Vizio M502i-B1 Power Supply Issue

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  • JunkmanJimbo
    Senior Member
    • Mar 2017
    • 194
    • United States
    #1

    Vizio M502i-B1 Power Supply Issue

    Hey guys, I have a problem with this tv that is strange to me. The power supply has standby voltage, but when the power cord is disconnected and reconnected, the tv doesn't want to power up unless I disconnect the connector at the power supply that leads to the main board and reconnect it. Then the tv seems to work. I have tried multiple main boards and the same thing happens, so I know the main board is good.
    My question is....can someone tell me which component or components can cause this on the power supply? I would like to repair the power supply if possible but I'm not sure where to start. I'm not very good at board level testing. Thanks in advance for anyone that can help.
    Tags: None
    • CapLeaker
      Leaking Member
      • Dec 2014
      • 8188
      • Canada
      #2
      Re: Vizio M502i-B1 Power Supply Issue

      in that weird state, where the TV should be on, measure the DCV on the PSon and on/off and dim pins on the PSU. Better yet check all the pins and post the pin name and the voltage measured with the tv off, then on.

        Comment

        • R_J
          Badcaps Legend
          • Jun 2012
          • 9551
          • Canada
          #3
          Re: Vizio M502i-B1 Power Supply Issue

          I would replace the small electrolytic caps, C9805, C9308 and C9112 and maybe also C9305. These are on the primary ic's (pfc etc.) vcc lines and if they are weak, the power supply may not operate properly.

            Comment

            • JunkmanJimbo
              Senior Member
              • Mar 2017
              • 194
              • United States
              #4
              Re: Vizio M502i-B1 Power Supply Issue

              Capleaker, here is my voltages. I hope you can read them ok.
              Attached Files

                Comment

                • JunkmanJimbo
                  Senior Member
                  • Mar 2017
                  • 194
                  • United States
                  #5
                  Re: Vizio M502i-B1 Power Supply Issue

                  R_J, thanks for the suggestion. I didn't see a C9112 but I got some caps ordered. They should be here Sunday so I will give an update Sunday night or Monday.

                    Comment

                    • CapLeaker
                      Leaking Member
                      • Dec 2014
                      • 8188
                      • Canada
                      #6
                      Re: Vizio M502i-B1 Power Supply Issue

                      I think you didn't measure all pins on CN9101. It has 16 pins.what is the pin name on the 3.3V rail (the very first on top of the list)? 3.3V only measures 1.1V when the TV won't turn on.
                      Last edited by CapLeaker; 03-19-2020, 02:52 PM.

                        Comment

                        • R_J
                          Badcaps Legend
                          • Jun 2012
                          • 9551
                          • Canada
                          #7
                          Re: Vizio M502i-B1 Power Supply Issue

                          Originally posted by JunkmanJimbo
                          R_J, thanks for the suggestion. I didn't see a C9112 but I got some caps ordered. They should be here Sunday so I will give an update Sunday night or Monday.
                          I made a typo. I ment C9122 (next to ic9101)
                          Last edited by R_J; 03-19-2020, 03:38 PM.

                            Comment

                            • JunkmanJimbo
                              Senior Member
                              • Mar 2017
                              • 194
                              • United States
                              #8
                              Re: Vizio M502i-B1 Power Supply Issue

                              CapLeaker, the 1.1v reading appears to be on the on/off pin. And the 3.3v appears to be the dim pin.

                                Comment

                                • JunkmanJimbo
                                  Senior Member
                                  • Mar 2017
                                  • 194
                                  • United States
                                  #9
                                  Re: Vizio M502i-B1 Power Supply Issue

                                  Thanks R_J.

                                    Comment

                                    • CapLeaker
                                      Leaking Member
                                      • Dec 2014
                                      • 8188
                                      • Canada
                                      #10
                                      Re: Vizio M502i-B1 Power Supply Issue

                                      So when that tv is in that weird state as you say, are the backlights on or off? 1.1v isn’t enough to turn them on. Next, the same on / off pin is on the other connector where the backlights plug in.

                                        Comment

                                        • JunkmanJimbo
                                          Senior Member
                                          • Mar 2017
                                          • 194
                                          • United States
                                          #11
                                          Re: Vizio M502i-B1 Power Supply Issue

                                          No backlights are on. The TV does show the standby light for a few seconds and then it's dead.

                                            Comment

                                            • nomoresonys
                                              Badcaps Legend
                                              • Jan 2013
                                              • 12206
                                              • U.S.
                                              #12
                                              Re: Vizio M502i-B1 Power Supply Issue

                                              Check D9102, tv unplugged from power, diode mode should read 2xx ~7xx or so in one direction and OL or 1 when you reverse the meter probes.
                                              Last edited by nomoresonys; 03-20-2020, 10:16 AM.
                                              Quit because THIS SITE LETS A ROGUE MEMBER TYPE ANY GARBAGE HE PLEASES AND THE POWERS THAT BE NEVER DO ANYTHING ABOUT IT SO HE NEVER QUITS. THEN YOU GET A PENALTY FOR RESPONDING TO HIS ATTACKS. BEEN GOING ON FOR WAY TOO LONG. DONE SUPPORTING A SITE THAT ALLOWS THIS BS.

