FPC52 LA-H462P 0.3v instead 1.8v on VCC BIOS

[TonyCajeta]

Hello there,

I'm having a terrible time with an HP Pavilion Gaming, my customer just wanted a thermal paste replacement so i did it like always, i thought everything was fine, disconnected the battery before, use anti ESD gloves, work on a nonconductive surface and it is not the first laptop i do maintenance work.

Well... now the laptop won't boot, no video, i just click the PWR BTN, lights on for 5s then off, no fans spinning, no CPU voltage nor GPU nor RAM 1.2v.

I just have, AC IN 19.5v / 3.3VALW / 5VALW / 1.8VALW / 1.05VALW.

I'm not an expert but i checked the BIOS VCC and it has 0.28-0.3v when the chip vcc should be like 1.8v.

I don't know what to do, it is so hard working without squematic, have just the boardview, it seems to me 1.8 BIOS VCC is connected somehow to the 1.8v GPU and has some relation with the HDMI/DP Ports.

I suspect is not a badcap bc i inject 1.8v on BIOS VCC pin and the current draw is about 0.003 A. maybe a faulty MOSFET?

Man, I'm really sad about this, i would have to pay like 400usd for a new MB if i can not repair this... I can't figure out what TF damaged it in first place, i saw it working, boot windows normally, now it's a potato.


Below, i share you the Boardview of this model. PLS HALP !

[mon2]

Re: FPC52 LA-H462P 0.3v instead 1.8v on VCC BIOS

Will barter for a good veg recipe for chilli con conqueso dip recipe.

Remove all power. Check the obvious points of interest.

The dcin adapter connector. Connection is solid?

Connect the power adapter.

What is the voltage to ground at the dcin connector?

After the DCin connector will be 2*DCin mosfets. They act like solid state switches or relays to power the logic board. The output of these mosfets should be ~19v.

Measure the voltage to ground of these mosfets.

Source pins are grouped 1-2-3.
Gate pin in pin #4.
Drain pins are grouped 5-6-7-8.

Check each pin group voltage to ground.

Meter in resistance mode. Check the resistance to ground of the bios voltage pin that you suspect to be low.

What is the resistance?

Do check that the power button is working ok.

PS: do not inject voltage till more is known. This can kill the board. Injection should be as high as the lowest voltage rail which is 1 volt. This is to save the CPU in case a mosfet is leaking. The injection voltage can reach the CPU.

[TonyCajeta]

Re: FPC52 LA-H462P 0.3v instead 1.8v on VCC BIOS

Will barter for a good veg recipe for chilli con conqueso dip recipe.

Remove all power. Check the obvious points of interest.

The dcin adapter connector. Connection is solid?

Connect the power adapter.

What is the voltage to ground at the dcin connector?

After the DCin connector will be 2*DCin mosfets. They act like solid state switches or relays to power the logic board. The output of these mosfets should be ~19v.

Measure the voltage to ground of these mosfets.

Source pins are grouped 1-2-3.
Gate pin in pin #4.
Drain pins are grouped 5-6-7-8.

Check each pin group voltage to ground.

Meter in resistance mode. Check the resistance to ground of the bios voltage pin that you suspect to be low.

What is the resistance?

Do check that the power button is working ok.

PS: do not inject voltage till more is known. This can kill the board. Injection should be as high as the lowest voltage rail which is 1 volt. This is to save the CPU in case a mosfet is leaking. The injection voltage can reach the CPU.

lol yeah, i'll find out the best chilli recipe hahah

Well... let's see

DC-IN Adapter connector on mainboard is ok, 19.73v.

Mosfets at entrance same 19.73V (PQB01 and PQB03)

* Resistance to ground of the BIOS VCC pin: 24.2 kOhm

* Power button is working perfectly.

You have reason about inject voltage, i started with 1v but didn't see any important current draw, then just raise to 1.8v

[mon2]

Re: FPC52 LA-H462P 0.3v instead 1.8v on VCC BIOS

Can you link a schematic if available?

The resistance is ok and is not a short.

Which charger IC is onboard?

[TonyCajeta]

Re: FPC52 LA-H462P 0.3v instead 1.8v on VCC BIOS

Can you link a schematic if available?

The resistance is ok and is not a short.

Which charger IC is onboard?

Sadly, no schematic available, just the boardview i attached above.

Charger IC Intersil ISL88739A

[SMDFlea]

Re: FPC52 LA-H462P 0.3v instead 1.8v on VCC BIOS

Sadly, no schematic available, just the boardview i attached above.

Charger IC Intersil ISL88739A

UH2 is the bios chip ,+3V_SPI .Check all the connectors on the board,the ribbon cables especially, make sure the gold fingers aren`t bent over,broken or missing.

[TonyCajeta]

Re: FPC52 LA-H462P 0.3v instead 1.8v on VCC BIOS

UH2 is the bios chip ,+3V_SPI .Check all the connectors on the board,the ribbon cables especially, make sure the gold fingers aren`t bent over,broken or missing.

Oh.. i think i f***ed up the situation,

i commited the big mistake supposing the BIOS chip was the Winbond 25q80ewsig (UG109). But you're right, BIOS is UH2 and i have +3V_SPI there.

I have flashed the UG109 chip with the main BIOS program omg i think at this point it is not possible to recover the original program for this chip right? i mean i don't have the BIN file for this chip.

... Then the problem may not be BIOS related

[mon2]

Re: FPC52 LA-H462P 0.3v instead 1.8v on VCC BIOS

Found these through Bolo's extensive Google fu training.

Bios -> https://www.badcaps.net/forum/showthread.php?t=116460

Try the EC OK image for the low density flash that was overwritten.
.

[SMDFlea]

Re: FPC52 LA-H462P 0.3v instead 1.8v on VCC BIOS

Found these through Bolo's extensive Google fu training.

Bios -> https://www.badcaps.net/forum/showthread.php?t=116460

Try the EC OK image for the low density flash that was overwritten.
.

UG109 isn`t there. Ive seen it on a paid forum and at vlab, hopefully someone will post it

[TonyCajeta]

Re: FPC52 LA-H462P 0.3v instead 1.8v on VCC BIOS

Well, i paid for it, programmed UG109 with the right BIN file. If someone need ask for it and i'll upload it (i don't post it right now bc i'm on a different computer and stuck working under preassure :sad: )

Now I'm at the start point again... Checking the voltage rails there is not present CPU nor
GPU nor RAM voltage. I think i'll check now the BIOS data in/out with the oscilloscope but i guess there should be present RAM voltage first isn't it?

[mon2]

Re: FPC52 LA-H462P 0.3v instead 1.8v on VCC BIOS

With no power to the logic board -> what is the resistance to ground of the CPU power rail?

[TonyCajeta]

Re: FPC52 LA-H462P 0.3v instead 1.8v on VCC BIOS

I have finally solved it!

As a responsible member i share with you the solution.

UH2 BIOS had a blown resistor to pin 1. it is a 0402 size resistor so it was impossible for me to notice, but doing some analysis on the BIOS since it always had BIOS related symptoms i discovered it, then searching on another schematics i see there is normally a 0 ohm resistor, so i just bridged that then it worked!.

Thank you for your replies guys, SMDFlea you saved me life telling me it was UH2 the main BIOS THANKS!

[mon2]

Re: FPC52 LA-H462P 0.3v instead 1.8v on VCC BIOS

Good job!

You are still on the hook for the chilli con conqueso dip recipe.

Hope to have some in Detroit this weekend.