Diode test results show reading both ways

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • AcGeorgiegirl
    Badcaps Veteran
    • Jun 2013
    • 202
    • USA

    #1

    Diode test results show reading both ways

    I've a diode in a tv psb that has a reading forward and bias. This is with it in circuit. Out of circuit, it tested normally. Any thoughts?
  • budm
    Badcaps Legend
    • Feb 2010
    • 40746
    • USA

    #2
    Re: Diode test results show reading both ways

    You need to trace out the connections to see if the diode is connected in parallel with other device or not.
    Pictures of what you are testing?
    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

    • AcGeorgiegirl
      Badcaps Veteran
      • Jun 2013
      • 202
      • USA

      #3
      Re: Diode test results show reading both ways

      Here's a pic of the psb on the tv I am working on. The diode in question is circled. Would it help if I took the same pic of the underside, to show tracings?
      Attached Files

      Comment

      • ReeceyBurger123
        Never Give Up !
        • May 2014
        • 7325
        • Britain

        #4
        Re: Diode test results show reading both ways

        What the fault with the Tv ?
        Please Do Not PM My Page Asking For Help Badcaps Is The Place For Advise, Page Linked For Business Reasons Only. Anyone Doing So Will Be Banned Instantly !

        https://www.facebook.com/Telford-Tel...7894576335359/

        Comment

        • stj
          Great Sage 齊天大聖
          • Dec 2009
          • 30911
          • Albion

          #5
          Re: Diode test results show reading both ways

          CY2 ceramic, lower right corner!

          Comment

          • capwizard
            Badcaps Legend
            • Jun 2016
            • 1991
            • USA

            #6
            Re: Diode test results show reading both ways

            eagle's eyesight ..................
            Attached Files
            Last edited by capwizard; 01-10-2017, 05:13 PM.

            Comment

            • Longbow
              Badcaps Veteran
              • Jun 2011
              • 623
              • USA

              #7
              Re: Diode test results show reading both ways

              Nope, you are looking at some of that grey adhesive, not a ruptured capacitor. Even so, if there were a problem right next to the main primary side rectifier bridge, do you think that it would cause a secondary rectifier to fail or read incorrectly? I think not.

              The fastest way to check the diode is to desolder one leg and re-measure. It is probably a Schottkey and will measure somewhere around .2 volts forward.
              Is it plugged in?

              Comment

              • stj
                Great Sage 齊天大聖
                • Dec 2009
                • 30911
                • Albion

                #8
                Re: Diode test results show reading both ways

                it could cause anything with a 2pin power cord,
                those are the caps coupling the mains to the groundplane!

                Comment

                • budm
                  Badcaps Legend
                  • Feb 2010
                  • 40746
                  • USA

                  #9
                  Re: Diode test results show reading both ways

                  Originally posted by AcGeorgiegirl
                  Here's a pic of the psb on the tv I am working on. The diode in question is circled. Would it help if I took the same pic of the underside, to show tracings?
                  Does it show conduction in both direction if the white connector to the main board is not in place.
                  We do need good clean straight shot of the bottom side of the board too.
                  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

                  • budm
                    Badcaps Legend
                    • Feb 2010
                    • 40746
                    • USA

                    #10
                    Re: Diode test results show reading both ways

                    Originally posted by ReeceyBurger123
                    What the fault with the Tv ?
                    +1
                    History of the TV?
                    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

                    • ReeceyBurger123
                      Never Give Up !
                      • May 2014
                      • 7325
                      • Britain

                      #11
                      Re: Diode test results show reading both ways

                      Originally posted by budm
                      +1
                      History of the TV?
                      We need to be taking a few more baby steps lol
                      Please Do Not PM My Page Asking For Help Badcaps Is The Place For Advise, Page Linked For Business Reasons Only. Anyone Doing So Will Be Banned Instantly !

                      https://www.facebook.com/Telford-Tel...7894576335359/

                      Comment

                      • AcGeorgiegirl
                        Badcaps Veteran
                        • Jun 2013
                        • 202
                        • USA

                        #12
                        Re: Diode test results show reading both ways

                        Originally posted by ReeceyBurger123
                        What the fault with the Tv ?
                        Tv has no standby light or backlight/no image.

