hp elitebook 840: lights up halfway

[byroberta]

Hi, I have a problem with a hp elitebook 840: connecting the power supply, only the LED lights up. And from the button does not turn off. The CPU heats up. Screen is off.

-I replaced a cracked capacitor on 3.3v
-On the motherboard there are only 19v, 5v, 3.3v 1.05v
-I reprogrammed the two bio chips.

But nothing has changed.

[harshana]

Re: hp elitebook 840: lights up halfway

Have you check Schematics? I have a laptop with same issue.

1. Make sure EC has the voltages it need. Measure them.

2. If voltages are okay, RSMRST# and SLP_S5# Signals should present after power button press. What are the voltages there?

[byroberta]

Re: hp elitebook 840: lights up halfway

Hi, thanks for the answer.
3.3v on the EC is present
RSMRST # and SLP_S5 # are always at 0v

[harshana]

Re: hp elitebook 840: lights up halfway

Hi, thanks for the answer.
3.3v on the EC is present
RSMRST # and SLP_S5 # are always at 0v

How many bios chips are there? and what are the voltages at pin 8 of those bios chips

can you mention motherboard model? if you have correct schematics share them also.

[byroberta]

Re: hp elitebook 840: lights up halfway

There are 2 bios chips, on pin 8 there are 3.3v

motherboard: 6050A2560201-MB-A02

[harshana]

Re: hp elitebook 840: lights up halfway

There are 2 bios chips, on pin 8 there are 3.3v

motherboard: 6050A2560201-MB-A02

What is the voltage at PWRBTN?

[byroberta]

Re: hp elitebook 840: lights up halfway

PWR_BTN_OUT 3.3v -> 0v
PWRBTN 2.5v -> 0v

By connecting the power supply and without pressing anything, the LED lights up. Pressing the button does not turn off the computer

[harshana]

Re: hp elitebook 840: lights up halfway

PWR_BTN_OUT 3.3v -> 0v
PWRBTN 2.5v -> 0v

By connecting the power supply and without pressing anything, the LED lights up. Pressing the button does not turn off the computer

How much Amps taken by the motherboard???

Edit: remove all the power. measure resistance between PWRBTN and ground.

[byroberta]

Re: hp elitebook 840: lights up halfway

the motherboard draws 450mA
the resistance between PWRBTN and ground is OL. and 100kOhm if I press the power button

I'm afraid the EC is damaged!

[harshana]

Re: hp elitebook 840: lights up halfway

the motherboard draws 450mA
the resistance between PWRBTN and ground is OL. and 100kOhm if I press the power button

I'm afraid the EC is damaged!

Which part heats up. CPU or PCH??

remove all the power, measure resistance of all the coils to the ground.

[byroberta]

Re: hp elitebook 840: lights up halfway

Have you check Schematics? I have a laptop with same issue.

Were you able to fix your laptop?

[harshana]

Re: hp elitebook 840: lights up halfway

Were you able to fix your laptop?

Unfortunately Im not able to fix. as I identified PCH has fried. here is that thread for your reference.

https://www.badcaps.net/forum/showthread.php?t=110115