Hello all,
I have at least three notebooks with a very similar issue, and I do not know how to solve them, or at least diagnostically how to narrow down the error. I kindly like to ask you to help me with the HP Probook 440 G6 I have (DAX8JMB16E0 REV:E) now. I cant find any schematics or boardviews, they are available on paid sites only.
Symptoms are: The notebook powers on, power and charging light lights up, there is fan spin, keyboard backlight works, CPU heats up, but no screen backlight, and no POST. I get 5 blinking error codes, though I am not sure about this as the notebook is also constantly power cycling, it is possible that the cycling is cutting the error code sequence short.
At first I thought this is a clear-cut BIOS issue, so I reflashed the BIOS with a cleaned version, hoaca was kind enough to provide me with one. This did not help, so I started measuring, please see the attached photo showing resistance-to-ground for all coils as well as voltages present. I think that the resistances are all normal, and every coil has a normal voltage, except one, near the VCORE coils, which has 0V.
Then I started measuring MOSFET's, and I found one EMB20N03V at the bottom (circled green on the photo), which seemed a little bit burnt, and the Source to Gate resistance was only 1 Ohm. So I replaced it with a new one, after which the Source to Gate resistance was somewhere around 3-4KOhm. Then I powered on the notebook, but it still did not work, and now the Source to Gate resistance of the new MOSFET was again 1 Ohm.
Something is killing this MOSFET again and again, or so I assumed, because the interesting thing is that after a couple of hours (or maybe a day) the source to gate resistance of the MOSFET "resets" to around 3-4k.
I do not know where to go from here, and as I said earlier, I have multiple notebooks with the same fault. I would really appreciate it if somebody could pont me in the right direction.
Thank you all very much in advance!
Cheers,
sect-sin
I have at least three notebooks with a very similar issue, and I do not know how to solve them, or at least diagnostically how to narrow down the error. I kindly like to ask you to help me with the HP Probook 440 G6 I have (DAX8JMB16E0 REV:E) now. I cant find any schematics or boardviews, they are available on paid sites only.
Symptoms are: The notebook powers on, power and charging light lights up, there is fan spin, keyboard backlight works, CPU heats up, but no screen backlight, and no POST. I get 5 blinking error codes, though I am not sure about this as the notebook is also constantly power cycling, it is possible that the cycling is cutting the error code sequence short.
At first I thought this is a clear-cut BIOS issue, so I reflashed the BIOS with a cleaned version, hoaca was kind enough to provide me with one. This did not help, so I started measuring, please see the attached photo showing resistance-to-ground for all coils as well as voltages present. I think that the resistances are all normal, and every coil has a normal voltage, except one, near the VCORE coils, which has 0V.
Then I started measuring MOSFET's, and I found one EMB20N03V at the bottom (circled green on the photo), which seemed a little bit burnt, and the Source to Gate resistance was only 1 Ohm. So I replaced it with a new one, after which the Source to Gate resistance was somewhere around 3-4KOhm. Then I powered on the notebook, but it still did not work, and now the Source to Gate resistance of the new MOSFET was again 1 Ohm.
Something is killing this MOSFET again and again, or so I assumed, because the interesting thing is that after a couple of hours (or maybe a day) the source to gate resistance of the MOSFET "resets" to around 3-4k.
I do not know where to go from here, and as I said earlier, I have multiple notebooks with the same fault. I would really appreciate it if somebody could pont me in the right direction.
Thank you all very much in advance!
Cheers,
sect-sin
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