Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

[Christian0734]

Hello,

I have a motherboard from an HP laptop: AHL50/ABL52 LA-C701P. Idle consumption is 35 mA; when the power button is pressed, the consumption goes up to 85 mA and stays there for about 15 seconds, then returns to 35 mA at idle.
First observation: the UEFI chip is not powered (MX25L6473E). I've checked the schematic; the +3V_PCH seems to come from two MOSFETs, 2N7002 and AO3413L. However, I don't have either +3VALW or PCH_PWR-EN present. The PCH_PWR-EN comes from the EC (KB9022QD). I've tested the +3VALW_EC on a few pins and I have 3.3V on pins 22, 32, 47, 97, 98, etc. I haven't measured all the pins, just giving an idea. What's bothersome is that this doesn't match the schematic I have: "LA-C701P rev 0.1" is indicated in the title block, and on my motherboard, it says "LA-C701P rev 1.0". I don't know if that's important... Could the EC be faulty?

[Techtiger]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

confirm if the RT8243AZQW IC PWM is supplying power to coil PL 9 & 8. If not ,check the following pins of RT8243AZQW: 2, 4, 11, 12, 13, 14, and 15. There are additional testing points on BQ24735RGRR and the SIO that need to be tested, but please update first

[Christian0734]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

I have no voltage on PL9 and PL8. On the RT8243AZQW: 2=0V; 4=0V; 11=19V; 12=3.6V; 13=0V; 14=5V; 15=3.3V."

[Techtiger]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

Based on the results you have provided, it appears that ENTRIP1, ENTRIP2, 0V, SMPS1, and SMPS2 will not function correctly according Function Diagram of RT8243AZQW

What is the resistance in Diode mode observed across coil PL9 and PL8?

Diode mode resistance on the EC_ON pin SIO?

Have you conducted any tests to check for shorts in the two MOSFETs, PQ7 and PQ8?

Additionally, inquire about the BQ24735RGRR

What is the supply voltage for pins 4, 5, and 6

What is the supply voltage for the P1 and P2 terminals?
EC_RST# SIO voltage?

[Christian0734]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

Based on the results you have provided, it appears that ENTRIP1, ENTRIP2, 0V, SMPS1, and SMPS2 will not function correctly according Function Diagram of RT8243AZQW

What is the resistance in Diode mode observed across coil PL9 and PL8?

PL9=0 ; PL7=0

Diode mode resistance on the EC_ON pin SIO?

EC_ON = 0.020V It depends on when I measure; I've measured multiple times and get different values, but all are less than 1V

Have you conducted any tests to check for shorts in the two MOSFETs, PQ7 and PQ8?

PQ7 = OK ; PQ8 = Between gate1 and source2, there is 32 ohms The rest is OL.

Additionally, inquire about the BQ24735RGRR

What is the supply voltage for pins 4, 5, and 6

5 = 3V ; 6 = 2.5V ; 4 = 24V

What is the supply voltage for the P1 and P2 terminals?

P1 et P2 = 19V

EC_RST# SIO voltage?

EC_RST (pin 37) = 3.3V

[Techtiger]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

What is the resistance in Diode mode (PL9=0 ; PL7=0) OL? If so, then test it in continuity mode using a multimeter. EC_ON measures the resistance, not the voltage. Regarding PQ8, there is 32 ohms between gate1 and source2, which may be due to a GND effect. The only way to clear it is to take it off and test it , is the AC LED working or not ?

[Christian0734]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

What is the resistance in Diode mode (PL9=0 ; PL7=0) OL? If so, then test it in continuity mode using a multimeter. EC_ON measures the resistance, not the voltage. Regarding PQ8, there is 32 ohms between gate1 and source2, which may be due to a GND effect. The only way to clear it is to take it off and test it , is the AC LED working or not ?

Thanks for your help.

- I might not have fully understood before. If I test to see if the coils are OK, no issue, 0 Ω. However, if you ask me to measure between the two coils, I get a resistance of 1.7 kΩ.


