2x Acer A517-51G not powering on.

[dr.thodt]

Hi,

I hope you can help me on this one, since I'm stuck. Never seen this behavior before.

From two different customers, within one week time I received an Acer Aspire A517-51G. Both have the exact same defect description: Won't power on.

After receiving the second unit I started suspecting a bios update, so I downgraded one machine back to 2018. Did not make a difference.

I did some measurements which might hopefully give any of the gurus here an idea.

As seen with a thermal camera:

PU301 (BQ24735RGRR):
Getting hot only while both adapter and battery are connected (33 Celsius).

UL2 (RTL8411B-CGT):
Radiating heat through the board when receiving voltage.

Voltage measurements on the two inductors that have a reading greater than 0V:

PL302:
Battery	16.45
Adapter	3.16
Both	16.8

PL401:
Battery	5.23
Adapter	5.23
Both	5.23

BQ chip has been replaced which changed nothing.

I have a working laptop which is almost similar, which does not have a seperate GPU on board. PU301 and UL2 were compared.

Voltages with adapter inserted:

	known good	suspect (with replaced BQ chip)
PU301
1	19.61		19.6
2	19.51		19.5
3	19.5		19.5
4	25.4		25.5
5	3.26		3.26
6	2.58		2.56
7	0		0
8	3.299		3.303
9	3.299		3.303
10	0.786		0.783
11	3.127		3.133
12	3.116		3.122
13	3.116		3.122
14	0		0
15	0		0
16	6.06		6.07
17	5.86		5.87
18	3.118		3.122
19	3.116		3.122
20	19.2		19.2

UL2
1	1.68		1.67
2	1.68		1.67
3	0.98		1.01
4	1.68		1.67
5	1.68		1.67
6	1.68		1.67
7	1.68		0
8	0.99		1.01
9	1.68		1.67
10	1.68		1.67
11	3.33		3.37
12	3.33		3.37	
13	0		0
14	0		0
15	0		0
16	0		0
17	0		0
18	0		0
19	0		0
20	0.99		1.01
21	0		0
22	0		0
23	0		0
24	0		0
25	0.4		1
26	0.4		1
27	3.33		0
28	0		0
29	0		0
30	3.33		0
31	3.1		0
32	3.33		3.37
33	0.99		1.01
34	0		0
35	3.33		3.37
36	0.99		1.01
37	3.33		3.37
38	3.33		3.37
39	3.33		3.37
40	3.33		3.37
41	3.33		3.37
42	3.28		3.33
43	0		0
44	0.8		0.82
45	0.5		0.8
46	0.99		1.01
47	0.62		0.62
48	3.32		3.37

What I noticed is that the known good, which does not have a seperate GPU has more voltages going on UL2 than the two "dead" machines which do have a seperate GPU.

Any help, hints or even solutions are highly appreciated.

[mon2]

Re: 2x Acer A517-51G not powering on.

The charger IC looks ok but you are missing some signals on the LAN. For example, the LAN is being held in reset mode (ie. pin #30 is LOW = PLT_RST_BUF#). This signal is driven by a buffer (UC3) that is powered by +3VS power rail. So suspecting that you are missing some required power rails that are stopping the boot up of the logic board.

Confirm if UC3 is being powered (pin #5). Confirm the voltage @ pin #1&2 of this UC3 gate.

Review the power rails in the schematic on page #4/57.

[mcplslg123]

Re: 2x Acer A517-51G not powering on.

Do you mean mb is turning on but not giving display or not turning at all?

[Sephir0th]

Re: 2x Acer A517-51G not powering on.

In my opinion it is better to have a overview about present voltage before digging in anywhere. If something points into the direction of the LAN controller, even better.

[dr.thodt]

Re: 2x Acer A517-51G not powering on.

The charger IC looks ok but you are missing some signals on the LAN. For example, the LAN is being held in reset mode (ie. pin #30 is LOW = PLT_RST_BUF#). This signal is driven by a buffer (UC3) that is powered by +3VS power rail. So suspecting that you are missing some required power rails that are stopping the boot up of the logic board.

Confirm if UC3 is being powered (pin #5). Confirm the voltage @ pin #1&2 of this UC3 gate.

Review the power rails in the schematic on page #4/57.

Thanks for taking the time.
UC3 is not populated on this board and there's no voltage on any of its pads.
UV2 is directly connected to pin 30 of UL2 and there's no voltage there.

[Plague]

Re: 2x Acer A517-51G not powering on.

Hi

Ever sorted this out. I have exactly the same problem. I took the notebook apart for cleaning and it will just not boot. I have done thousands but never experienced this

Grtz