LG26LD350 dead

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  • HellasTechn1
    Senior Member
    • Sep 2015
    • 176
    • Greece

    #1

    LG26LD350 dead

    Hello folks how are you all ?

    I have this LG26LD350 that had a blown power supply the psu is the LGP26-10p. In fact i found a blown (cracked) ic500 ice3b0365j , shorted zd501 1n5230 (4.7V 500mw) , and open f501 3.15A.
    I replaced them all but culd not find ice3b0365j so i used an ice 2b365.
    I get no voltages from the psu whatsoever. Ive checked all components appart from the smd's and seem to be ok.
    On the main filter capacitor C607 i get 317V not the 380 i would expect to see. could it be that the ice 2b365 is not working or is not suitable replacement ?
    I dont know where to look next. Any ideas ?
    Thanks !
    Last edited by HellasTechn1; 06-25-2021, 11:42 AM.
  • HellasTechn1
    Senior Member
    • Sep 2015
    • 176
    • Greece

    #2
    Re: LG26LD350 dead

    Anything ?

    Comment

    • dick_barton
      Badcaps Legend
      • Aug 2015
      • 6642
      • Wales

      #3
      Re: LG26LD350 dead

      Ice3B0365J - Vcc 10.6V to 26V, 650V, Rdson 6.35 ohms, 22W @ 230V, 10W @ 85V to 265V, 67Khz

      Ice2B365 - Vcc 8.5v to 21V, 650V, Rdson 0.45 ohms, 67W @ 230V, 45W @ 85V to 265V, 67Khz

      I wouldn't think they are interchangeable due to the power dissipation and series resistance.
      Last edited by dick_barton; 07-05-2021, 09:51 AM.
      Willing to help but I'm no expert.

      Comment

      • dick_barton
        Badcaps Legend
        • Aug 2015
        • 6642
        • Wales

        #4
        Re: LG26LD350 dead

        Having thought about this again, ignore my earlier reply.

        My current thought is that the Rdson is a lot higher for the 3B0365 than for the 2B365 and maybe that's what is causing the issue. Maybe unbalancing the Isense feedback to the IC.
        Willing to help but I'm no expert.

        Comment

        • R_J
          Badcaps Legend
          • Jun 2012
          • 9535
          • Canada

          #5
          Re: LG26LD350 dead

          The ic may or may not work as a replacement, Did you check if the current sense resistor R503, (zd501) is across the resistor.
          What is the VCC voltage on the ic?
          This ic is for the 3.5v standby voltage only.
          Last edited by R_J; 07-06-2021, 06:11 PM.

          Comment

          • HellasTechn1
            Senior Member
            • Sep 2015
            • 176
            • Greece

            #6
            Re: LG26LD350 dead

            Originally posted by R_J
            Did you check if the current sense resistor R503, (zd501) is across the resistor.
            I am not sure what you mean...

            Comment

            • HellasTechn1
              Senior Member
              • Sep 2015
              • 176
              • Greece

              #7
              Re: LG26LD350 dead

              Originally posted by R_J
              The ic may or may not work as a replacement, Did you check if the current sense resistor R503, (zd501) is across the resistor.
              What is the VCC voltage on the ic?
              This ic is for the 3.5v standby voltage only.
              Ok i understad now. The IC is not getting any supply voltage. The current sense resistor reads 1.3Ohms which is normal.
              between the supply pins of the 2b365 (pin 8 GND, pin 7 VCC) there is a Zener diode (ZD502) which is 1n5252 24V zener.

              I think i have just located a potential problem. The zener is a 24V one while the VCC of 2b365 ranges from 8.5 to 21V. Could it be that it is damaged? Tracker image does not suggest a short circuit between the VCC and GND pins of the IC though.

              It is most likely that this issue is irrelevant to the fact that the ic is not getting VCC.

              I have tracked the supply rail back to t501 transformer through D502 and found no fault. Also the transformer windings seem to be ok (continuity tested).

              Comment

              • R_J
                Badcaps Legend
                • Jun 2012
                • 9535
                • Canada

                #8
                Re: LG26LD350 dead

                After a closer the at the ic, the 2B365 will not work, it does not have the vcc startup cell that is in the 3B365.
                The ICE3B365 has an internal startup cell that (internally) takes the drain voltage and produces the vcc startup voltage. This startup cell is missing in the ice2b365 ic.
                Last edited by R_J; 07-08-2021, 09:31 PM.

                Comment

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