HP 250 G8 (2X7L0EA) dead

[m.tech]

Hello everyone,
this is my first post on the forum, I hope I don't make any mistakes, I apologize in advance.
I am writing to ask for help about a pc of mine, HP 250 G8 (2X7L0EA).
The computer months ago, did not turn on. I tried several keystrokes, and it gave no signs, suddenly then it turned on and worked smoothly.
Now again it won't turn on, I tried Win+V and Win+B keystroke comminution, it won't log on. No screen.
I created a bios reset pendriver with hp software, but it won't boot.
I opened the notebook case.
When I press the boot key, the fan starts for about 3 seconds and a biacno led lights up, the display remains black. After these 3 seconds everything goes dead again.
Can you please help me? Thank you all in advance.
Marco

[m.tech]

Could it be a bios problem?

[m.tech]

The fan no longer turns on. Only a white LED for a few seconds and then everything turns off.
I installed a new motherboard. The PC started, worked for a few minutes, and began to install some updates. Suddenly the monitor turned off and did not respond to any commands.
After several minutes I turned off the PC from the power button. I tried to turn it on, it did not turn on anymore. Same problem as the first motherboard.
The LED lights up for a few seconds and then turns off.
Can someone help me please?
Could it be a corrupted bios update on the hard disk?
Help me please. Thanks
PS sorry, I use the translator, if something is not clear, I can repeat.

[mon2]

To confirm, the bios update never did proceed since the laptop failed to boot? Correct? For now, we do not know if it is the bios so leave the bios alone for now.

Often, the faults are in the power path from the power adapter to the logic board. Be sure your power supply is the original. No liquid spills?

Would you have a multimeter for testing?

The schematic for your logic board is available and is the last post here:

https://www.badcaps.net/forum/troubl...board-scematic

From this schematic, need to review the power path and also review the charger circuit sticky by piernov - see above.

Remove all power. Meter in resistance mode.

Measure the resistance across the DCin mosfets @ PQB11 and PQB12. Often, the faults are between these 2 parts.

These mosfets have source pins 1-2-3 shorted; pin 4 = gate pin; 5-6-7-8 = drain pin cluster.

Use the meter (with no power / no battery to the board) to check each mosfet.

Test source

(1-2-3) & drain (5-6-7-8) ; select one pin from each group
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement. Repeat for the 2nd dcin mosfet. Each measurement should be hundreds of k ohms or higher. If not, the part may be shorted and needs to be replaced.

Would you have access to hot air tools + soldering tools + flux + tweezers? If not, after the diagnostics, will have to work with a local phone repair shop that is able to perform low level component repairs.

[mon2]

To confirm, the bios update never did proceed since the laptop failed to boot? For now, we do not know if it is the bios so leave the bios alone for now.

Often, the faults are in the power path from the power adapter to the logic board. Be sure your power supply is the original. No liquid spills?

Would you have a multimeter for testing?

The schematic for your logic board is available and is the last post here:

https://www.badcaps.net/forum/troubl...board-scematic

From this schematic, need to review the power path and also review the charger circuit sticky by piernov - see above.

Remove all power. Meter in resistance mode.

Measure the resistance across the DCin mosfets @ PQB11 and PQB12. Often, the faults are between these 2 parts.

These mosfets have source pins 1-2-3 shorted; pin 4 = gate pin; 5-6-7-8 = drain pin cluster.

Use the meter (with no power / no battery to the board) to check each mosfet.

Test source

(1-2-3) & drain (5-6-7-8) ; select one pin from each group
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement. Repeat for the 2nd dcin mosfet. Each measurement should be hundreds of k ohms or higher. If not, the part may be shorted and needs to be replaced.

Need hot air tools + soldering tools + flux + tweezers. If not available, after the diagnostics, will have to work with a local phone repair shop that is able to perform low level component repairs.

[mon2]

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[m.tech]

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Hi, thanks for your reply.
I use the original power supply, and I have a multimeter to test.
can you tell me the full link?

[mon2]

Here is where you can download the full schematic & boardview file to hunt down the referenced mosfets:

https://www.badcaps.net/forum/troubl...board-scematic

[m.tech]

Here is where you can download the full schematic & boardview file to hunt down the referenced mosfets:

https://www.badcaps.net/forum/troubl...board-scematic

I found the two mosfets
pins 1 2 3 of both are shorted

I don't see pins 6 7 8 from the diagram, can you help me?
Thanks

[m.tech]

PQB11
1-5 = 1,37 M ohm
1-4 = 107 K ohm
4-5 = 6,50 M ohm


PGB12
1-5 = 13 M ohm
1-4 = 106 K ohm
4-5 = 12,75 M ohm

[mon2]

Your posted values make sense. Do not worry about pins 6-7-8 in the schematic since we know they are bonded (internally) inside the body of the mosfet to pin # 5. So if you can measure pin 5, you are good for the drain pin check.

From these values, to me, each is showing a short due to the low 1-4 resistance values.

Flux and remove PGB12 - take a pic for the orientation of the part. Then measure the mosfet again after it has cooled down. Still with this low resistance? If not, the mosfet is ok and can be placed back onto the board.

[m.tech]

Your posted values make sense. Do not worry about pins 6-7-8 in the schematic since we know they are bonded (internally) inside the body of the mosfet to pin # 5. So if you can measure pin 5, you are good for the drain pin check.

