Acer Aspire 9305 not turning on, but it try!

[Pauliini]

Adapter is OK. The Power LED and power button LED lights up when I try to start the computer. Some noise from DVD also and HD running, nothing else.

Charging the battery seems to be working because the charging LED lights up and turns green when the battery is full.

I opened computer and removed the battery, display, keyboard, processor, memory, hard drive, WLAN card, DVD drive and a hard drive. Only cooling fan installed.

Then I measured the voltages and researched all of the main MOSFET if they would short-circuit. No clear shortcircuit but I measured two Mosfet where is only 15-20 ohms. reading by Fluke. Still those Mosfets voltages are OK.

All other I measured the voltages were OK, except 5V_AUX_S5, which was only 0,6V. I explore in more detail the regulator circuit U31 (LP2951CDR2G-GP).

Pin 1, and 2 0,6V
Pin 3, 3.8V
Pin 4, 0V
Pin 8, 19V

I removed carefully the circuit U31 pins 1 and 2 and then the computer will no start up, even in the context of the start button, the LED does not light up.

With cutting those pins I measured the voltages U31 circuit again

Pin 1 and 2, 19V
Pin 3, 0 V
Pin 4, 0V
Pin 8, 19V

What next?

I am not expertise but I like electronics and want to learn more.

I do not have to extract the regulator.

Is it possible somehow to investigate whether the GPU still okay.

The attached wiring diagram

[piernov]

Re: Acer Aspire 9305 not turning on, but it try!

Not a good idea to remove pin 1&2, you now get 19V on a 5V line. I don't know if it is harmful in this case but be aware that messing with the "SENSE" input can destroy things.
In the first case (pins connected), SHUTDOWN input is high and that's why there is no output. It may be Q35 which tie it to ground. It's a PNP transistor so when the voltage on the base is lower than the voltage on the emitter, the transistor turns on, ie. in this case it ties SHUTDOWN to ground. Since it's controlled by RSMRST, your problem probably lies here.

[Pauliini]

Re: Acer Aspire 9305 not turning on, but it try!

Not a good idea to remove pin 1&2, you now get 19V on a 5V line. I don't know if it is harmful in this case but be aware that messing with the "SENSE" input can destroy things.

In the first case (pins connected), SHUTDOWN input is high and that's why there is no output. It may be Q35 which tie it to ground. It's a PNP transistor so when the voltage on the base is lower than the voltage on the emitter, the transistor turns on, ie. in this case it ties SHUTDOWN to ground. Since it's controlled by RSMRST, your problem probably lies here.

You are right. I think I broke my motherboard.

I solder back to pins 1 and 2 and the switch currents on, nothing happens anymore and circuit U31 will became very hot.
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I have a second Acer 7540G which is completely silent, I will come back with it when I'm measured some voltages.

It is better to ask the experts before you try guessing the different stuff ..

Thanks anyway and you can even tell you what my trick circuits possibly broke ..