components will restore operation...lets just hope you have not blown the SMPS chip as well.

                                        Comment

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