Acer Nitro 5 AN517-52-5744 - Not Powering On

[bialag]

Hello guys,

I have a Nitro 5 motherboard that is not powering on. When I connect 19.5v from the power supply, I get 3.3-3.8v where the charging port AC-in is supposed to be. For the supply and gate of the MOSFET I get the same 3.3-3.8v and at the drain 1.3v. The 3.3-3.8v jumps up and down with and without the MOSFET installed.

There is also a PQB11 where I get 1.3v at pin 1 and 0v and -15v for the other pins.

All this with 0 amps being drawn. Any ideas?

Board number: FH51M LA-J871P Rev: 1B 2020-06-04

[mon2]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

You are measuring -15v ? There should not be any negative voltage rails on the power paths. Only the rs232 transceiver charge pump will have ~6 volts with a positive and negative swing.

Review the voltage to ground of each pin on the charger IC at PUB1. Connect both the power adapter and the battery.

Post the measurements and their pin numbers.

[bialag]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

Hello, here are the voltages. A lot of these seem very low.

1. 0v
2. 0v
3. 0.290v
4. 0.270v
5. 0v
6. 0.410v
7. 0.010v

8. 0.250v
9. 0.530v
10. 0v
11. 0.020v
12. 0.010
13. 0v
14. 0v

15. 0.010v
16. 1.280v
17. 0.141v
18. 0.900v
19. 0.133v
20. 0.133v
21. 0.490v

22. 0v
23. 0v
24. 0.375v
25. 0.470v
26. 0.152v
27. 0.141v
28. 3.09v

[mon2]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

See attached. Review the VCC (power) pin # 28.

Nearby should be a 3 pin dual common cathode diode.

Attach your power adapter.

Measure voltage to ground of each pin. Post the measurements.

[bialag]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

Thanks for the quick reply.

1. 3v
2. 0v (+19VB)
3. 3.3v (+19V_VIN)

This is consistent with the 3.3v coming from the main AC-in pin and I'm for sure getting 19.5v from the power supply.

[mon2]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

See attached. Review the raw voltage from the power adapter.

Is it ~19v ?

Then measure the voltage after the EMI coils. Is it still ~19v ?

[bialag]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

Hello,

I checked and both sides of the coil is 3.3 volts. Please see attached. I noticed PL102 (below PL101) was burned and so I removed. I have not replaced it yet, but 3.3v still remains on both sides of the coils. I also tested continuity from the DC-in jack where it meets the power adaptor and pin 1 that is soldered to the motherboard. Tests fine yet it is measuring 3.3 volts from ground.

[Sephir0th]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

There are not many possibilities left, since ACER usually don't use something like adapter detection.

Although you already persisted that your setup is okay (which actually makes our assistance here way harder), something should be wrong with your PSU/wires/DC-Plug/DC-Jack. Has to be ruled out one by one in any case.

It can't be a short to GND (or to whatever) since the board does not take any current, as you stated before. And I have big doubts we are dealing with a board issue here with this behaviour.

[Sephir0th]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

Burned Inductors are in my opinion a additional indicator that something is wrong with the DC-IN Jack. The second one could have failed partially too.

[bialag]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

Alright it might look like the DC-in might have something to do with it. I instead injected 19.5 volts directly after the DC-in jack and now I get 19.5 volts but still 0 amps. EMI coils have 19.5 volts on both sides and the 3 pin dual common cathode diode is now outputting 19.5 volts to the BQ chip.

I put together the motherboard and other components but unable to turn on by pressing the power button. The MOSFET near the DC-in jack shows 19.5 volts going in pins 1,2,3,4 and 0v going out pins 5,6,7,8.

[Sephir0th]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

Time to look whether the main power rail is shorted to GND. If not we have to check these DC-IN mosfets mosfets for beeing internal shorted beyween any logic. If still nothing, we have to move to the charging controller.

[bialag]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

I measured in diode mode:

DC-in 1.575

MOSFET
1.442
1.442
1.442
1.233
1.574
1.574
1.574
1.574

I also found pin 2 for PDB1 (+19VB) to be shorted to ground?

PDB1
1. 0.309
2. 0.00 *
3. 1.579

[mon2]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

Remove all power. Meter in resistance mode.

Measure the resistance to ground of pin #1 of the dual diode @ PDB1.

Then repeat for pin #2 and finally pin #3.

Post each measurement.

Pin # 2 is the power feed from your battery pack. If the battery is not dead, you should have a voltage present @ pin # 2.

For now, only interested in the resistance to ground of each pin.

[bialag]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

I measured PDB1 with battery and PSU disconnected and this is what I get:
PDB1
1. 0.309
2. 0.00 *
3. 1.579

Pin 2 is shorted to ground and battery is not connected.

[mon2]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

These are diode readings. Use the resistance mode (ohms / Omega symbol) to measure the resistance of each of these to ground.

[bialag]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

Oops.

PDB1
1. 9.45K
2. 1.5 Ohms
3. 282K

[mon2]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

As per post #11, you have a short to ground on the main power rail. 1R5 is a very low resistance.

Pin #2 of this dual diode is mated with +19VB which is the main power rail.

In the absence of the power adapter, the charger IC will enable the battery mosfet @ PQB2 to allow for the battery to power the logic board.

When the power adapter is present, PQB2 will be turned off and both DCin mosfets (PQB3 & PQB4 will enable if the gate voltage is boosted to ~25v) will be turned ON to power the logic board and also charge the battery pack.

Given the low resistance to ground on pin #2 of the diode, there is a component that is shorting. Hope it is a capacitor and not the CPU.

Would you have an adjustable power supply that can output 1 volt?

[bialag]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

That makes sense. Should I inject 1V into +19VB and see what gets hot? I do have a thermal camera that should help as well.

[mon2]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

Yes, 1 volt will be fine. Get out that Superman camera and see who glows. Do not increase the voltage but do crank the current. We use short killer 30 product which can support 0v8 and upto 30A. Often the caps will crack at a much lower current.

[bialag]

Re: Acer Nitro 5 AN517-52-5744 - Not Powering On

I injected 1v and did not see anything until I raised it slowly to 2v and then 3v. I found PU301 to heat up quite a lot. What chip is this? I also see pin 2 of this chip is about to break off.