HP 14, LA-A994P, charging light, power led on for 1 second when power button pressed

[iplaypty]

Hello everyone,

I have a HP 14, motherboard model LA-A994P. When I plug the charger there is charging light present. When I try to turn in on, the power LED turn on then turn off in about 1 second and stay off.

I did check the voltages in PU301 (IC RT8243AZQW page 37 of schematic), 3.28v and 4.58v (picture attached)

No voltages in @PJ302 (should be +3valw) and @PJ303 (should be +5valw) in page 37 of schematics.

What else should I check, how do I do it?
is PU301 ok with 4.58v?

Thanks in advance.


Mario

[tibd]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

Measure the resistance to ground on PJ302, 303. Take a good Picture for the area of Power socket and post with the cord connected, specially PD1, PD2, PD3. Measure voltages at U44 pins 75, 110, 112.

[iplaypty]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

Measure the resistance to ground on PJ302, 303. Take a good Picture for the area of Power socket and post with the cord connected, specially PD1, PD2, PD3. Measure voltages at U44 pins 75, 110, 112.

Diode Mode: PJ302 = 0.783v, PJ303 = 0.985v
Resistance Mode: PJ302 = 16.41 Kilo Ohms, PJ303 = 31.2 Kilo Ohms

U44: pin 75 = 0v, pin 110 = 3.27v, pin 112 = 0v

[tibd]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

Check for shortage at ADP_ID, at TVS diodes PD2 and PD3, at the same area check pc5 and pc6

[tibd]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

Is the PSU original?

[iplaypty]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

Is the PSU original?

yes, but not in good condition. I am using another charger, with this new charger i get 0.677v at U44 pin 75, 3.27v pin 110, 0v pin 112

[iplaypty]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

Check for shortage at ADP_ID, at TVS diodes PD2 and PD3, at the same area check pc5 and pc6

ADP_ID is not short to ground, PD2 is not short to ground. I cannot locate PD3, PC5, PC6.

actually the motherboard is LA-A995P, but the only schematic I could get is LA-A994P.

[tibd]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

PD3 can come in a smal package (0402) TVS diode, usually Close to the Power connector. Bios reprogrammed?.

[iplaypty]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

PD3 can come in a smal package (0402) TVS diode, usually Close to the Power connector. Bios reprogrammed?.

I think those are the caps. Looks fine.

[iplaypty]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

PD3 can come in a smal package (0402) TVS diode, usually Close to the Power connector. Bios reprogrammed?.

I did not reprogram the BIOS.

Does it look like a corrupted BIOS?

[iplaypty]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

PD3 can come in a smal package (0402) TVS diode, usually Close to the Power connector. Bios reprogrammed?.

Finally found it, but it's empty.

Someone else tried to fix this laptop before. Is that missing?

[tibd]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

I don't think PD3 went missing of someone else picking on this board. Seems legit from manufacturer. It main function is to supress transient voltage from getting to the board, they usually go bad in these models and can be left uninstalled or changed. So thats not the problem there. I'll see if i have the LA-A995P at my Collections, that way easier to troubleshoot.

Corrupt bios have a wide range of symtoms, but Worth trying.
Do u have any oscilloscope to see if EC_ON is produced for a split of a sec, otherwise u can attach LED diode throug resistor to that pin for testing.

[tibd]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

u can try injecting 3v at pin 13 PU301 after removing pr315 and see what happens while trying to start laptop.
couldn't find any schematics neither, might be difficult to trace stufs or the Components are the same. I can se the layout is fairly different from ur pics compaired to la-a994p.

[iplaypty]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

u can try injecting 3v at pin 13 PU301 after removing pr315 and see what happens while trying to start laptop.
couldn't find any schematics neither, might be difficult to trace stufs or the Components are the same. I can se the layout is fairly different from ur pics compaired to la-a994p.

I have tried to turn it on, and it turns on for 1 sec.

