Acer Aspire 5741G Shuts down

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Acer Aspire 5741G Shuts down

Postby matic_s » Sun Jun 18, 2017 12:40 pm

Hello!

I have here an Acer laptop, which was automatically turned ON after connecting the power supply or battery (without pressing on the power button). The customer also mentioned it sometimes shuts down automatically.

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Model: Acer Aspire 5741G
Motherboard: Compal NEW70 LA-5891P, Rev.: 1.0
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The first thing I successfully repaired with reflashing BIOS chips (MAIN + EC).
The second issue still persists. It sometimes completely turns OFF like cut out the power supply. It sometimes works for hours, sometimes shuts down few seconds after pressing on the power button.
When it automatically turns OFF it also crashes date and time settings in BIOS.

CMOS battery is ok, I also tried with another power supply and without main battery but it is nothing changed.

I found a burned capacitor PC341 on the motherboard, but after replacing it the issue still persist.
Image

Pictures of motherboard:
Image Image

I think it could be bad solder joints (or bad) PCH chip, but I'm not sure.
Any ideas?
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Re: Acer Aspire 5741G Shuts down

Postby koubik » Mon Jul 03, 2017 7:01 am

Hi. Usually PCH goes bad on this board. You may need to flash the bios with clean ME region after replacing it.
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Re: Acer Aspire 5741G Shuts down

Postby matic_s » Wed Jul 05, 2017 6:17 am

New PCH is ordered.

Thank you!
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Re: Acer Aspire 5741G Shuts down

Postby Dee30 » Wed Oct 11, 2017 7:20 pm

I think this is an issue with a signal produced by the coin battery power, rsmrst or some kind, which is needed in the first phase before pressing power button, if this signal is not present, nothing will happen, power button will not work, there are other signals as well that must be present before power button will work.

So my theory is, you have a defective component i.e diode or transistor which makes either signals intermittently low or high which may explain sudden off and date reset as that signal is ment to be always present becouse of costant power from coin battery.

Or as you say, a cold solder joint on one of these signals, I would trace all the always present signals before power button as date can only be effected on this stage.(save time and look closely first for any minute corrosion or green stuff on any components, often will be missed on just a magnifying glass, need micrsope or a digital usb scope. Without looking at schemaics I cannot go further in specifics, each board have thier own variations so you would need to study it a little.

Do let us know what happens either way, thank you.
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Re: Acer Aspire 5741G Shuts down

Postby matic_s » Thu Oct 12, 2017 1:04 pm

Excuse me, I forgot to publish the results...

So I replaced PCH chip with new one, like @koubik suggested.
After that everything worked normally. It was not necessary to clean the BIOS ME-region.

Thank you very much, koubik!

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Re: Acer Aspire 5741G Shuts down

Postby koubik » Thu Oct 12, 2017 2:04 pm

You welcome mate. Glad you've managed to repair it. :)
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