                        Comment

                        • budm
                          Badcaps Legend
                          • Feb 2010
                          • 40746
                          • USA

                          #13
                          Re: Diode test results show reading both ways

                          Post #9
                          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

                          • AcGeorgiegirl
                            Badcaps Veteran
                            • Jun 2013
                            • 202
                            • USA

                            #14
                            Re: Diode test results show reading both ways

                            Originally posted by budm
                            Does it show conduction in both direction if the white connector to the main board is not in place.
                            We do need good clean straight shot of the bottom side of the board too.
                            It doesn't show conduction in both directions then. But, it does take a second to get to open OL, after cycling a few numbers around. Here's a pic of the back of the board.
                            Attached Files

                            Comment

                            • AcGeorgiegirl
                              Badcaps Veteran
                              • Jun 2013
                              • 202
                              • USA

                              #15
                              Re: Diode test results show reading both ways

                              Originally posted by ReeceyBurger123
                              We need to be taking a few more baby steps lol
                              The info below is another posting by me at https://www.badcaps.net/forum/showthread.php?t=59414

                              I started this posting because I didn't get a response about the diode issue there, and thought is was important....

                              There's no standby led lighting up. Without the main board connected, I get 5.14 on the 3 pins labeled for 5v for what I assume is standby(con isn't labeled as such...see pics). With main board connected, I get the following pin voltages:

                              1 gnd
                              2 5vcc 5.21
                              3 5vcc 5.21
                              4 gnd
                              5 5vcc 5.21
                              6 13vcc 12.71
                              7 13vcc_AUD 12.71
                              8 gnd
                              9 PWON 3.03
                              10 ACD 3.46
                              11 gnd
                              12 BLON 0
                              13 DIM 0

                              I realize that pins 6 & 7 are supposed to be 13v. I don't know what pins 9 & 10 should be, nor 12 & 13. Also, when checking diodes and fuses, I found that D210A on the Secondary side has reading both ways (208 and 1342) I keep running into this, and am wondering if this is normal on the secondary side, or not? I usually don't take the diodes out of circuit when I test them...maybe this is why I get this?

                              Comment

                              • CapLeaker
                                Leaking Member
                                • Dec 2014
                                • 7967
                                • Canada

                                #16
                                Re: Diode test results show reading both ways

                                In plain English it sez:
                                The PSU has been turned on (pin 9 &10)
                                there backlight's are off (pin 12 &13)

                                So the BLon signal from the main board to the PSU to turn on the backlights is missing. Look at the mainboard and see if the if the BLon voltage is missing there too. If it is, you've got a main board problem.

                                Comment

                                • budm
                                  Badcaps Legend
                                  • Feb 2010
                                  • 40746
                                  • USA

                                  #17
                                  Re: Diode test results show reading both ways

                                  Originally posted by AcGeorgiegirl
                                  It doesn't show conduction in both directions then. But, it does take a second to get to open OL, after cycling a few numbers around. Here's a pic of the back of the board.
                                  OK, let me get this correctly, when testing the diode on board WITH all the connector in place, it shows resistance in BOTH direction, what is the resistance? Ohms, K Ohms?
                                  Same test but WITHOUT other boards connected to the power supply board, resistance is???
                                  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

                                  • AcGeorgiegirl
                                    Badcaps Veteran
                                    • Jun 2013
                                    • 202
                                    • USA

                                    #18
                                    Re: Diode test results show reading both ways

                                    Originally posted by budm
                                    OK, let me get this correctly, when testing the diode on board WITH all the connector in place, it shows resistance in BOTH direction, what is the resistance? Ohms, K Ohms?
                                    Same test but WITHOUT other boards connected to the power supply board, resistance is???
                                    Using diode mode on my DMM, the diode shows 204 and 1331 while the board is connected. Without connection, it shows 204 and OL. I'm sorry, I don't know what you mean by "Ohms, K Ohms"...well, I understand what Ohms are, in general, but not how I'd know numbers other than 204 and 1331. 204 is the forward bias and 1331 the reverse. Are you asking me to test resistance instead of in diode mode?
                                    Last edited by AcGeorgiegirl; 01-11-2017, 03:56 PM. Reason: to add to my answer

                                    Comment

                                    • AcGeorgiegirl
                                      Badcaps Veteran
                                      • Jun 2013
                                      • 202
                                      • USA

                                      #19
                                      Re: Diode test results show reading both ways

                                      Originally posted by CapLeaker
                                      In plain English it sez:
                                      The PSU has been turned on (pin 9 &10)
                                      there backlight's are off (pin 12 &13)

