Aspire VX5-591G Wont Power On

Laptop suddenly will no longer power on. Plugging in the power supply does nothing, no LED lights up. Things I've tried:

Checked that the power supply works with a voltmeter, it is outputting 19V correctly.
Resetting the battery using the small pinhole in the case.
Removing the bottom cover and disconnected the main battery and the CMOS battery for a while.
Checked that 19V from the power supply is reaching the connector on the motherboard.
Used a bench power supply to apply 19V to where the power would normally come in, no current is being drawn from the supply at all (or at least it is less than 0.5 mA).
Removed the memory, M.2 drive, and WiFi module to eliminate possibilities they might be bad, still nothing.

Has anyone run into similar issues? Guessing there might be a bad component on the motherboard somewhere.

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jeffrimko

Forgot to mention that I've also checked that the case removal switch works using a multimeter in beep mode. Have it temporarily taped down while working on it. Had issues previously with this switch where the laptop would suddenly shut off at random because the case screws loosened over time.

Commodore_1995#

Forgot to mention that I've also checked that the case removal switch works using a multimeter in beep mode. Have it temporarily taped down while working on it

Did you check these two buttons?

Image: https://us.v-cdn.net/6029997/uploads/editor/fl/dxiq763msi6v.jpg

jeffrimko

Thanks for the quick response! Yeah, I just checked both with a multimeter. They both appear to be working properly. They both connect to ground when pressed which I'm guessing is correct.

jeffrimko

Think the rightmost switch in the picture is the case removal switch (the one just below the memory). That's the one I have taped down. Unless there is another switch somewhere that detects if the case is removed.

Commodore_1995#

There are two buttons, see:

Image: https://us.v-cdn.net/6029997/uploads/editor/qg/ij9ja876dgtc.jpeg

In some versions, there is still the battery reset button:

jeffrimko

Ah okay, just checked and the model I have does not have that extra switch. I see the empty footprint where it would be placed though. Here's a picture of the motherboard, a lot of stuff is disconnected while I investigate and I removed the tape from the SW2 switch:

Image: https://us.v-cdn.net/6029997/uploads/editor/uo/18rl8a1fqd4j.png

Commodore_1995#

Did the same problem occur when disconnecting the lithium battery and have you tested it with another ram? Do the battery and power LEDs light or flash?

jeffrimko

Tried leaving the battery disconnected then connected the power supply but no LEDs turn on and the power button is unresponsive. Unfortunately I don't have any other RAM to test with. Guessing they are not the issue though since the LEDs would likely still come on even if the RAM is removed. Guessing something is up with the power circuitry on the motherboard somewhere, maybe a bad MOSFET?

I checked the voltage of the CMOS battery also. It's 2.8V which is pretty close to the 3.0V it's supposed to be.

Commodore_1995#

I found a video in German, in which the problem is very similar, see:

https://youtu.be/oUXkb7GTm4I

Of course, the problem may also be elsewhere on the motherboard.

jeffrimko

Thank you very much for finding that video! It's useful to see how to remove the motherboard, I haven't tried removing it yet because wasn't sure if the heatsinks also had to be removed. I will take a closer look later today to see if I can find a damaged component.

jeffrimko

Haven't found a visibly damaged capacitor yet like in the video. Checked a few MOSFETs and found one that might be an issue, it has 19V on the drain and 0.2V on the source and gate. Checked this with the CMOS battery installed to make sure that didn't factor into the MOSFET turning on. The designator is PQ302, haven't tried putting a jumper around it yet.

jeffrimko

Was able to find a schematic for this motherboard. After reviewing it a bit, don't think that previously mentioned MOSFET is the issue. Going to debug a bit more later today. Will report back if I find anything.

Commodore_1995#

Have you encountered the problem?

jeffrimko

Haven't found the problem yet. Been using a multimeter in beep mode and checking around the motherboard for shorts to GND. There are a lot. Focusing only on the large inductors, there are seven that are shorted to GND: PL809, PL807, PL806, PL7201, PL1301, PL602, PL402. Unfortunately, I don't have good soldering equipment on hand to try and remove some of the inductors to isolate where the short is coming from. Still thinking about what to do next.

jeffrimko

Thinking about it more, it's strange that with so many shorts to GND that there doesn't appear to be any current drawn from the bench power supply. I even tried ramping up the voltage but never seen any current draw register. Maybe there is short circuit protection somewhere that is active. I will try tracing from the power supply jack more carefully to see if I can find anything.

Commodore_1995#

Perhaps the motherboard wiring diagram can help you.

I found this video:

https://www.youtube.com/watch?v=oUXkb7GTm4I&t=528s

jeffrimko

Update on this, I think the Skylake PCH chip may have failed. This is based on:

A number of shorted power supply lines run directly to the PCH, e.g. +1.0VALW.
When supplying 1V to one of these shorted power supply lines and limiting the current to a few amps, the PCH is the only component that seems to get warm.

So unless the PCH pulls a bunch of power lines to ground when its not powered on, the chip appears to be the issue. If it does pull a bunch of lines to ground, it makes debugging a nightmare. Either way, I likely will not attempt any further repair and will probably try to sell it for parts. Thanks again for the help!

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