From these values, to me, each is showing a short due to the low 1-4 resistance values.

Flux and remove PGB12 - take a pic for the orientation of the part. Then measure the mosfet again after it has cooled down. Still with this low resistance? If not, the mosfet is ok and can be placed back onto the board.

I also measured the second motherboard. The one I installed today and it worked for 10 minutes until the PC installed updates.
The values are very similar.
If it is possible, for the moment I prefer to avoid unsoldering, I am not very expert for such small components

Can you help me anyway to check something else? Please

I don't understand why the second motherboard, which worked for 10 minutes, stopped working
The monitor had gone black (as if it was installing video drivers) and remained like that for several minutes. Then I forced it to turn off, and it did not turn on again

[mon2]

It is possible that the screen went black due to device driver installations but you should be able to power it back up on the next cycle. Attempt to power and boot in SAFE MODE. In safe mode, the video and other device drivers will not be loaded so if there is a video driver that is not behaving, it will not load in safe mode. On this note, the video will look very coarse and not high resolution because the video resolution will be in basic mode.

If you have this second board, check the voltage to ground at the first mosfet - check the source pins (1-2-3). Any of these pins to red meter probe. Black meter probe to ground. Meter in DC volts (30v or higher) setting.

What is the voltage to ground? It should be the adapter voltage of ~19v. Then carefully, check pin # 4 which is the GATE voltage. The gate voltage defines whether this mosfet (electronic switch) is ON or OFF.

On N-channel mosfets, the gate voltage needs to be higher than the voltage being passed between source / drain pins. Often, the gate voltage should be ~25 volts to enable this mosfet. Same for the 2nd dcin mosfet in this power path. Test the gate voltage and also the drain voltage of each mosfet. In the end, the main power rail should be ~19v and then the logic board should power on.

[m.tech]

It is possible that the screen went black due to device driver installations but you should be able to power it back up on the next cycle. Attempt to power and boot in SAFE MODE. In safe mode, the video and other device drivers will not be loaded so if there is a video driver that is not behaving, it will not load in safe mode. On this note, the video will look very coarse and not high resolution because the video resolution will be in basic mode.

If you have this second board, check the voltage to ground at the first mosfet - check the source pins (1-2-3). Any of these pins to red meter probe. Black meter probe to ground. Meter in DC volts (30v or higher) setting.

What is the voltage to ground? It should be the adapter voltage of ~19v. Then carefully, check pin # 4 which is the GATE voltage. The gate voltage defines whether this mosfet (electronic switch) is ON or OFF.

On N-channel mosfets, the gate voltage needs to be higher than the voltage being passed between source / drain pins. Often, the gate voltage should be ~25 volts to enable this mosfet. Same for the 2nd dcin mosfet in this power path. Test the gate voltage and also the drain voltage of each mosfet. In the end, the main power rail should be ~19v and then the logic board should power on.

I can't boot into safe mode, the bios doesn't even start.

I'll tell you what happened.
Today I had a motherboard identical to mine, I connected everything and started the PC. Everything started regularly. After Windows started, it started installing some updates, suddenly the monitor went black, the fan was spinning high. I waited a long time, but the monitor was still black. I tried to click the keyboard but the caps lock didn't light up.
I forced it to shut down with the power button. I tried to turn it on and it didn't turn on anymore. The same defect as the first motherboard. A white LED light comes on for a few seconds, and then turns off. I remember that when the problem occurred, the first motherboard was doing updates.
My fear is that there is a corrupted bios update on the SSD, and somehow it also ruined the second motherboard.
The motherboard has an integrated CPU. Only the SSD, RAM, battery and monitor are connected.

Same for both mosfets
Voltage on pin 1 19.94v
Voltage on pin 4 25.81v
Voltage on pin 5 19.94v

Thanks

[mon2]

Your bios may be corrupt. Request a good bios in the bios forum. However, you will need the proper tools to remove and reflash the flash chip on this board using another working PC.

[m.tech]

Your bios may be corrupt. Request a good bios in the bios forum. However, you will need the proper tools to remove and reflash the flash chip on this board using another working PC.

Is this kit okay? Thanks

[m.tech]

Your bios may be corrupt. Request a good bios in the bios forum. However, you will need the proper tools to remove and reflash the flash chip on this board using another working PC.

Hi,
I flashed the bios, but the pc did not turn on.
The white led stays on for 3 seconds and then turns off.
Can you help me? Thanks

[m.tech]

Hello everyone,
I'll recap the story.
When I press the power button, a white LED lights up for a few seconds (about 3 / 5), the monitor remains off, nothing happens. The LED turns off and there is no sign of life.

I bought a new motherboard (GPT52 LA-K201P), I installed the SSD, the RAM and the various connectors (the processor is integrated), and the PC started up correctly, it worked for several minutes, suddenly, the screen went black, the fan was spinning at full speed. I waited, but nothing happened, I forced the PC to shut down.
I tried to turn on the PC, and it no longer turns on. Same problem as the first motherboard. The LED lights up for a few seconds and then turns off, no sign of life.

Considering that the PC was performing updates, I thought it was the bios. I flashed the bios using the CH341A kit but the problem was not solved.

Now I have two motherboards that have the same problem, and I don't know what to do, I ask you for help.

On the first motherboard, I found that the +3.3VS are shorted to the GND with a resistance of 27.8 ohms. On the second motherboard, there is no such short circuit.

I thank in advance all those who will help me.