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replacing schottky diodes on a AV power supply

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    #21
    Re: replacing schottky diodes on a AV power supply

    Originally posted by DjKrish View Post
    SR340 - 5v plus
    SR320 - 12v plus
    B31V present
    this doesn't make any sense. Did you install the other schottky backwards?

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      #22
      Re: replacing schottky diodes on a AV power supply

      maybe the 340's are bad

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        #23
        Re: replacing schottky diodes on a AV power supply

        Originally posted by CapLeaker View Post
        this doesn't make any sense.
        Agreed.

        Either the SB340's were bad ad STJ suggested or connected backwards.
        -OR MAYBE-
        PSU had a hickup by coincidence when the SB340's were installed and somehow voltages were off only then.

        Best way to know is to repeat the experiment. Better yet, test the SB340 diodes outside first - not just with a multimeter, but rather pass 12V DC through one and feed a dummy load. Then reverse the diode and try again. In the reverse direction, the diode should be blocking any current from flowing. If it's partially shorted (i.e. shorted with high resistance), it will pass current in both directions.

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          #24
          Re: replacing schottky diodes on a AV power supply

          Bad or faked SR340?
          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


            #25
            Re: replacing schottky diodes on a AV power supply

            Fake? That i could suspect. The supplier said its a chinese company made. Sighs. Looks like i need to reorder a good quality ones again

            Comment


              #26
              Re: replacing schottky diodes on a AV power supply

              Do you have any broken boards that you can find some similar diodes that you can try?
              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


                #27
                Re: replacing schottky diodes on a AV power supply

                just check any scrap psu's you have for a TO220 package schottky.

                Comment


                  #28
                  Re: replacing schottky diodes on a AV power supply

                  Why not test those SB340 diodes with power? IMO, no need to waste time and money looking for new diodes if you can't confirm the old one(s) is bad.

                  Take a 20V laptop adapter and something with a heating element that has about 10 Ohms resistance and connect it as a load on the laptop adapter through the diode. Then measure to see if the diode has proper voltage drop in the forward direction. After that, reverse the diode and test again. It should block current from going to the heating element. If you can confirm this, then your SB340 diode(s) are not bad and maybe there was another anomaly that happened at the time when you tested the PSU.
                  Last edited by momaka; 09-01-2020, 11:41 AM.

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                    #29
                    Re: replacing schottky diodes on a AV power supply

                    Thanks guys for the inputs. Ive been away for quite a while now. And the parts arrived as well. Fitted in 2 pieces of sr320. Works perfectly. Wonder why the rest didnt work? Hmmmm

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                      #30
                      Re: replacing schottky diodes on a AV power supply

                      Originally posted by DjKrish View Post
                      Wonder why the rest didnt work? Hmmmm
                      Well, if you want to get an answer for that, or at least get a clue, do the test I suggested above with the old rectifiers and the power adapter. If they test bad, then we know. And if they don't, then they weren't the issue and probably something else happened that you didn't realize was happening.

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                        #31
                        Re: replacing schottky diodes on a AV power supply

                        Originally posted by momaka View Post
                        Well, if you want to get an answer for that, or at least get a clue, do the test I suggested above with the old rectifiers and the power adapter. If they test bad, then we know. And if they don't, then they weren't the issue and probably something else happened that you didn't realize was happening.
                        Already tested, its just some cheap Chinese diodes thats not even accurate. Well, the luck was just not there. Ive returned back those diodes and request for originals.

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                          #32
                          Re: replacing schottky diodes on a AV power supply

                          Tested the unit, everything works perfectly fine with the new original diodes.

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