Acer Aspire 4745g power problem

[lezsimply]

Good day to everyone. I've got an acer aspire 4745g laptop which turns on then off again in just under 1 sec. When I press the power button the power led blink once then off and there is no sign of life. I need to unplug the power adapter to make the power led light again. I've tested the adapter and its ok. Power jack and its wire are ok because voltage are present on the motherboard.

Motherboard receives 19.5v. Are there any areas I need to check regarding power. I also checked the motherboard for burnt components and I see none. I also got the schematic diagram for its board. Hope someone helps. thanks!

[fddizon]

Re: Acer Aspire 4745g power problem

check for 5v 3.3v alw

saw the schematic, check PL15 5V, PL16 3V

[lezsimply]

Re: Acer Aspire 4745g power problem

thanks for the reply. checked 5v on RT8206B pin no.14 (en1) OK and 3.3v on pin no.27 (en2) OK. 5v on PL15 is 5.14v and 3v on PL16 is 3.29v. Is this ok? I also measured sw1 3.3v when pressed becomes 0.5v.

[dj_ricoh]

Re: Acer Aspire 4745g power problem

check pq63,64,65 and 66

[lezsimply]

Re: Acer Aspire 4745g power problem

thanks again. pq63 and pq64 5.18v is present, pq 65 and pq66 3.38v is also present. where else do I need to check?

[whaldsz]

Re: Acer Aspire 4745g power problem

Voltage on PL11, PL12, PL9, PL17, PL14, PL7, PL13?

[dj_ricoh]

Re: Acer Aspire 4745g power problem

check V on U40 ( W25Q32BVSSIG )

[lezsimply]

Re: Acer Aspire 4745g power problem

good day, @ whaldsz all the components you have mention pl7 ,pl9, pl11 ,pl12, pl13, pl14 and pl17 have 0v reading. Is that bad? thanks

@ dj 0v on pin no 8 on u40. thanks

[whaldsz]

Re: Acer Aspire 4745g power problem

Then check the resistance to ground of those coils and mosfets too.

[dj_ricoh]

Re: Acer Aspire 4745g power problem

good day, @ whaldsz all the components you have mention pl7 ,pl9, pl11 ,pl12, pl13, pl14 and pl17 have 0v reading. Is that bad? thanks

@ dj 0v on pin no 8 on u40. thanks

pin 8 on U40 its VDD and it shows +3V .
did you check with power on or off?
do you have tools to remove it? atleast a soldering iron.

[lezsimply]

Re: Acer Aspire 4745g power problem

ok sir whaldsz Im on it.

@ sir dj, I dont have the chance to measure u40 with power because it won't turn on. Yes I do have the tools to remove it. Is u40 the bios chip?

thanks again to both of you!

[dj_ricoh]

Re: Acer Aspire 4745g power problem

Yes thats bios chip. remove it and see if power its restore.
without bios it will not Power up but you can see if power led its stable and the battery its charging.

[whaldsz]

Re: Acer Aspire 4745g power problem

Yes thats bios chip. remove it and see if power its restore.
without bios it will not Power up but you can see if power led its stable and the battery its charging.

@dj or you mean U29 (SPI Flash)? pin 8 of U40 comes from +3V (controlled by MAIND) and would not turn on unless power button is pressed.

[dj_ricoh]

Re: Acer Aspire 4745g power problem

go on page 44 and try to find some V like the P channel fets and that isl.
can you reflow the board? did you try?

[lezsimply]

Re: Acer Aspire 4745g power problem

@whaldsz, the resistance to ground of all mentioned components are ok, low resistance. u29 pin no.8 has 3.38v reading

@ dj, haven't done any reflows on the board but I do have a hotair station just incase.

I've been reading a lot of forums regarding this laptop and the usual problem involves the gpu. I hope that is not case. thanks again.

[dj_ricoh]

Re: Acer Aspire 4745g power problem

you need to reflow but make a bottom heater to not just from top.
or you can do from top ( a light reflow) just to see if anything change.

[lezsimply]

Re: Acer Aspire 4745g power problem

Before I reflow anything, I'll be redoing every test on all components just to make sure that I haven't overlooked any readings.

This is what I got on u29 pins (ISL88731A)

pin 11 (vddsmb) = 3.3v
pin 26 (vcc) = 5.18v
pin 22 (dcin) =18.87v
pin 02 (acin) = 4.02v

are these voltages relevant to my problem? Thanks again!

[whaldsz]

Re: Acer Aspire 4745g power problem

@whaldsz, the resistance to ground of all mentioned components are ok, low resistance. u29 pin no.8 has 3.38v reading

@ dj, haven't done any reflows on the board but I do have a hotair station just incase.

I've been reading a lot of forums regarding this laptop and the usual problem involves the gpu. I hope that is not case. thanks again.

What is the lowest resistance did you measure?

[lezsimply]

Re: Acer Aspire 4745g power problem

13.9ohm on PL7 why?

[whaldsz]

Re: Acer Aspire 4745g power problem

Before I reflow anything, I'll be redoing every test on all components just to make sure that I haven't overlooked any readings.

This is what I got on u29 pins (ISL88731A)

pin 11 (vddsmb) = 3.3v
pin 26 (vcc) = 5.18v
pin 22 (dcin) =18.87v
pin 02 (acin) = 4.02v

are these voltages relevant to my problem? Thanks again!

i think not. you mentioned in your post #4 that you already have 3.3V and 5V.