[SOLVED] PC not turning on after PSU upgrade causes spark in fan connector

Apr 28, 2021
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I have an Acer Predator G3-710 that was experiencing very loud fan noise all of a sudden. After I decided that it is not worth to replace the fan inside the PSU and I just bought a EVGA GQ 850W from Bestbuy and went ahead with replacing the noisy PSU (that is a $150 PSU for a $1200 preconfig drawing probably 200W max, from Costco like 4 years ago, but I needed to work and the noise was making it really hard to concentrate, so anyways).

Then there comes the problem. I have replaced the PSU and then tried to turn on the machine, which I left the cover open for observation. The machine turns on, but I see that there is a spark occurring at the connector to the motherboard for powering fans (#15 in the following image). I think I may not have connected firmly enough because it is in a very hard to reach area in terms of wiring, and I immediately shut the power down and reconnected the wiring to the connector, but the machine no longer powers on.

When I unplug the 4pin wire, the connecting part does smell off (different from a different end of the PERIF connector, maybe smells "burnt"?).

What I mean by no longer powers on, is that:

  1. When I connect to power, the LAN light turns on. Since the motherboard doesn't have any other indicator light, I take this to mean that the motherboard is getting power from the 20+4.
  2. When I press the power button, I can immediately hear one/two faint click(s) from the PSU, but there is no fan spin from either the PSU or the CPU fan.
  3. The power indicator light does not turn on (even briefly) after I press the power button.
Things I have tried:

  1. drain the power for the motherboard
  2. use a different end of the PERIF connector provided by EVGA
  3. short the power button lines to start
All leads to the same outcome.

Things that I am thinking of trying (but haven't got the time to do):

4. put the original PSU back in to see if it still work

What exactly went wrong? Have I fried my motherboard big time? Is there anything I can still do to savage this situation?


 

TheJoker2020

Proper
Oct 13, 2020
198
45
120
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The "spark" could very well have come from one of the many onboard components where the difference of 1v is massive, or quite possibly from a short circuit.

Whatever you do, unplug the power and do not plug it back in, I have seen fires in PC's before and once something like this has already happened it only gets worse with adding more power, and it can fry your Power supply with a short circuit in the motherboard going up the power connectors back to the power supply.

Off topic a little: I literally got hit in the face once (from a couple of ft) by an exploding MOSFET on a PC I was in the process of diagnosing.

Do you have another working PC.? If so you are going to need to take out the Hard Drive, and backup your data.
 

Darkbreeze

Retired Mod
Any sign that your psu was previously opened and then returned? Because this is something that happens a lot at places like Best Buy and Microcenter.

If not, and it was fully sealed, then I would try simply disconnecting the fan connector, then see if it powers on or not.

It might also be prudent to visit the Acer forums to get more specific information regarding the pinout of the fan headers, because a lot of prebuilt systems use proprietary pinout designs and fans on their products and it's possible you either have yours backwards OR connected to the wrong fan header. Or have it over by one pin, or reversed.
 

TheJoker2020

Proper
Oct 13, 2020
198
45
120
22
When I unplug the 4pin wire, the connecting part does smell off (different from a different end of the PERIF connector, maybe smells "burnt"?).
Sorry to tell you this, but that "burnt" smell is a bad omen, a REALLY bad omen :(

Do NOT plug the power in at all...

Stick your head in the case and have a good sniff around, identify whether the smell is coming from the PSU or the motherboard.

If it is the PSU, it is dead, RMA it, AND the motherboard my also be dead. If it is coming from the motherboard then the motherboard is I am afraid dead.!
 
Apr 28, 2021
5
1
15
0
Any sign that your psu was previously opened and then returned? Because this is something that happens a lot at places like Best Buy and Microcenter.

If not, and it was fully sealed, then I would try simply disconnecting the fan connector, then see if it powers on or not.

