HP EliteBook 8460p doesn't turn on

[new_1]

https://youtu.be/0MkBwakDwlk


i've included link for video showing the issue
the laptop doesn't start and only numlock light once and off or sometimes it stayed lighting for two second and off. there's no response from the laptop
it started two days ago the lap work fine then restart from it's own few times
then when i try to start it show the logo screen then restart and now won't start and doing that symptoms

what i've tried.
changes thermal paste, Bios battery, Ram , even the processor , power Adapter

so what could be the issue?

[mon2]

There may be a shorted component on the board.

Start with, removing all power. Meter in resistance mode.

Measure the resistance to ground of +VBATR. This is the main power rail. Checking if the main power rail is shorted. Post the measurement.

Confirm that you are using a 90W or higher rated power adapter for this unit.

Next, attach the power adapter. Measure the voltage to ground on each pin of mosfet @ Q29.

Source (1-2-3) ; select any of these pins in the group
gate (4) ; must be ~25v to enable this mosfet to power the main power rail
Drain (5-6-7-8) ; select any of these pins in the group

Post the measurements.

[new_1]

first of all I would like to thank you very much for helping me. I really appreciate it

1) Measure the resistance to ground of +VBATR.
it's not shorted measurements are in Mega Ohm

2) Confirm that you are using a 90W or higher rated power adapter for this unit.
unfortunately i have only two original adapter of the laptop which are 65W and I'll use them to double check measurements.. till i can get 90W power adapter

3) Source (1-2-3) : 19.55 v
gate (4) : 25.49 v
Drain (5-6-7-8) : 19.55 v

awaiting for your instructions
and thanks again for any help your giving me

[mon2]

The gate voltage (pin #4) is boosted and this is forcing this N-channel mosfet to enable properly. The main power rail is being powered under the netname of +VBATR.

Confirm again the voltage to ground of your RTC BIOS battery. We repaired 3 units in the past 2 weeks that were each linked to a drained RTC battery.

Otherwise...

Remove all power. Meter in resistance mode.

Suggest to measure the resistance to ground of each inductor on the board (usually are grey in color and will be with 2 leads). This is to check if any of the power rails are with a lower resistance than normal and then the power regulator will sense this excessive current draw and power down. When a rail shuts off, so does the board.

A low voltage power rail will be with a low resistance, by design. Post all details of any suspects. When you search for 'VBATR' in the schematics, you will see that this high voltage will mate with the high side of a mosfet. That is, there will be a high side and a low side mosfet (goes to ground) which work as a pair to dial down the high ~19v to a safe value for the specific rail. For example, 3v3 or 5v0, etc.

Start with confirming the resistance to ground of the ALWAYS ON rails = U5006. Confirm the voltages of +V3AL and +V5AL.

[new_1]

mon2 thanks for you help

1)Confirm again the voltage to ground of your RTC BIOS battery
3.19 V

2) measure the resistance to ground of each inductor on the board
12.03 ohm, 12.0 ohm, 12.03 ohm, 25.03 ohm , 88 kohm



620 ohm, 105 ohm, 63.55 ohm, 9 ohm , 37.5 ohm


3) A low voltage power rail will be with a low resistance, by design. Post all details of any suspects. When you search for 'VBATR' in the schematics, you will see that this high voltage will mate with the high side of a mosfet. That is, there will be a high side and a low side mosfet (goes to ground) which work as a pair to dial down the high ~19v to a safe value for the specific rail. For example, 3v3 or 5v0, etc.

i understand this part many thanks

4) Start with confirming the resistance to ground of the ALWAYS ON rails = U5006. Confirm the voltages of +V3AL and +V5AL.
i'm not sure exactly which pin of U5006 that you want me to measure it's resistance to ground but i assume it's the one connected to +V5AL which is pin 17 according to the schematics and it's resistance is in mega ohm 5.9 mega ohm

As for +V3AL i measure it on U13 and it's 2.2 mega ohm

i hope i got you right about this Start with confirming the resistance to ground of the ALWAYS ON rails = U5006. Confirm the voltages of +V3AL and +V5AL.

kindly if there's any correction let me know
thanks for your help it's very appreciated

[mon2]

Is the power adapter from HP or another brand? HP uses an analog signal to announce the power rating of the adapter. This detection is important to allow for the board to boot properly. Without this signal, the adapter may appear to be under rated.

From some internet searches, 65W is reported to be ok for this model.

What are the voltages to ground for:

+V3AL
+V5AL

For the inductor measurements - post their locations from the schematics. Unable to zoom in on their values in the posted pics.

[new_1]

mon2 thanks for your reply

1)Is the power adapter from HP or another brand?
it's original HP adapter

https://ibb.co/kgpBdMYs



2) What are the voltages to ground for:

+V3AL : 3.35 V
+V5AL : 5.41 V


3) For the inductor measurements - post their locations from the schematics. Unable to zoom in on their values in the posted pics.
i post links where you can open and zoom the pictures
the link for the first picture
https://ibb.co/fd4dP8gD


the link for the second picture
https://ibb.co/RGtd0mJn

[mon2]

What are the white silk screen markings of this region of the board? Unable to read the values in the posted pics.

[new_1]

mon2 thanks for your reply

if you like i can send you the motherboard BoardViewe file , it shows all the component numbers and places. if it will help you



https://ibb.co/gbV64v0



https://ibb.co/jkgQJ5LC

[mon2]

Yes, please post it here:

https://www.badcaps.net/forum/docume...ptop-schematic

L3 is ok since this is the 1v05 rail. That is, low voltage rails, by design will have a low resistance to ground. This rail is ok.

[new_1]

hello mon2 thanks for your reply

i tried to upload the file there but says i'm not allowed to upload F2B files anyway the file name is INVENTEC_CLASH_6050A2398701-MB-A02_-_boardview.F2B

actually L3 is 12.03 ohm resistance
but L3051 is the lowest one with 9 ohm resistance

so what would be the next step.

awaiting for your help

[mon2]

L3051 is also ok since this is the GPU power rail. Some GPUs can be as low as 0R5 ohms and still be ok. No issue here.

Did this HP charger work for you on this logic board in the past?

Measure the voltage to ground of ADP_PRES @ U6-A pin # 1.

The schematic references a 90W unit.

[new_1]

mon2 thanks for your reply

1) L3051 is also ok since this is the GPU power rail. Some GPUs can be as low as 0R5 ohms and still be ok. No issue here.
thanks for explanation .

2) Did this HP charger work for you on this logic board in the past?
yes of cource actually the lap was working fine 3 or 4 days ago before that happen. and it's not only 1 power adapter but i have 2 power adapter which working fine.

3) Measure the voltage to ground of ADP_PRES @ U6-A pin # 1.
3.3 V - 3.27 V

4) The schematic references a 90W unit.
it's the motherboard model 6050A2398701-MB-A02

[new_1]

mon2 do you think there's a hope for it to get fixed or it's done forever?