Reversed polarity cap killed PSU board

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • mockingbird
    Badcaps Legend
    • Dec 2008
    • 5484
    • -

    #1

    Reversed polarity cap killed PSU board

    I recently recapped an Acer AL2017 LCD. The monitor worked a few hours but then started clicking which I erroneously attributed to a coil. The monitor died completely afterward and there's no power. I opened it up and surely enough, I soldered a Panasonic FC 10V 220uF capacitor the wrong way.

    I'm not sure where to go from here. I replaced it, but there's still no power to the screen. Something is blown. Is there a fuse I should be looking for or is it maybe the starter cap or the main primary?

    Also, the Panasonic cap that was in the wrong way bulged slightly and is probably not good anymore. The other caps look ok. Do you think I should trust them or should I check their ESR?
  • retiredcaps
    Badcaps Legend
    • Apr 2010
    • 9271

    #2
    Re: Reversed polarity cap killed PSU board

    Originally posted by mockingbird
    I'm not sure where to go from here. I replaced it, but there's still no power to the screen.
    If there is no green LED power light, check to see if there is 5V DC on the connector from the power/inverter to the logic board.

    If there is 5V DC present on the connector, test the voltage regulators to see if they are outputting the correct voltages.
    --- begin sig file ---

    If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

    We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

    Please do not post inline and offsite as they slow down the loading of pages.

    --- end sig file ---

    Comment

    • Toasty
      Badcaps Legend
      • Jul 2007
      • 4171

      #3
      Re: Reversed polarity cap killed PSU board

      Photo's of yours top and foil side, please. Model number of board?

      There may be one or 2 fuses depending on the PSU model. They can be the regular cylinder type in ceramic or glass. There is a reddish colored "can style" that is popular, and sometimes a "pico" fuse that can appear as a small resistor or diode. All would -usually- be marked F something on the board.

      No, the bulged cap is shite. In the bin with it. The rest of the caps are probably fine.

      Find the fuse(s) and check it/them with an ohmmeter. The continuity check or lowest scale is perfect.

      Toast
      veritas odium parit

      Comment

      • mockingbird
        Badcaps Legend
        • Dec 2008
        • 5484
        • -

        #4
        Re: Reversed polarity cap killed PSU board

        I will post a picture later hopefully. But I wanted to ask you this... I tested all the picofuses, they all have continuity, but why do they have polarity? It should show continuity regardless.

        If they are defective, should I just bridge it? It will be difficult to replace these little things. I would much rather install a regular fuse somewhere else on the board if I could.
        Last edited by mockingbird; 11-12-2010, 04:22 AM.

        Comment

        • mockingbird
          Badcaps Legend
          • Dec 2008
          • 5484
          • -

          #5
          Re: Reversed polarity cap killed PSU board

          There are main fuses one of which is the black vertical cylindrical one near the plug which is 3.15a 250V. It shows continuity. The next is a glass horizontal fuse in the middle of the board. Also tests OK.

          Here are some pictures someone posted in an different thread, so note that it is not my board, he hadn't recapped it yet. Very high resolution:

          Top Of The Board
          http://www.shadowhunt.com/images/badcaps/VG2021m-1.jpg - Two main fuses. One in the corner right near the power plug. Tests OK, and one in the middle of the board to the right of the four chips. Note: The two blue things to the left and right of the power plug... Either they're MOVs or resistors, forgive my ignorance. They do not show contiunity.

          Bottom Of The Board
          http://www.shadowhunt.com/images/badcaps/VG2021m-2.jpg

          Two more he posted:
          http://www.shadowhunt.com/images/badcaps/VG2021m-3.jpg
          http://www.shadowhunt.com/images/badcaps/VG2021m-4.jpg

          The large green Taicon capacitor to the right is the one I replaced with Panasonic FC but reversed the polarity.

          Thanks for your help.

          Comment

          • Toasty
            Badcaps Legend
            • Jul 2007
            • 4171

            #6
            Re: Reversed polarity cap killed PSU board

            See attached photo of back with info on it.

            Check the fuse, measure the 2 resistors, and use diode check on the dual diode pack. Can be common cathode or anode (see markings on it). Report diode pack numbers please.

            Report findings.

            Toast
            Attached Files
            veritas odium parit

            Comment

            • mockingbird
              Badcaps Legend
              • Dec 2008
              • 5484
              • -

              #7
              Re: Reversed polarity cap killed PSU board

              Fuse F102 tests good. Resistors R107, R108 show 103 Ohms (Don't I have to desolder them to test them?). Dual diode tests OK (I think), shows reading of 004. Markings on it are:

              STPS10H100CFP
              GK09P VW
              CHN 643
              And it has an ST Microelectronics logo on it.

