Hi, I have the HP EliteBook 2540P (motherboard: LA-5251P) and there is no image (even the backlight of the screen didn't light).
When I press the power button it starts to draw 0.95A@19V and works for 10sec (without heatsink on CPU & GPU). Then after 6sec it auto starts again.
The previous owner of the laptop told me that when disassembled the laptop to change the battery bios (because the laptop didn't keep the date) then after the reassembly the laptob displaed black screen. I connect an external screen from the VGA and black screen again.
When the laptop starts I measuered on the the coils the voltages on the attached picture.
Also, I download a bios and I reprogram the chip U35 but nothing changed (before I re-program the memory chip I read it and then I compared it with the bios where I download and are not the same.
Any ideas of what maybe is the problem or where to look/measure?


PL302: 3.4V (always ON)
PL303: 5.1V (always ON)
PL502: 1.5V
PL503: 1V (always ON)
PL402: 1V
PL202: 0.9V
PL201: 0.9V
PL702: 0.9V


Bios:
https://www.alisaler.com/hp-elitebook-2 ... -bios-bin/

At the attached image (Bottom_1) you can see what voltage have each inductour).

There is a possibility the SUPER IO chip (SMSC KBC1098-NU) will be the problem?
Do you know if this chip (SMSC KBC1098-NU) is programmable and maybe need re-programming?

его не нужно програмировать
---------- Добавлено спустя 9 минут 25 секунд: ----------
флешка правильная установлена? бекап покажите?

"флешка правильная установлена? бекап покажите?" (google translate: is the flash drive installed correctly? show the backup?)
It needs the HDD or SSD drive to show the bios image?

He means is bios IC correct? And asks to show original ROM image, readed with programmer.

The file "W25Q64BV@SOIC8 - Read Bios" is the bios where I read from the bios chip and the file "hp 2540P KAT10 LA-5251P 25Q64FVSIG - BIOS From The Internet" is the bios file where I found from the internet. I compare the two BIOS files (with the program "Compare It!") and are not the same.
Maybe I didn't download and program the BIOS chip with the right BIOS?


Compare It! for Windows
https://compare-it.en.softonic.com/

BIOS where I downloaded and re-flash the BIOS chip ("hp 2540P KAT10 LA-5251P 25Q64FVSIG - BIOS From The Internet")
https://www.alisaler.com/hp-elitebook-2 ... -bios-bin/

Try this bruh, there is a lot "thanks" on post, it means firmware is 100% working:
viewtopic.php?p=214562#p214562

Thanks for the reply,
I used the bios from the link you gave me but the same thing again "When I press the power button it starts to draw 0.95A@19V and works for 10sec (without heatsink on CPU & GPU). Then after 6sec it auto starts again."
What else could be or could I check?

viewtopic.php?p=214562#p214562

Is CPU getting hot? Install heatsink and necessarily connect fan. Try to press on CPU when you turn on a laptop. Also it can be PCH issue.

I installed the heatsink with the fan and now:
1. When I press the start button the motherboard draw 0,95A and I have black screen
2. After 32sec the motherboard start to draw 1,14A
3. After 46sec the motherboard start to draw 1,38A and now the screen flashing some wide vertical lines (at the attached picture & video)

I used the BIOS from the VLAB where you suggest me, the BIOs where I download from another site and the original bios where I had read from the bios chip before flash it with another. With all the BIOS the screen flashing some wide vertical lines.

I placed one RAM at a time (it has two) and the same thing again... the screen flashing some wide vertical lines.

I used an external VGA monitor and on external monitor I have no image at all even when the laptop screen flashing some wide vertical lines.

What do you beleive is the source of the problem?

It looks like graphic card issue, but GPU integrated in CPU, therefore you cant replace it and check.
When you see vertical lines and press CapsLock, is LED glows on? POST passed?

By "POST passed" do you mean the Power-On Self-Test? If yes there is another way to check it? I am saying this because the CAPS LOCK button is missing (I will try to it with a pen).
Thanks again for your time to reply me.

You can plug usb keyboard and try same. If CapsLock react try another screen or lvds cable. If CapsLock doesnt respond most likely dead cpu.

1. I used a USB keyboard and when only I saw the white vertical lines on the screen then only the CAPS LOCK light from the keyboard turn on and off respectively when I press it. Also, I pressed CTRL+ALT+DELETE and the laptop made a restart (the screen became black and after some time 43sec show again the white lines). Show as I understand the CPU is not dead.

2. I connected an external monitor with VGA and DISPLAY port cable respectively but in both cases I had "no signal" message on the external monitor. Maybe the laptop to display on an external monitor needs a BIOS setting change and for this I don't have image on the external monitor?

3. Do you know if there is any tester/adapter where is connected on an external PC card and I connect the laptop screen to check it?

Well, you can check lvds cable just by "beeping" with Multimeter. Screen can be checked only with replacement. There is no point buying tester for single laptop. Also, VGA port will work only in OS, if you install drivers for this GPU somehow(maybe on another laptop or virtual machine idk).

I checked also the TCON board for any short but nothing I found. I will check the LVDS.

I managed to take the original disk of the laptop where the guy told me it has windows 10 installed and I placed it on the motherboard but no image on the external monitor again... neither from the VGA or from the Display port. I ordered and a new cable to be 100% that is not from the cable.
Is something else where I can do?

Its not enough hdd with windows. Necessarily installed VGA driver for this particular Intel gpu. The easyest way to find another screen. Maybe cracked or with defect, it can be 15.6 inches for example.