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LA-7912P powers on with AC or battery but won't charge.

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    #1

    LA-7912P powers on with AC or battery but won't charge.

    I've got a Packard Bell with a LA-7912P rev 1.0, it runs with the DC adapter plugged in and it will run from the battery if that's plugged in. It only runs on battery if the DC adapter is plugged in. It also won't charge the battery.

    My knowledge is lacking but I have measured ACOK 2.6v and ACDET 1.9v on PU4, I'm hoping i can get some further assistance, thank you.
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    #2
    Re: LA-7912P powers on with AC or battery but won't charge.

    1) is the battery a known good battery?

    2) is the power adapter the original and suitable for this box?

    3) when the unit is booted and with a battery, what does windows report about the battery status?

    4) with the adapter connected, measure and post the voltages with respect to ground on mosfet PQ11.

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      #3
      Re: LA-7912P powers on with AC or battery but won't charge.

      Thanks mon2, yes it's a new battery, the old one was dead, the adapter is good but I'm currently powering with my bench supply so i have an idea of current draw. Not sure about number 3, windows has a password on.
      19v on D, 3.1v on S and D... that doesn't seem right.

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        #4
        Re: LA-7912P powers on with AC or battery but won't charge.

        To turn on PQ11, the GATE of this mosfet should be about 6 volts higher than the SRN (current sense pin) on the charger IC.

        Measure and post the voltage of SRN (pin # 12) of the charger IC.

        For this test, the battery should be attached so that the I2C bus communications can continue to detect the battery.
        Attached Files

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          #5
          Re: LA-7912P powers on with AC or battery but won't charge.

          ACDET 1.9v-Something is wrong.

          Comment

            #6
            Re: LA-7912P powers on with AC or battery but won't charge.

            @mcplslg123, but charger appears to be happy with ACOK @ 2.6v. No? Perhaps could be a bit higher...check the pull up resistor voltage rail.

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              #7
              Re: LA-7912P powers on with AC or battery but won't charge.

              Originally posted by mon2 View Post
              To turn on PQ11, the GATE of this mosfet should be about 6 volts higher than the SRN (current sense pin) on the charger IC.

              Measure and post the voltage of SRN (pin # 12) of the charger IC.

              For this test, the battery should be attached so that the I2C bus communications can continue to detect the battery.
              11.35v

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