                                                Comment

                                                • JunkmanJimbo
                                                  Senior Member
                                                  • Mar 2017
                                                  • 194
                                                  • United States
                                                  #13
                                                  Re: Vizio M502i-B1 Power Supply Issue

                                                  Thanks nomoresonys. It checks good at .510.

                                                    Comment

                                                    • nomoresonys
                                                      Badcaps Legend
                                                      • Jan 2013
                                                      • 12206
                                                      • U.S.
                                                      #14
                                                      Re: Vizio M502i-B1 Power Supply Issue

                                                      Simple test, with tv unplugged from power, unhook cable from powerboard to mainboard, leave it out, plug power cord into powerboard, do you have steady 5 volt on the standby pin.
                                                      Quit because THIS SITE LETS A ROGUE MEMBER TYPE ANY GARBAGE HE PLEASES AND THE POWERS THAT BE NEVER DO ANYTHING ABOUT IT SO HE NEVER QUITS. THEN YOU GET A PENALTY FOR RESPONDING TO HIS ATTACKS. BEEN GOING ON FOR WAY TOO LONG. DONE SUPPORTING A SITE THAT ALLOWS THIS BS.

                                                        Comment

                                                        • JunkmanJimbo
                                                          Senior Member
                                                          • Mar 2017
                                                          • 194
                                                          • United States
                                                          #15
                                                          Re: Vizio M502i-B1 Power Supply Issue

                                                          Yes I do. 5.13 volts

                                                            Comment

                                                            • CapLeaker
                                                              Leaking Member
                                                              • Dec 2014
                                                              • 8188
                                                              • Canada
                                                              #16
                                                              Re: Vizio M502i-B1 Power Supply Issue

                                                              PSon and BLon does come from the main board. Can you remove the BLon pin from the plug, take a 1k resistor and jump VSB to BLon and see if TV behaves normally. You don't want to back feed power to the main board.

                                                                Comment

                                                                • JunkmanJimbo
                                                                  Senior Member
                                                                  • Mar 2017
                                                                  • 194
                                                                  • United States
                                                                  #17
                                                                  Re: Vizio M502i-B1 Power Supply Issue

                                                                  CapLeaker, I have tried about 4 different mainboards and the TV acts the same on all 4. Also, I don't have the knowledge to do what you're suggesting. I also don't have a 1k resistor. If I actually knew how to do this, what would it tell me?

                                                                    Comment

                                                                    • nomoresonys
                                                                      Badcaps Legend
                                                                      • Jan 2013
                                                                      • 12206
                                                                      • U.S.
                                                                      #18
                                                                      Re: Vizio M502i-B1 Power Supply Issue

                                                                      Try this, with everything hooked up, test the PS_ON pin, read it with tv plugged in but power off, which is standby then hit power and see if it changes, note the voltage of both conditions, do the same thing with ON/OFF pin, we're trying to see if you have the correct voltage and if it's changing like it should. The 1.1 volts you describe is what does not add up as CapLeaker said.
                                                                      Last edited by nomoresonys; 03-20-2020, 01:27 PM.
                                                                      Quit because THIS SITE LETS A ROGUE MEMBER TYPE ANY GARBAGE HE PLEASES AND THE POWERS THAT BE NEVER DO ANYTHING ABOUT IT SO HE NEVER QUITS. THEN YOU GET A PENALTY FOR RESPONDING TO HIS ATTACKS. BEEN GOING ON FOR WAY TOO LONG. DONE SUPPORTING A SITE THAT ALLOWS THIS BS.

                                                                        Comment

                                                                        • nomoresonys
                                                                          Badcaps Legend
                                                                          • Jan 2013
                                                                          • 12206
                                                                          • U.S.
                                                                          #19
                                                                          Re: Vizio M502i-B1 Power Supply Issue

                                                                          Maybe also check the bottom of your powerboard for bad/cold/loose/cracked solder joints, look closely sometimes they look good but are not. look at joints of components on heatsinks and transformer joints, they take the most abuse.
                                                                          Quit because THIS SITE LETS A ROGUE MEMBER TYPE ANY GARBAGE HE PLEASES AND THE POWERS THAT BE NEVER DO ANYTHING ABOUT IT SO HE NEVER QUITS. THEN YOU GET A PENALTY FOR RESPONDING TO HIS ATTACKS. BEEN GOING ON FOR WAY TOO LONG. DONE SUPPORTING A SITE THAT ALLOWS THIS BS.

                                                                            Comment

                                                                            • JunkmanJimbo
                                                                              Senior Member
                                                                              • Mar 2017
                                                                              • 194
                                                                              • United States
                                                                              #20
                                                                              Re: Vizio M502i-B1 Power Supply Issue

                                                                              Everything hooked up, plugged in, power off....on/off-3.24v, ps_on-1.14v
                                                                              Hit power but nothing happen and voltages stayed the same.
                                                                              I unplugged the connector from the mainboard and plugged it back in and then I had 0v on on/off and .10v on ps_on.
                                                                              I hit the power button and then I had 3.24v on on/off and .06v on ps_on.
                                                                              The tv powered on after about 20 to 30 seconds and then I had 3.13v on on/off and 3.20v on ps_on.

                                                                                Comment

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