              Comment

              • Th3_uN1Qu3
                Believe in
                • Jul 2010
                • 6031
                • Romania

                #8
                Re: Reversed polarity cap killed PSU board

                Originally posted by mockingbird
                Fuse F102 tests good. Resistors R107, R108 show 103 Ohms (Don't I have to desolder them to test them?). Dual diode tests OK (I think), shows reading of 004.
                That sounds like a short to me. If it reads 004 both ways around then it's definitely shorted.
                Originally posted by PeteS in CA
                Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
                A working TV? How boring!

                Comment

                • mockingbird
                  Badcaps Legend
                  • Dec 2008
                  • 5484
                  • -

                  #9
                  Re: Reversed polarity cap killed PSU board

                  I don't have a diode tester, I'm using Ohms to measure it so a low reading should be ok. The other rectifier also tests the same.

                  edit: I also want to make a correction. I stated in my first post that the cap I reversed was 10V 220uF. I mean to say 10V 2200uF.
                  Last edited by mockingbird; 11-12-2010, 01:28 PM.

                  Comment

                  • mockingbird
                    Badcaps Legend
                    • Dec 2008
                    • 5484
                    • -

                    #10
                    Re: Reversed polarity cap killed PSU board

                    Also, according to the datasheet the middle pin goes to the cathode. I read ~270 for the one you asked me to check and 310 for the one that's also screwed into the heatsink next to it. If I reverse the polarity, it just keeps climbing.

                    Comment

                    • Th3_uN1Qu3
                      Believe in
                      • Jul 2010
                      • 6031
                      • Romania

                      #11
                      Re: Reversed polarity cap killed PSU board

                      In that case the diode is good.
                      Originally posted by PeteS in CA
                      Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
                      A working TV? How boring!

                      Comment

                      • Toasty
                        Badcaps Legend
                        • Jul 2007
                        • 4171

                        #12
                        Re: Reversed polarity cap killed PSU board

                        2 separate circuits. The other is not the one that was "shorted" by the reversed cap.

                        Readings only for the one I asked please - 004 or .004 ?

                        DMM with no diode check? Okay.

                        Try to unsolder just the center leg of the diode pack and measure it. Make sure it is not touching the pad at all. If you can't do that, you'll need to unbolt and unsolder it to measure it. If you get the same readings, then it is shorted and needs to be replaced, and is the culprit. Is there a crack on the surface where it is marked with its' numbers?

                        If this is good, then the problem likely is on the other side of the transformer in the driving circuit.

                        R107 & 108 are good. They are 2 - 200Ω resistors in parallel, so their resistance is 1/2.

                        Toast
                        Last edited by Toasty; 11-12-2010, 04:30 PM.
                        veritas odium parit

                        Comment

                        • mockingbird
                          Badcaps Legend
                          • Dec 2008
                          • 5484
                          • -

                          #13
                          Re: Reversed polarity cap killed PSU board

                          On the lowest Ohm setting, I get 285 today. On two KOhms I get around 1.045. 20 Kohms gets me around 3.13. On 200Kohms, around 13.5. When I set the DMM to "2M" I get the aforementioned .004. I assume these numbers are meaningless, because I read that all a Ohm test on a diode can do is check for continuity in one direction and complete resistance in the other (Which shows it's doing its job).

                          I had to lift the traces to get this thing out (No worries, I'll bridge after). Here are the readings:

                          Speaker setting: 289
                          2K: 1.080
                          20K: 3.34
                          200K: 18.9

                          Reversing polarity shows no continuance. It looks like this diode tests good. Also there are no visible signs of failure on the diode. I am assuming you did not want me to test JUST the middle leg, correct?

                          Comment

                          • Toasty
                            Badcaps Legend
                            • Jul 2007
                            • 4171

                            #14
                            Re: Reversed polarity cap killed PSU board

                            "I had to lift the traces to get this thing out" wtf!?

                            veritas odium parit

                            Comment

                            • mockingbird
                              Badcaps Legend
                              • Dec 2008
                              • 5484
                              • -

                              #15
                              Re: Reversed polarity cap killed PSU board

                              Don't worry, it's nothing. I took the entire thing out and when I was rocking it back and forth, the traces on the underneath came loose. It's difficult for me to pull things out which have more than two legs. It's no problem. Onward. Do you have any other suggestions?

                              Retiredcaps suggested I check the 5VDC output to the logic board. Thankfully it is marked. The third set of pins is +5V. I'm assuming one is positive and one negative. should I check if it is outputting +5v with the board plugged in? Should I measure the 5V from the PSU or from the logic board?

                              Comment

                              • mockingbird
                                Badcaps Legend
                                • Dec 2008
                                • 5484
                                • -

                                #16
                                Re: Reversed polarity cap killed PSU board

                                Does this help? I found this in the service manual:
                                Attached Files

                                Comment

                                • mockingbird
                                  Badcaps Legend
                                  • Dec 2008
                                  • 5484
                                  • -

                                  #17
                                  Re: Reversed polarity cap killed PSU board

                                  Ok, I'm done with this one. Too much time, and I think I caused more damage when I was trying to measure +5V output and touched one of the other pins. Then I DID blow that "W" fuse underneath and now I get no reading.

