HP Probook 470 G2 - white blinking - ADP_SIGNAL ?

[jajo17]

Hello, I have this laptop with a bad motherboard. The LED in the socket is blinking white, endless loop. According to the information I found on the internet, this can be caused by several reasons that I am currently investigating.

1. Damaged BIOS chip - it seems to be fine, CH341a programmer can read it
2. BIOS RTC voltage shorted to ground - it seems to be fine, around 3V
3. Damaged adapter identification circuit - I think there is a problem here, but please help explain the function

What should be the voltage on ADP_SIGNAL when using a 65W HP adapter? My calculation of the voltage divider comes out to be around 2.6V if the PQA3 transistor is OFF. And what voltage should be on ADP_A_ID ?

What is the function of PQA3? Limiting the maximal voltage - overvoltage protection? If I understand correctly, PQA3 opens if the ADP_SIGNAL voltage is about 3.6V, then the voltage between the base and the emitter is - 0.6V and the PNP transistor should open.

Transistor PQA5 IS installed, its function is also unclear to me. I also don't understand what PQA1 does?


Attached page 53 from schematics https://www.badcaps.net/forum/troubl...tic#post678633

[jajo17]

Another, basic problem found. +1.05VSP short to GND

[jajo17]

But this resistance from +1.05VSP to GND can be normal, not sure

[mon2]

Yes, this is probably the CPU vcore line and by design, the resistance will be low but no idea on what you are measuring for this rail.

What is the exact resistace to ground in ohms of +1.05VSP?

[jajo17]

+1.05 VSP to GND = 0.4 ohms according to my multimeter. I haven't tried removing the connection to +1.05VS by disconnecting jumper PJH1 yet.

I have more details about the motherboard's behavior:
Sometimes, maybe once or twice a day, it behaves more normally, the white LED on the power socket is constantly on, when the power adapter is disconnected and reconnected, it usually fails to repeat and the power socket diode flashes white again for an infinite time.

I measured the voltage on ADP_SIGNAL in both cases:

1. The diode is constantly on = 2.8 V. This corresponds to the calculated value according to the resistors in the diagram.
2. The diode is blinking= 3.5 V

The measured resistance from ADP_SIGNAL to ground is constantly about 62 k ohms, with the power adapter disconnected.

This brings me back to wondering where the hell the fault is

[jajo17]

Here is some knowledge about ADP_ID_CHK circuit https://www.badcaps.net/forum/troubl...14#post3460914

[jajo17]

The notebook still resists, I have made further measurements, please give me further advice.

BIOS chip replaced and new programmed - still same error
Voltages and resistances to GND:

• +5VDS - 5V - + 20 Kohm
• +3VDS - 3.3V - 52 ohm, too low ?
• +1.05VSP - 0V - 33 Kohm
• +1.05VS - 0V - 0.3 ohm
• +3VLP - 3.3V
• +1.35VP - 0V - 1K ohm
• 3V_PCH - 3V - 11 ohm
• +RTCVCC - 3V
• 5VS 0V - 12k ohm
• 3VS 0V - 0.3 ohm

When injecting 3VS I got up to 4A at about 2.5V, the only thing that was heating up on the board was the CPU

• ADP_SIGNAL - 3.4V
• ADP_A_ID - 2.8V

When disconnecting R270 (ADP_A_ID to SIO pin 42), the voltage dropped to the expected value calculated from the voltage divider, about 1.8V. When connected back, the voltage increased to 2.8V again, so the voltage from SIO is penetrating here, the fault is more likely not in the ADP ID circuit

• 3V_PG - 3V
• DPWROK - 3.3V
• PWR_GD - 0V
• CHRG_ADP_DET 3.3V
• ACDET pin 6 on PU102 2.6V
• SLP_S4# 0V - 82 Kohm
• SM_PG_CTRL 4V - 260 K
• RSMRST 0V
• SLP_SUS ?

All these tested with multimeter seems ok:

• PQA1
• PQA3
• PQA5

PD1 disconnected from board, no change


Whole board consumption is 20 - 30 mA

[mon2]

Multiple 3v rails are too low. They do mate with the cpu / pch. To me, the cpu is likely dead. Wait on other comments.

[jajo17]

PQM1 possible short-circuit G to S, only 2 ohm. Or bad PUM1. PQM2 has G-S resistance about 1 Mohm. +1.35VP rail.

I ordered another motherboard for compare

[jajo17]

The 2nd board arrived for comparison, I haven't tried turning it on yet, measurements showed:

+5VDS - 5V - + 20 Kohm - same
+3VDS - 3.3V - 52 ohm -> 17kohm
+1.05VSP - 0V - 33 Kohm -> ?
+1.05VS - 0V - 0.3 ohm -> same
+3VLP - 3.3V
+1.35VP - 0V - 1K ohm -
3V_PCH - 3V - 11 ohm -> 15kohm
+RTCVCC - 3V
5VS 0V - 12k ohm -> same
3VS 0V - 0.3 ohm -> same

So the PCH in first boards seems to be dead. PQM 1 or PUM1 too

[jajo17]

The second board is also defective, but in different way.

Caps lock blink once
Power socket three times white
Power button does nothing, notebook does not turn on, but voltage on power button react correctly
Bios version M74, bios chip replaced, and flashed, still same

+1.05VS - resistance to ground is also 0.3 ohm. What is typical resistance value for PCH in intel 4. generation for this power rail ?