Acer Aspire E5-574G - Not Powering On

[mcplslg123]

Re: Acer Aspire E5-574G - Not Powering On

Yes, 1.35Vsus rail is shorted to GND and you need to inject 1V/5A on Pad2 of PL15.
Cant say for sure how long will it take for shorted component to heat up-it varies from board to board. You can keep it injected for longer duration say 10 mins if u cant feel what is getting hot.

The most worrying part is that the short may be in CPU as this rail goes to cpu.Lets hope for the best.

[novice1]

Re: Acer Aspire E5-574G - Not Powering On

Thanks for the confirmation. I started by injecting 1V/5A but nothing was getting hot at all. So I increased the current to 8A, the only component that got hot was the CPU, and then later after sometime the other side of the board area below it. But the side where the CPU is the hottest. To know what side is warming up faster, I placed fingers on both the CPU side and the other side of the board right below it at the same time. I believe the CPU side gets hot first, and then the other side of the board area right below it starts to get warm. The other side is less hot than the CPU though but it eventually does get slightly hot after the CPU gets hot. There are a lot of capacitors on that side but none look visually damaged. For example C286, C289 and so on. I ran this about test 5 times and will probably do it again tomorrow. You're probably correct, that short is in the CPU.

Since I was still in complete denial that CPU is shorted/fried, I performed another test using the freeze spray. I used freeze spray first on the CPU side, and as soon I injected voltage the freeze started to melt, like immediately right on top (metallic part) of the CPU is where it starts. But on the other side of the board in the area below the CPU, it takes like 10 to 15 seconds for the freeze spray to start to melt. Moreover the melting doesn't start on any components (mostly capacitors) but on the stitching right next to capacitor C289. Then after that it spreads to capacitors around that area. I guess this is because the board area on CPU side gets hot and eventually heats up the other side of the board. You can also see on the board view that there is an empty area on the other side of the board right next to C289, and below C246, C269, C214. I can visually confirm the delay as to when the melting starts on the other side of the board.

I might have inadvertently shorted the CPU while trying to learn on my own about schematic, board view and other stuff over the past 3 months. I was always measuring voltage on Pins by connecting AC adapter to the DC jack which is like injecting 19V. Even though I never removed any component while doing so, I guess it could still cause it.

No component looks visually damaged, I used a powerful lens to look at them closely. Not sure if there is way to fix this. I definitely feel less enthusiastic because the CPU is soldered to the board. Please correct me if you think anything I did was incorrect, and I will do so again. I would like to be wrong in this case and get this fixed. I will wait for your response as to if anything could be done here. Thanks again.

[mcplslg123]

Re: Acer Aspire E5-574G - Not Powering On

Unfortunately, this is a lost case and its wiser to give up. A short to GND on 1.35V rail is most often coz of shorted memory controller inside CPU. Have seen such case on many occassions.

[novice1]

Re: Acer Aspire E5-574G - Not Powering On

Thanks, and I agree with you. There is no point as the CPU is soldered to the motherboard. It will take a lot of skill and precision to de-solder and then solder a new CPU.

Thank you very much mcplslg123 for your help. I learned a lot from you and piernov's guide as well. I didn't have much knowledge or experience but you were always very kind, and patient. Always responded as well. Much appreciated. Next time if anything like this happens it will be resistance mode all the way, and probably not use 19V AC adapter to burn things up. I honestly understand things a lot better now.

I have another question just to learn as that is one of the things I don't fully understand. Can you tell me which N channel MOSFET on this board what would be a high side MOSFET, and which would be a low side MOSFET. So for example: Is PQ31 (near PL15) on Page 35 of the schematic a low side MOSFET since source is directly correctly connected to the ground while the neighboring PQ32 is high side N channel MOSFET? Is PQ22 on Page 30 a high side MOSFET as well since source is not directly connected to the ground? I would like to know a few examples based on this schematic. I'm not sure, and would like to understand the concept by looking at the schematic as to how to know which is which.

[mcplslg123]

Re: Acer Aspire E5-574G - Not Powering On

PQ32-High side(as VIN comes on Drain)
PQ31-Low side
PQ22 is DC-in mosfet-so nothing like high or low side here.

I suggested not to continue with this repair as soldering a new cpu requires a lot of expensive tools(like bga rework station) and to add to the misery is non availability of reliable new cpu.Skill is another factor. You can get a new motherboard at competetive price instead of going thru all this hassle.