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HP 4540s immediately turn off

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    #21
    Re: HP 4540s immediately turn off

    We should have 25 voltage on gate for correct output at the circuit so KBC measure via comparing and allow current pass via signal processing logic.

    Replace cmsrc resistor and remove current limit resistor and check which side is shorted to ground or measure resistance to ground for both pads.

    One other way is measure ACN line resistor ohm and at clr it should be sum of all resistors attached to the line.

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      #22
      Re: HP 4540s immediately turn off

      Resistor PR4004 was replaced. But there is still a problem
      I also removed the resistor PR4001 and checked ohm:
      Red probe on the power input and a problem on the ground OL. Red probe on the ground and black on the 1.5MEGA OHM power supply
      Red probe on the consumer section (DCBATOUT) and black on the ground OL.
      Red probe on the ground and black probe on the consumer (DCBATOUT) vary from 15 megohms down to 4 or 5 megohms

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        #23
        Re: HP 4540s immediately turn off

        It seems all values are good but pu4002 mosfet has 0 volt at gate means charging ic is not functioning and there is no short at pr4001. Have you checked by changing charging ic and also replace pu4002 if you have a spare.

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          #24
          Re: HP 4540s immediately turn off

          tnx
          pu4002 changed but still problem
          The previous charger IC had burned out, so I replaced it.
          I order another IC to be sure.

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            #25
            Re: HP 4540s immediately turn off

            ok
            Last edited by qayyum786; 11-26-2020, 09:27 PM.

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