- EC_ON = 80 kΩ

- For MOSFET PQ8, I've desoldered it, once out of the circuit, it shows OL everywhere. And the circuit, without the MOSFET, shows 200 ohms between the Gate1 and Source2 pads.
Be careful with this 200Ω value, I feel like the measurements are fluctuating a lot. I've resoldered the mosfet and it's back to how it was before, I have 20Ω between gate 1 and source 2.

- The AC diode is on

[mcplslg123]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

Your measurement of PL9/PL7 is confusing. Put black meter probe to GND,red on coil and set meter to 200K scale-now tell us the readings on both these coils.

[Christian0734]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

Sorry, I never measured the right things concerning PL9 and PL7. If it's about measuring these coils relative to ground, PL9 = 1.775 KΩ and PL7 = 11 MΩ.


I don't know if it's a good indication, but when the motherboard is powered on, only PU2 is hot, around 38°C, the rest of the board is at 22°C. When I press the power button, PU2 goes up to 45°C and the SIO chip lights up just a bit in the center and gains just 2 to 3°C more. After a few seconds, the power consumption returns to normal and the SIO returns to room temperature, and PU2 is 16°C above room temperature.

[Christian0734]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

deleted

[Christian0734]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

I'm going to retrace the history of this failure. I hadn't done it before because it seemed a bit strange to me. The owner of this computer saw a startup message indicating that the fan was not working (or was missing, he couldn't specify). He disassembled the computer, cleaned the fan and the cooling circuit, then reassembled everything, but the computer has never started again.

Where it gets surprising is that he brought it to me to recover photos from the hard drive (HDD). I take out the hard drive, plug it in, and notice it doesn't spin. I disassemble the disk's controller board and find that on the 5V power line, the resistor that acts as a fuse and the diode right after it are burned. I replace these components, but the disk still won't start, in short...

I find it strange that there was a short-circuit on the disk controller board and, at the same time, the computer won't start up.

So here we are, where I started this post: I checked for short-circuits, looked at the power supplies, noticed that the UEFI chip was not powered, etc.

[Techtiger]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

Sorry, I never measured the right things concerning PL9 and PL7. If it's about measuring these coils relative to ground, PL9 = 1.775 KΩ and PL7 = 11 MΩ.


I don't know if it's a good indication, but when the motherboard is powered on, only PU2 is hot, around 38°C, the rest of the board is at 22°C. When I press the power button, PU2 goes up to 45°C and the SIO chip lights up just a bit in the center and gains just 2 to 3°C more. After a few seconds, the power consumption returns to normal and the SIO returns to room temperature, and PU2 is 16°C above room temperature.

Most probably, there is a short circuit on that rail or PU2 itself is bad.
Measure the resistance relative to ground continuity mode using a multimeter PL202.
Test all the Gray coils ground continuity mode using a multimeter, specifically PQ204, for any short.
Observe the voltage as you press the PWRBTWN across coil PL9 and PL8 using the multimeter

[Techtiger]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

I'm going to retrace the history of this failure. I hadn't done it before because it seemed a bit strange to me. The owner of this computer saw a startup message indicating that the fan was not working (or was missing, he couldn't specify). He disassembled the computer, cleaned the fan and the cooling circuit, then reassembled everything, but the computer has never started again.

Where it gets surprising is that he brought it to me to recover photos from the hard drive (HDD). I take out the hard drive, plug it in, and notice it doesn't spin. I disassemble the disk's controller board and find that on the 5V power line, the resistor that acts as a fuse and the diode right after it are burned. I replace these components, but the disk still won't start, in short...

I find it strange that there was a short-circuit on the disk controller board and, at the same time, the computer won't start up.

So here we are, where I started this post: I checked for short-circuits, looked at the power supplies, noticed that the UEFI chip was not powered, etc.

do you have a bench power supply ? Measure the resistance relative to ground continuity mode using a multimeter UC2 pin 8 ?

