Acer Predator Helios 300 - will not power up if battery is CONNECTED

[survivalbloke]

This was a no power initially. Thanks to your help, I discovered it was the first mosfet, so I replaced. Now, the device will power up only if the battery is NOT connected. As soon as I connect the battery, it shuts off. If I connected the battery while the device is off, it simply will not respond to the power button. I replaced the battery, and while I suppose the new battery could be faulty, I'm assuming it is not. I'm having the same behavior with the new battery. I measure .2v at the charging coil. Manually applying power to the + and - at the battery header, there is no charging happening. Thanks in advance!

Acer Predator Helios 300
Model PH315-54-748Y
SN: NHQC5AA0011440BA443400
Board GH51G LA-L181P Rev 1B

[mon2]

Review the 2nd mosfet.

[survivalbloke]

Review the 2nd mosfet.

2nd mosfet measures 19.8v on source and drain, 25.9v on gate.

[mon2]

Check the battery mosfet. Suggest to remove all power and check the resistance across the source / gate / drain pins.

[survivalbloke]

Check the battery mosfet. Suggest to remove all power and check the resistance across the source / gate / drain pins.

There are three mosfets beside the BQ chip.

PQB6: was first readin 6.5k source and drain, 125k source and gate, but now, somehow it is reading 9M source and drain, and I checked a third time and getting 7M source and drain.
PQB5: 21M source and drain, 105k source and gate
PQB2: 21M source and drain, 13M source and gate

Question about mosfets... If I have my meter in diode mode, with Red - Source and Black-Drain, I should get ~0.5v, but if I reverse that, I should get OL, correct? If that's the case, then my first DCin Mosfet is working correctly, but the second one, along with all three of the mosfets near the BQ chip show 0.45 with red on source and black on drain, but if I reverse those, I get 1.5v and it steadily increases. If I'm understanding, that is not normal, at least for N channel mosfet, correct?

[Sephir0th]

These measurements aren't conclusion when done inside of the circuit. There are always other components which interfere. This means when you want to make absolutely sure, you need to remove the Mosfets in questiin and measure them out of circuits. In-Circuit you are normally good to go as long as a Mosfet (in the DC-IN circuit) measure above 1 KiloOhms in any direction.

But generally spoken, 25V at the Mosfets gate are already enough to tell they are good.

Does battery power reach the Main power rail when connected only (without charger)?

[survivalbloke]

These measurements aren't conclusion when done inside of the circuit. There are always other components which interfere. This means when you want to make absolutely sure, you need to remove the Mosfets in questiin and measure them out of circuits. In-Circuit you are normally good to go as long as a Mosfet (in the DC-IN circuit) measure above 1 KiloOhms in any direction.

But generally spoken, 25V at the Mosfets gate are already enough to tell they are good.

Does battery power reach the Main power rail when connected only (without charger)?

Sorry for such a delayed response. Yes, I have verified battery voltage on the main rail with charger disconnected.

[survivalbloke]

Anything else I can check, or should I just give up on this board?

[SMDFlea]

Anything else I can check, or should I just give up on this board?

PR203 resistance

[survivalbloke]

PR203 resistance

.99k

[mon2]

Connect only the power adapter. Share the voltage to ground on each pin of PDB1.

[SMDFlea]

Anything else I can check, or should I just give up on this board?

Did you check PQB4

[survivalbloke]

Connect only the power adapter. Share the voltage to ground on each pin of PDB1.

PDB1:1 = 19.57
PDB:2 and PDB:3 = 19.88, which is the voltage I get at the DC jack. I'm not an expert, but shouldn't I have no voltage on +19VB with the battery disconnected?

[survivalbloke]

Did you check PQB4

PQB4 seems OK, since I'm getting charger voltage out of it. That's a correct statement, right?

[mon2]

post # 13 - correct. This DUAL diode is defective. Replace it.

[survivalbloke]

post # 13 - correct. This DUAL diode is defective. Replace it.

Odd, I replaced that diode with one off another board, but I still get charger voltage on both the inputs. Output on pin1 is 19.3v now.

[mon2]

My bad. This DUAL diode is wired to accept the input from the raw adapter voltage and other leg is from the main power rail. Often, the dual diode is with raw adapter voltage AND the other leg is from the battery voltage (not the main power rail).

Go back to the battery mosfet @ PQB2. Measure the voltage to ground on each pin (source / drain / gate). Post each measurement. Do this with the power adapter connected.

In this case, this mosfet should be DISABLED.

[survivalbloke]

My bad. This DUAL diode is wired to accept the input from the raw adapter voltage and other leg is from the main power rail. Often, the dual diode is with raw adapter voltage AND the other leg is from the battery voltage (not the main power rail).

Go back to the battery mosfet @ PQB2. Measure the voltage to ground on each pin (source / drain / gate). Post each measurement. Do this with the power adapter connected.

In this case, this mosfet should be DISABLED.

Disabled would be connecting source to gate, correct? Do I do that while the power adapter is connected?

Looks like I'm getting charger voltage on drain and .2v on source and gate.

[mon2]

No bypass tricks yet. With the adapter & battery connected, you are measuring a gate voltage of 0v2? Is this correct? If yes, this is OK since this low voltage is keeping this mosfet OFF / DISABLED. The mosfet is a N-channel part so the gate must be low to disable and higher than the voltage being passed between source / drain to enable.

Can you confirm the gate voltage again with both the adapter & battery? Then disconnect the adapter and the battery voltage should be passed onto the main power rail. Then the gate voltage will be a boosted voltage and should be higher than the battery voltage. Confirm it.

[survivalbloke]

No bypass tricks yet. With the adapter & battery connected, you are measuring a gate voltage of 0v2? Is this correct? If yes, this is OK since this low voltage is keeping this mosfet OFF / DISABLED. The mosfet is a N-channel part so the gate must be low to disable and higher than the voltage being passed between source / drain to enable.

Can you confirm the gate voltage again with both the adapter & battery? Then disconnect the adapter and the battery voltage should be passed onto the main power rail. Then the gate voltage will be a boosted voltage and should be higher than the battery voltage. Confirm it.

No, the previous reading was with charger connected only. When I connect charger AND battery, I now get charger voltage on drain and 15.3v on source and gate.