Acer Aspire 4752 Not Power on (Power & Charger LED Blinking continuously)

Model : Acer Aspire 4752
Board id : JE40 HR MB (10267-4)

First, laptop came with 19v line short. I found shorted N-Channel Mosfet (PU4503) and replace with good one. 19v line short is gone but when adapter connect, Power & Charger LED Blinking continuously and laptop cannot power on. Please help me to find the fault.

It measures the voltage and resistance to ground on all the coils.

Voltage and Resistance to Ground in all Coils
PL4001 - 0.18V 3 M
PL4101 - 3.3V Not stable in number KOhm MOhm etc ...
PL4102 - 5V Not stable in number KOhm MOhm etc ...
PL4303 - 0V 0L
PL4401 - 0v 10 Ohm
PL4301 - 0v 7.2 Ohm
PL4302 - 0v 7.2 Ohm
PL4501 - 0v 25 Ohm
PL4601 - 0v 2.3 Ohm
PL9201 - 0v 0.9 Ohm

Measure the voltages on all pins of Pu4601.
Desolder Pl4601 and measure resistance to ground on both pads.

PU4601
Pin 1 - Ground
Pin 2 - 0v
Pin 3 - Ground
Pin 4 - 0v
Pin 5 - 0v
Pin 6 - 5v
Pin 7 - 0v
Pin 8 - 0v
Pin 9 - 0v
Pin 10 - 0.1v
Pin 11 - 0v
Pin 12 - 18v
Pin 13 - 0v
Pin 14 - 5v
Pin 15 - 5v
Pin 16 - 5v
Pin 17 - Ground
Pin 18 - Ground
Pin 19 - 0v
Pin 20 - 0v
Pin 21 - 0v
Pin 22 - 4.7v
Pin 23 - 0v
Pin 24 - 0v

Pl4601 resistance to ground on both pads:
2.7 M (PWR 1D5V Phase)
2.1 Ohm (1D5V S3)

Remeasure the resistance to ground on power rail "1D5V_S3" with disconnected RAM memory and with disconnected USB/Audio board.

If after removing the components, as indicated by colleague Matic, you still have low resistance, you must do the short circuit test as described here:
post5699.html#p5699

Disconnected RAM memory and 1D5V_S3 resistance to ground is about 1 M and reduce slowly.

Connect the RAM memory and USB/Audio board one by one and check, which thing needs to be connected that the resistance drops to a low value.
It is bad one (or both) RAM memory module, or an USB/Audio board.

How can i remove USB/Audio Board. Do you mean to remove Audio IC and USB Connector?

cygron ha scritto:How can i remove USB/Audio Board. Do you mean to remove Audio IC and USB Connector?

No, just disconnect the USB/Audio board FFC cable from the motherboard for now.

Is the low resistance to ground on power rail "1D5V_S3" caused by a USB/Audio board?

No. it's not have a separate USB/Audio Board. It's combine with Motherboard.

cygron ha scritto:No. it's not have a separate USB/Audio Board. It's combine with Motherboard.

For sure? I'm talking about the board connected to the highlighted connector.

Oh i see. I already remove it. Low resistance to ground on power rail "1D5V_S3" is not caused by a USB/Audio board.

Connected with RAM memory and 1D5V_S3 resistance to ground is 4.8 Ohm.
Disconnected RAM memory and 1D5V_S3 resistance to ground is about 1M and reduce slowly.

Please take a look video for laptop error.


https://youtu.be/gm6PIEOIGc8

You have the ram in short test with another ram.

Yes. I already tested with another RAM. RAM Card is OK. Motherboard Power & Charger LED Blinking continuously with and without RAM and CPU. Please look in video. 5V 3V are on and off repeatedly. No other Voltage are not found. I think motherboard is on and off very quickly because of short somewhere in motherboard. I already replaced 5V 3V Capacitors.

Measure the voltages to ground on all coils, when the machine is turned on (LEDs are blinking) with the CPU and RAM memory disconnected.