There is no +3valw on @PJ302 when is off, but +3valw is present when I turn it on (for 1 sec)
There is no +5valw on @PJ303 when is off, but +5valw is present when I turn it on (for 1 sec)

[iplaypty]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

I don't think PD3 went missing of someone else picking on this board. Seems legit from manufacturer. It main function is to supress transient voltage from getting to the board, they usually go bad in these models and can be left uninstalled or changed. So thats not the problem there. I'll see if i have the LA-A995P at my Collections, that way easier to troubleshoot.

Corrupt bios have a wide range of symtoms, but Worth trying.
Do u have any oscilloscope to see if EC_ON is produced for a split of a sec, otherwise u can attach LED diode throug resistor to that pin for testing.

I do not have an oscilloscope, but I was able to test with the multimeter.
When I press the power button i get 3.27v on PIN 13 PU301. 3.27v for 1-2secs then 0v.

[tibd]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

No need to try injecting 3 v at pin13 PU301. There is something causing U44 to reset the EC_ON signal. Without proper schematics this might be no solve but worth trying. It might be a very small cap shorted on a low Power rail and not heating causing the reset.
U said that someone else tried to fix it, is that a statment or a guess? if someone did try then i would defintely start by searching for a proper BIOS for the specific board and reprogram.
Do u have a battery with the laptop? measure EC_ON while battery attached + RAM.
Can you include a crisp and zoomable Picture for both sides of the board in HD? need to look at some Components and see if the given schematics fits for further troubleshooting. an HD Picture for the KB connector and surrounding.

[iplaypty]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

No need to try injecting 3 v at pin13 PU301. There is something causing U44 to reset the EC_ON signal. Without proper schematics this might be no solve but worth trying. It might be a very small cap shorted on a low Power rail and not heating causing the reset.
U said that someone else tried to fix it, is that a statment or a guess? if someone did try then i would defintely start by searching for a proper BIOS for the specific board and reprogram.
Do u have a battery with the laptop? measure EC_ON while battery attached + RAM.
Can you include a crisp and zoomable Picture for both sides of the board in HD? need to look at some Components and see if the given schematics fits for further troubleshooting. an HD Picture for the KB connector and surrounding.

Someone else tried to fix the laptop, but that person doesn't do board component level repair.

I do not have a BIOS programmer device. I do not have a camera for HD picture, but I will upload the best photo I can take.

I do have a regulated power supply, not sure where to inject amps to find the shorted cap.

[iplaypty]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

No need to try injecting 3 v at pin13 PU301. There is something causing U44 to reset the EC_ON signal. Without proper schematics this might be no solve but worth trying. It might be a very small cap shorted on a low Power rail and not heating causing the reset.
U said that someone else tried to fix it, is that a statment or a guess? if someone did try then i would defintely start by searching for a proper BIOS for the specific board and reprogram.
Do u have a battery with the laptop? measure EC_ON while battery attached + RAM.
Can you include a crisp and zoomable Picture for both sides of the board in HD? need to look at some Components and see if the given schematics fits for further troubleshooting. an HD Picture for the KB connector and surrounding.

I took some pictures with my phone.

The owner of the laptop told me that he was using the computer, then it suddenly turned off.

[ktmmotocross]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

If it is starting, u have 3.3 ALW so u must have EC_ON

measure short to ground and voltage when it is starting on all big grey coils and capacitors

find short to ground, low voltage /overload/, no voltage /not work/ or bigger voltage /burn/


@ in schematic means that is not used

[tibd]

Re: HP 14, LA-A994P, charging light, power led on for 1 second when power button pres

If it is starting, u have 3.3 ALW so u must have EC_ON

The only voltage he has is 3v ACIN and 3VLP, the EC_ON is being generaterd for a split of a second giving EN at pin 13 PU301 which generats 3 and 5VALW. the the KB is reseting EC_ON.


@ iplaypty
Measure voltage at ADPIN at PR1 (BOTH sides of the resistor). Resistance of PR7.
Does the CPU warm up a bit when connected?