elitebook 840 G1 - dead, need help

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hello all,

need help for an elitebook 840 G1, MB : 6050A2560201
The laptop worked perfectly untill the message "hardware failure" appear on the screen
sins, it is dead : no charging led, no power, no fan spin
already try to do reset bios and discharge caps, the same

measures :
main power rail : 19V
L6100 : 3.3V
L6150 :5V
Power btn : 3.3V except LED_PWRSTBY 2.6 on off course button led is not comming on
L6300 : 1.05V
L6000 : 1.03V
L6200 : 0V
L6600 : 0V

on the other side :
Q6050 1V on drain, 0,654 on source
Q6051 : 0,654 and 0,937
Q6012 have 19v on drain and gate, and never drop gate when pwr button pushed

i have verified that power button does on/off goes to 0V from 3.3V

so i think this couls be SIO, but something strange, if i plug the charger partialy, the power button led comes but blink all the time , and it shut down when the charger is plugged completely

if i measure the lines in this setup, all lines are egal except on Q6051 the voltage is oscillating between 0,654 and less

no short find on any coil or caps
nothing went hot when plug in, just cpu very little warm

what can i check now ?

thanx

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Re: elitebook 840 G1 - dead, need help

hello
some other informations
all the tries were made without battery
so i try with :
with battery , l6000 rise to 12V, and so the mosfet too
but all this area is really hot! and power button not blink with charger partialy plugin.

[mcplslg123]

Re: elitebook 840 G1 - dead, need help

Seems like something wrong in dc in or charger area. Check U6000 Pins for voltages and make sure Q6000/Q6001 mosfets are not shorted.

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Re: elitebook 840 G1 - dead, need help

Hello
thanx for help
voltages on u6000 seems to be ok
i measure diode and resitance for the two mosfets
Q6000 seems ok
Q6001 seems strange :
in diode mode i have 0,135 red probe on source, black on drain, 2.99 if i red probe on drain
in Ohm mode : 155 ohm red probe on source, and very instable measure red probe on drain, oscillating between 6 and 20kohm never stable

other weird things :
xx if i touch u6100 with my finger, i heard a bzzzz sound and then the 3.3 and 5V shut down. all measure are ok near this chip
xx the u6600 have no voltages except 3 and 5V, but if i understand it is a chip for control of cpu , so if the laptop not start it is normal, right ?

thanx guys

[KvnTM]

Re: elitebook 840 G1 - dead, need help

xx if i touch u6100 with my finger, i heard a bzzzz sound and then the 3.3 and 5V shut down. all measure are ok near this chip

Remember that you skin is conductive. Touching it is most likely messing with the feedback circuit and the buck converter is shutting off.

xx the u6600 have no voltages except 3 and 5V, but if i understand it is a chip for control of cpu , so if the laptop not start it is normal, right ?

If you mean the buck converter for cpu vcore that is completely normal. There will be no vcore if the board is off.

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Re: elitebook 840 G1 - dead, need help

ok thank you
as the voltages are ok (3.3 and 5V for one, and OV shut off for the other) this part is ok
great

i think the variation of resistance on mosfet Q6001 and the fact that is the area which is hot, there is probably a problem on this line ? the value of resistance is normal ?

thanx

[KvnTM]

Re: elitebook 840 G1 - dead, need help

ok thank you
as the voltages are ok (3.3 and 5V for one, and OV shut off for the other) this part is ok
great

i think the variation of resistance on mosfet Q6001 and the fact that is the area which is hot, there is probably a problem on this line ? the value of resistance is normal ?

thanx

Desolder Q6001 and measure the resistances:
Gate to Source should be a high resistance.
Drain to Source should be in the MOhm range.

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Re: elitebook 840 G1 - dead, need help

hello
some news : desolder Q6001 , looks fine, not short
i have alxays the same issue, no led no fan no power nothing but 10V 3.3V 5V 1.05V ok
i have extract EC.bin from winbond chip, seems ok compare to one given in the specific tread
but bios chip can't be extract ,right ?

can my problem could due to bios ?

[mcplslg123]

Re: elitebook 840 G1 - dead, need help

If any paricular part of the mobo is heating up, its not likely bios issue-so leave that untouched and rather find out what is shorted.

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Re: elitebook 840 G1 - dead, need help

Ok. Copy that.
But what i find strange IS that this part cet warm only if batterie IS plug in.
And although thé voltage : it slowly rise from 11v to 12.5v

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Re: elitebook 840 G1 - dead, need help

hello
some news
i decided to give up, nothing find short or something
after assembled the entire laptop, i decided to try another time to power it on
i pressed the power button, and LED turn on !!! but for only 4 seconds, then caps lock led turn on once and the laptop shut down.
nothing since
it's the first time it shows me a little bit of life

what could it be then ?
i understand nothing on this one

thx all

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Re: elitebook 840 G1 - dead, need help

and more news;
try to put lab power supply directly on battery port (of course without 3V rail)
when i push power button i have the charging led that shines 9 times
but not start at all

i read that there's a one wire circuit on this board, which voltage should i have on middle pin of charger ? mine got 19V

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Re: elitebook 840 G1 - dead, need help

hello, some other news, more interesting i think
i've left the laptop for 24H without battery or anything
i have charged the battery with power supply
now the laptop gives me a error code i think, when i plug the charger or when i put the charged battery, the leds flash like this :

charging led : orange-white-orange-white-orange-white-orange-off in cycle
and at the same time with the last orange one i have : power led, caps lock ledand a white led near charging led that came on ONE time and then shut.

this loop untill i remove charger or battery.

this one could help you ?
thank you for your hellp