It might also be prudent to visit the Acer forums to get more specific information regarding the pinout of the fan headers, because a lot of prebuilt systems use proprietary pinout designs and fans on their products and it's possible you either have yours backwards OR connected to the wrong fan header. Or have it over by one pin, or reversed.
The shrink wrap around the box seemed to have been damaged, but the seal remains intact and I do believe that the PSU is brand new. I will try to find out more information regarding the pinout of the fan.
 
Apr 28, 2021
5
1
15
0
Sorry to tell you this, but that "burnt" smell is a bad omen, a REALLY bad omen :(

Do NOT plug the power in at all...

Stick your head in the case and have a good sniff around, identify whether the smell is coming from the PSU or the motherboard.

If it is the PSU, it is dead, RMA it, AND the motherboard my also be dead. If it is coming from the motherboard then the motherboard is I am afraid dead.!
With the amount of wires in the case, it is a bit difficult to say the least to have a sniff around... it's pretty hard even to plug in the fan connector...

The smell doesn't seem to be coming from the PSU tho. The smell I describe is through sniffing the motherboard-end of the PERIF cable. The spark seem to also have originated from where the PERIF wire connects to the motherboard. I am totally dumbfounded as to why this would occur. Isn't spark only generated by DC voltage of at least a few thousand?
 

TheJoker2020

Proper
Oct 13, 2020
198
45
120
22
The "spark" could very well have come from one of the many onboard components where the difference of 1v is massive, or quite possibly from a short circuit.

Whatever you do, unplug the power and do not plug it back in, I have seen fires in PC's before and once something like this has already happened it only gets worse with adding more power, and it can fry your Power supply with a short circuit in the motherboard going up the power connectors back to the power supply.

Off topic a little: I literally got hit in the face once (from a couple of ft) by an exploding MOSFET on a PC I was in the process of diagnosing.

Do you have another working PC.? If so you are going to need to take out the Hard Drive, and backup your data.
 
Apr 28, 2021
5
1
15
0
The "spark" could very well have come from one of the many onboard components where the difference of 1v is massive, or quite possibly from a short circuit.

Whatever you do, unplug the power and do not plug it back in, I have seen fires in PC's before and once something like this has already happened it only gets worse with adding more power, and it can fry your Power supply with a short circuit in the motherboard going up the power connectors back to the power supply.

Off topic a little: I literally got hit in the face once (from a couple of ft) by an exploding MOSFET on a PC I was in the process of diagnosing.

Do you have another working PC.? If so you are going to need to take out the Hard Drive, and backup your data.
Thank you for your advice. I will unplug the power from now on and try to backup the data.
 
Reactions: TheJoker2020

Darkbreeze

Retired Mod
I think it's pretty likely that something is simply plugged in wrong, or plugged into the wrong place. I would double, and triple check to ensure you have things plugged or attempted to be plugged, into where they actually belong and that they are correctly seated on the right pins.

Obviously, and this SHOULD go without saying, with the power off. Just as obviously, you WILL need to power back on to determine if any changes have effected a resolution, unlike what was mentioned previously about turning the power off and leaving it off. If something is done, it's already done. There's no way you're going to figure out what's going on without making the attempt.
 
Reactions: Krotow
Apr 28, 2021
5
1
15
0
Hold up a sec, what exactly was wired to that header? You mentioned a peripheral cable, you didn't wired a Berg to that header.... right?
It is labeled PERIF from the PSU and into a molex adapter and into this presumably 4-pin connector for fan. I am not quite sure what a Berg is...
 

Darkbreeze

Retired Mod
A Berg connector. Meant for use with VERY OLD systems that have floppy drives.




And if THAT is what you are trying to plug into one of the fan headers, then there's little surprise you're getting sparks and the system won't boot. Yes, it looks somewhat similar to a fan connector, but it isn't one. If the cables don't run DIRECTLY to a fan, then it should not be plugged into a fan header, of ANY kind, unless it runs directly to a fan controller. Anything that connects to the power supply, whether directly, or through an adapter, should NEVER be plugged into any fan header. Ever.
 

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