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Old 11-20-2019, 06:35 PM   #1
Retrocomputer
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Default Acer Aspire 5552G power short

Hi!
I need some help for the laptop specified in the title.
It's owned by a friend of mine. At first, it started displaying only a black screen and fan spinning. Then he tried doing an homemade reflow on the VGA BGA. After that, it could be turned on every time for a short second with no fans nor anything (LEDS only), then shutting down (just before shutting down you can hear a slight pop on the board, source unidentified). After three or 4 attempts, he said the laptop squealed for a moment the shut down forever. Now it shows no signs of life with the AC adapter connected, the B+ shows almost short to GND (2.6 Ohms).

Mobo NEW75 LA-5911P. Schematics here: http://www.rom.by/files/compal_la-59...schematics.pdf

How can I go on diagnosing the fault?

Thank you so much!!
Davide

Last edited by Retrocomputer; 11-20-2019 at 06:36 PM..
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Old 11-20-2019, 07:33 PM   #2
surecando
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Default Re: Acer Aspire 5552G power short

MOSFETs gone
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Old 11-21-2019, 05:36 PM   #3
Retrocomputer
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Default Re: Acer Aspire 5552G power short

Thank you. Now it behaves differently. I found PQ38 shorted, replaced it and now we're like before. As soon as you press the power button (with AC adapter), the LEDS come up for a brief second then it shuts down, making a slight click/pop from an unidentified place on the MOBO. The three main always on voltage rails (+5,+3.3,+1.1) are present and constant upon connecting the adapter.

Thank you.
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Old 11-21-2019, 09:35 PM   #4
surecando
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Default Re: Acer Aspire 5552G power short

Check your power supply see how many amps it's drawing without turning on, if it's drawing amps, you should feel which part is getting hot
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Old 11-22-2019, 08:46 AM   #5
piernov
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Default Re: Acer Aspire 5552G power short

GPU reflow → dead. You already know where the fault lies.
This is gonna have a dead northbridge anyway.
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Old Yesterday, 06:37 PM   #6
Retrocomputer
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Default Re: Acer Aspire 5552G power short

Hi, just for curiosity sake I decided to remove both the IGP and the VGA. (Then reinstalled a couple reballed ones). The short is still there. PQ38 is shorted at D/S terminals (B+/+VGACOREP), no power at all now. PR124 to 127 become slightly hot. PQ31-33-34 already checked and not shorted. It's just to see if it lives again... thank you.
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