HP14 - DA0G7GMB8F0 REV.F

[mon2]

Meter in resistance mode. Measure the resistance from pin #4 (gate) of each of these mosfets to pin #32 of the charger ic. We are trying to locate which one of these mosfets is being driven by the charger ic (BGATE).

[Darren Hibbert]

Ok so Pin 32 to Gate of the 21321 MOSFET is 0.3 ohms

Looking at that other MOSFET I sent a picture of, I just noticed it has 2 gates so maybe I never measured that one properly. Hopefully the 21321 MOSFET is the one we are looking for.

[mon2]

Yes, 21321 is the battery mosfet and the resistance check looks to be ok.

Here is the datasheet for this P-channel mosfet:

AONR21321 Datasheet | DigiKey

Locate the high side mosfet driven by the same charger IC. We are hunting for a mosfet that is possibly leaking. The other mosfet found in the earlier post looks to be low in resistance and is a suspect. Review where the pin # 4 of that mosfet travels to the charger IC. It is possible that there will be a current limit resistor between the charger IC pin and the mosfet's gate pin.

[Darren Hibbert]

Ok pin 4 of the top (there are two) QA3112 goes to pin 7 (LGATE2) of the charger IC.

[Darren Hibbert]

Pin 4 of the bottom MOSFET goes to pin 9 (LGATE1)

[Darren Hibbert]

I'm really appreciating your help by the way 🙏🤩

[mon2]

Continue to hunt for the mosfet mated with the UGATE2 pin on the charger IC using the same method. One meter probe on UGATE2 pin on the charger IC; other meter pin on pin # 4 of the mosfet.

Once that mosfet is located, proceed to test that mosfet using resistance mode (if manual mode meter, use a higher resistance scale). If you read 'OL' = over limit, switch to a higher resistance scale on the meter.

Measure the mosfet as follows:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement.

[Darren Hibbert]

Ok so UGATE2 of the charger IC goes to the MOSFET in the picture. I'm a little confused by it as it does not have a 1234 drain. Hopefully I've measured right but I'm unsure of the different layout of pins on this chip compared to your traditional MOSFET.

Here is what I got with my effort -

Source to drain - 0.9 M ohms
Source to gate - 3.6 M ohms
Gate to drain - 500 K ohms.

[mon2]

Good point and bad assumption on my part. Consult the datasheet and measure again to hunt down the respective gate / drain / source pins for this dual mosfet.

PS: Need to make a quick trip to Detroit - BBL.

[Darren Hibbert]

Ok safe trip.

I checked the 3 pins on one side of the mosfet and they all go to Ground 🤷 (see pic)

The 3 on the other side obviously don't. The datasheet shows 3 Source pins and 3 Drain pins. 3 of these pins are grounded so I assume that MOSFET is shorted to ground?

I have a thermal cam so will try it while your on your trip and let you know the results.

[Darren Hibbert]

Thermal cam showed nothing.

[Darren Hibbert]

I did notice when I turned the laptop on, that the chipset was starting to heat up for the 3 seconds before it starts looping on and off, I assume this is normal?

[mon2]

Which chipset?

[mcplslg123]

I simply dont understand why we're after charging circuit when the system is charging battery?

The resistance to GND for cpu coils is perfectly fine-so SOC is not shorted.

[Darren Hibbert]

Which chipset?

Next to the CPU

[Darren Hibbert]

Is it at all possible that the laptop is switching on and off because of a corrupt BIOS?

[mon2]

Backup the original bios and test with a known good bios. If necessary, post your request for a fresh bios inside the bios forum.

[Darren Hibbert]

Hi.

Tried a new BIOS but the laptop is doing the same on and off every 3 seconds with no picture. Time to move on to the next step I think. 🤔

[Darren Hibbert]

On the CPU inductors, I'm getting 35 ohms. I might be wrong but that sounds high to me?

[mon2]

Can you measure the 2nd mosfet again from post # 20 and post your measurements. The first measurement looks very low for a good mosfet.

On the CPU resistance, it is not shorted with such a value.