[Christian0734]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

Most probably, there is a short circuit on that rail or PU2 itself is bad.
Measure the resistance relative to ground continuity mode using a multimeter PL202.
Test all the Gray coils ground continuity mode using a multimeter, specifically PQ204, for any short.
Observe the voltage as you press the PWRBTWN across coil PL9 and PL8 using the multimeter

PL202 = 2.6 MΩ

Mosfet PQ204 all is OL

PL11 = 318 Ω
PL9 = OL
PL8 = 12 Ω
PL803 = 10 Ω
PL802 = 10 Ω
PL17 = 19.8 Ω
PL14 = 18.5 Ω
PL202 = OL

Current in PL9 when pressing the power button = 0.6 V
Current in PL8 when pressing the power button = 0 V

do you have a bench power supply ? Measure the resistance relative to ground continuity mode using a multimeter UC2 pin 8 ?

Yes, I'm using a bench power supply. As for UC2, that was the first thing I noticed; the chip is not getting power.

[Techtiger]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

PL202 = 2.6 MΩ

Mosfet PQ204 all is OL

PL11 = 318 Ω
PL9 = OL
PL8 = 12 Ω
PL803 = 10 Ω
PL802 = 10 Ω
PL17 = 19.8 Ω
PL14 = 18.5 Ω
PL202 = OL

Current in PL9 when pressing the power button = 0.6 V
Current in PL8 when pressing the power button = 0 V

PL8 ( +5VALWP LINE ) resistance relative to ground 12Ω low (starting with low voltage, 1V, and gradually increasing the amperage). do the same for PL9 Also, check for anything that gets hot. Do you have a thermal camera?"
or replace PU2

[Christian0734]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

PL8 ( +5VALWP LINE ) resistance relative to ground 12Ω low (starting with low voltage, 1V, and gradually increasing the amperage). do the same for PL9 Also, check for anything that gets hot. Do you have a thermal camera?"
or replace PU2

With 1V on PL8, I have a very low consumption of 0.075A and nothing detectable with the thermal camera.

With 1V on PL8, I have no consumption.

[Techtiger]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

With 1V on PL8, I have a very low consumption of 0.075A and nothing detectable with the thermal camera.

With 1V on PL8, I have no consumption.

try with 1.5V gradually increasing the amperage 2A

[Christian0734]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

try with 1.5V gradually increasing the amperage 2A

With 1.5V on PL9, I have no consumption (Like earlier, but I wrote PL8 twice, although I think you understood.)

With 1.5V on PL8, I have a consumption of 0.1A, and PU2 heats up very slightly, a few degrees more.


I didn't increase the voltage gradually since PU2 showed that it was the one absorbing the current. Should I go up to 2A consumption to check if anything else is consuming?

[Techtiger]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

With 1.5V on PL9, I have no consumption (Like earlier, but I wrote PL8 twice, although I think you understood.)

With 1.5V on PL8, I have a consumption of 0.1A, and PU2 heats up very slightly, a few degrees more.


I didn't increase the voltage gradually since PU2 showed that it was the one absorbing the current. Should I go up to 2A consumption to check if anything else is consuming?

You can, but sometimes it can damage other components. Measure the resistance of PC43 most of the time, bipolar capacitors fail. Are PJP2 and PJP3 jumpers present on the motherboard?

[Christian0734]

Re: Power Issue on HP AHL50/ABL52 LA-C701P Motherboard - UEFI Chip Not Powered

You can, but sometimes it can damage other components. Measure the resistance of PC43 most of the time, bipolar capacitors fail. Are PJP2 and PJP3 jumpers present on the motherboard?

The jumpers PJP2 and PJP3 are present.

The capacitor PC43 shows a reading of 50 Ω. However, I did not remove this capacitor from the circuit when making this measurement. Thus, this value might be influenced by other components in the circuit.

To clarify, the negative terminal of the capacitor is connected to ground, and from the positive terminal to ground, I get a reading of 50 Ω