                                      So the BLon signal from the main board to the PSU to turn on the backlights is missing. Look at the mainboard and see if the if the BLon voltage is missing there too. If it is, you've got a main board problem.
                                      Can you show me/tell me where this pin can be found? My board has nothing labeled.
                                      I went ahead and followed the BLon pin wire from psb to main, and tested at the main side. It is still at 0, and so is the DIM pin.
                                      Last edited by AcGeorgiegirl; 01-11-2017, 03:47 PM. Reason: adding something

                                      Comment

                                      • budm
                                        Badcaps Legend
                                        • Feb 2010
                                        • 40746
                                        • USA

                                        #20
                                        Re: Diode test results show reading both ways

                                        Disregard.
                                        Last edited by budm; 01-11-2017, 03:05 PM.
                                        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

                                        Related Topics

                                        Collapse

                                        • SuperAman
                                          PS5 HDMI port diode reading?
                                          by SuperAman
                                          I did an hdmi port repair for a PS5 and I lost the small diode z71 SOD923 on the back of the port. I did a trace repair for pin 19 of the port as well. Without the diode I get no display at all. I tried replacing the diode twice but after I get flux on it the marking comes off so I can't tell if I have it on the right orientation. When I measure I get a reading of 1(open) and 923 in diode mode. Is 923 a normal reading for these and also which side should the reading be with regards to the arrow on the board?...
                                          02-03-2024, 10:16 PM
                                        • abajor
                                          A2141 PP3v3_G3H_RTC_X Diode Reading .104V Voltage 3.39V
                                          by abajor
                                          Have an A2141 which is reading about 5.2V 0.07A on all USB jacks, started doing the measurements.

                                          PPBUS_3GH diode: measures good .45V
                                          PPBUS_3GH Voltage: maybe not so good 12.25V maybe bad T2? Unit did not come up in DFU on configurator.

                                          The weird so far is
                                          PP3v3_G3H_RTC_X diode: .104V (WTF?)
                                          PP3v3_G3H_RTC_X voltage: 3.39V (Normal)

                                          Stopped there attempted reverse voltage injection at PP3v3_G3H_RTC_X with 1V. Instead of the circuit sinking any current, My PSU suddenly reads 3.4V with no current draw.
                                          Not sure what any of this means...
                                          03-18-2025, 10:27 PM
                                        • iMuhtaseb
                                          A2681 Keyboard, trackpad and sleep?!
                                          by iMuhtaseb
                                          Wow it's been a while since I posted!

                                          This is a weird case, it has a history of liquid spill a year ago but customer did not want to replace neither trackpad or keyboard.. fast forward for today:

                                          A2681 turns on but not trackpad or keyboard feedback (or external keyboard and mouse) and then after a minute or so the Mac sleeps..

                                          It's a NOT a sleep sensor or trackpad or keyboard or daughterboard or anything else (I replaced all those); it's the logic board..

                                          Tested another locked logic board on customer's top case and it posted with keyboard and...
                                          05-22-2025, 09:59 AM
                                        • ca-gamer
                                          MSI GTX 1070Ti problem with PCIE?
                                          by ca-gamer
                                          Hi All,

                                          I have a problem with my 1070Ti.

                                          9/10 times card fails to post in PCIE x16 socket. When it finally posts it shows random PCIE reading in GPU-Z. Rarely it shows x16, most of the times it will be either x4 or x1, sometimes x8. But still it will crash with BSOD in x16 slot sometimes even after 1 minute and sometimes it will happen after an hour.

                                          Moving card to x4 PCIE slot improves it. It will post most of the time (I would say 8/10 times) and I can even play games for hours at full speed (I haven't spotted and slow downs in FPS vs x16). However randomly...
                                          10-27-2024, 11:11 PM
                                        • karoliens
                                          820-01700 PPVCC_S0_CPU normal resistance to ground/diode reading?
                                          by karoliens
                                          I am working on this board that has some water damage though not around this rail but I measured it anyway to rule out that CPU is not fried.
                                          Resistance to ground on PPVCC_S0_CPU rail is 2Ohm and in diode mode it shows 0V.
                                          What is the normal reading on that rail?
                                          TIA
                                          09-11-2022, 12:55 PM
                                        • Loading...
                                        • No more items.
                                        Working...