                                  In the rubbish bin this one goes.

                                  Comment

                                  • Toasty
                                    Badcaps Legend
                                    • Jul 2007
                                    • 4171

                                    #18
                                    Re: Reversed polarity cap killed PSU board

                                    Shame you're not in US, I'd ask you to send it to me.

                                    OTOH: they are going for ~$50 with s/h on Ebay.

                                    Toast
                                    veritas odium parit

                                    Comment

                                    • mockingbird
                                      Badcaps Legend
                                      • Dec 2008
                                      • 5484
                                      • -

                                      #19
                                      Re: Reversed polarity cap killed PSU board

                                      If you pay shipping you can have it. I'd love to see you get it working again, and you can tell me what was wrong. I can ship Canada Post, wouldn't cost you more than $20, possibly a lot less.

                                      Comment

                                      • Toasty
                                        Badcaps Legend
                                        • Jul 2007
                                        • 4171

                                        #20
                                        Re: Reversed polarity cap killed PSU board

                                        Okay. PM sent.
                                        veritas odium parit

                                        Comment

                                        Related Topics

                                        Collapse

                                        • Tynan Dill
                                          Vizio e601i-A3 - Has Sound and Display, But No Backlight - Bad Power Supply Board or Bad LED Bulbs ?
                                          by Tynan Dill
                                          I was given this TV from my great uncle. He said it just wouldn't turn on one day out of nowhere, replaced the TV, and gave it to me to possibly fix and use for myself.

                                          Upon bringing it home and plugging it up, it showed a standby light.

                                          I powered it on and without a flashlight, the display showed the "V" but the lighting is very dim, but visible.

                                          The screen seems to blackout and stay black, but with a flashlight I can see the display.

                                          With my Playstation 4 connected via HDMI, and running a game I can hear sound.

                                          Assuming...
                                          11-22-2024, 01:46 PM
                                        • m1ch43lzm
                                          HP Pavilion 15-eh Board DAG7HAMB8F0 - CPU throttling to 0.4GHz (PROCHOT_EXT) and black screen
                                          by m1ch43lzm
                                          Hi, this is my personal laptop, which the original board (lets call it Board A) blew up PU8700 (TPS51486), making a hole on the board, i had left the laptop at my desk one day with the battery fully charged and didn't touch it for a week, but when i tried to turn it on it didn't
                                          Thought the battery was dead, so i plugged in the charger then tried to power on, the power LED blinked once, charged LED still orange, unplugged the charger, plugged in again and I noticed the "magic smoke" smell, so i unplugged the charger, removed the back cover and saw the blown IC (the "magic...
                                          05-12-2025, 08:37 PM
                                        • Hakuu
                                          LG OLED77G1PUA - No Video / Audio after a TCON Board change and Software Update
                                          by Hakuu
                                          Hi There,

                                          This TV was auto switching off after few seconds with some vertical lines on the screen, so got a new TCON board and replaced it.

                                          After replacing the TCON board it was working fine and i set it up with everything, used for few hours, then had the bright idea to update the software on it. During the update process, TV switched off and now no audio or video. No relay switch sound.

                                          More Details

                                          TV Model - LG OLED77G1PUA

                                          Got the same exact TCON board from TVPartsToday and replaced it. But didnt transfer the EPPROM data (didnt...
                                          07-12-2023, 02:37 PM
                                        • jb_Bak
                                          Sony xbr-65x900c main board issues?
                                          by jb_Bak
                                          Hey guys great forum glad to have found it. I bought a Sony XBR 65X900C cheaply because it didn't work. No signs of life at all not even a light/led. All I hear is a brief high voltage sound when I throw the power to it.

                                          Didn't see any obvious signs of damage so right away started checking voltages. This is what I see:
                                          Power Board Connector that goes to Main board
                                          CN6401
                                          Pin 01 NC
                                          Pin 02 NC
                                          Pin 03 "BL_ON": 0V
                                          Pin 04 "N/C"
                                          Pin 05 "STBY 3.3V": 3.5V
                                          Pin 06 "GND": N/C
                                          Pin 07 "AC_OFF"...
                                          09-27-2021, 04:52 PM
                                        • canadaboy25
                                          Panasonic TC-P54VT25 No image. A or D board?
                                          by canadaboy25
                                          I have a Panasonic TC-P54VT25 that will power on and prime the display but there is no image at all.

                                          The panel is primed as there is a slight glow from the entire panel. This means the problem should be logic related. The service manual also confirms this and recommends replacing the A or the D board.

                                          I have tried to get the TV to display the test sequence but I have been unable to and I don't even know if this TV has a test sequence or not. I tried following tom66's instructions in post #3 on this thread https://www.badcaps.net/forum/showthread.php?t=26790. There was...
                                          01-17-2021, 01:06 AM
                                        • Loading...
                                        • No more items.
                                        Working...