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HP Elitebook 2740p - starts on battery only

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    HP Elitebook 2740p - starts on battery only

    hello! Maybe someone have experience with this issue:

    about year ago laptop got overheated due dusty fan. I replaced it with new one and applied new thermal paste since replacing fan requires disassemble of whole laptop. since then I had every time I turn it on 5 blinks of caps lock + num lock in a row. but, after some series of blinks I was able to continue loading system and I worked completely normal.


    yesterday laptop shut off because power chord slipped. and strange is that laptop didnt went into sleeping mode to preserve battery.


    I tried to turn it on, on power chord, but except 1 blink then pause in total of 5 blinks, I was not able to do anything. display is off. sometimes when I tried in a same way he shuts only after one or two blinks without parked heads of hdd.

    then I tried to remove batt and turn it on only on chord. same thing.

    later, I managed to turn it on, only if on battery only. with blinking code from beginning - 5 times in a row, then pause, then again 5 times...
    if connected to power nothing happening except 1blink x 5times as I said.

    so, laptop starts now only if on battery.

    as I saw blinking codes are:
    1 blink at a time - CPU LEDs blink 1 time CPU not functional
    5 blinks at a time - System board LEDs blink 5 times General system board failure

    here is a link to codes: https://support.hp.com/us-en/document/c01732674


    I am typing on it right now. all looks pretty normal. temperature is normal. cpu 55, mb 51 degrees celsius.


    any idea what can cause problems? thanks.

    #2
    Re: HP Elitebook 2740p - starts on battery only

    Does it post with the battery or you get five blinks ? Dissembled Laptop and you have to come up With some voltage measurements Upload the picture of the mob

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      #3
      Re: HP Elitebook 2740p - starts on battery only

      Yes, I get post with five blinks. Usually I can boot, with battery ofcourse only, after remaining power is drained (holding power button for some time, without batt and chord). Then I return batt, power on, screen is on, blinks starts...

      I cant do anything until five blinks cycles ends. Then I can with esc pressed enter menu and then with selecting "continue with os load", or something like that, continue to windows. No errors in windows. All is running as it should. No bsod or any failure of software.

      thanks

      Comment


        #4
        Re: HP Elitebook 2740p - starts on battery only

        This might seem stupid. But by any stretch of imagination have you maybe enabled battery calibration discharge? It's a setting from windows that will discharge your battery completely so that it can be recalibrated.

        I know this sounds silly.

        But let it die on battery.

        Comment


          #5
          Re: HP Elitebook 2740p - starts on battery only

          So the battery is charging normally but power on only with battery ? What is your MB id

          Comment


            #6
            Re: HP Elitebook 2740p - starts on battery only

            Power adapter cable disconnection caused this. Nothing ran related to battery, nor to any part of system. Nothing was tweaked. Ordinary software only was running.



            Yes, battery is charging completely normal after those first few seconds after boot. If turned off laptop is connected to power adapter then it will blink 1 x 5 times. No display. Fan works very fast. And often just turn off suddenly.

            If unpluged, discharged, then battery reinserted laptop will boot.

            Mainboard Model HP 7007 (0x000000CE - 0x00002178)
            KBC ver 39.36

            HP 600463-001 2740p Motherboard

            Manufacturer Hewlett-Packard
            Model 7007 (CPU 1)
            Chipset Vendor Intel
            Chipset Model Havendale/Clarkdale Host Bridge
            Chipset Revision 12
            Southbridge Vendor Intel
            Southbridge Model QM57
            Southbridge Revision 06
            System Temperature 41 °C


            thanks
            Last edited by selfrepairing; 12-18-2019, 01:32 PM.

            Comment


              #7
              Re: HP Elitebook 2740p - starts on battery only

              Dissembled laptop carefully and check the voltage on pin number 5 Limit_signal voltage DC Jack Connector ,adapter connected to motherboard without battery
              Attached Files

              Comment


                #8
                Re: HP Elitebook 2740p - starts on battery only

                Originally posted by techtiger View Post
                Dissembled laptop carefully and check the voltage on pin number 5 Limit_signal voltage DC Jack Connector ,adapter connected to motherboard without battery
                Easy task, heh, disassembled whole thing. Measured 3.4v

                also,
                Pin 1 shows 0v
                Pin 2 shows 20.2v.

                thank you!

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