Question Weird no power issue on my Lenovo desktop PC ?

[alexborex]

Hello everyone, I have a Lenovo ThinkCentre M72e Desktop PC fitted into a custom case, that exhibits a really weird issue where the pc sometimes shows no signs of life after pressing the power button, and sometimes it works perfectly without a single problem.

It still has the same issue with a brand new good power supply, but i've discovered that when the pc is dead, taking it apart and replugging the 24 pin ATX connector always makes it work again.

What could be the exact culprit?

 

[CountMike]

Hello everyone, i have a Lenovo M72E workstation fitted into a custom case, that exhibits a really weird issue where the pc sometimes shows no signs of life after pressing the power button, and sometimes it works perfectly without a single problem.

It still has the same issue with a brand new good power supply, but i've discovered that when the pc is dead, taking it apart and replugging the 24 pin ATX connector always makes it work again.

What could be the exact culprit?

Some pin(s) on 24pin connector on MB ?

 

[alexborex]

Some pin(s) on 24pin connector on MB ?

Hmm, the connector is never touched during the time the pc works and breaks again..

 

[CountMike]

Hmm, the connector is never touched during the time the pc works and breaks again..

That doesn't mean it is not losing contact somewhere.

 

[alexborex]

That doesn't mean it is not losing contact somewhere.

I guess i'll try deepcleaning the contacts and see if it makes a difference.

 

[alexborex]

That doesn't mean it is not losing contact somewhere.

Update, i deepcleaned the board's underside and no change, it's doing the same

 

[helper800]

Hello everyone, i have a Lenovo M72E workstation fitted into a custom case, that exhibits a really weird issue where the pc sometimes shows no signs of life after pressing the power button, and sometimes it works perfectly without a single problem.

It still has the same issue with a brand new good power supply, but i've discovered that when the pc is dead, taking it apart and replugging the 24 pin ATX connector always makes it work again.

What could be the exact culprit?

If its not the 20+4 pin plug itself then i'd guess something happened to the motherboard itself. Have you tried resetting CMOS? BIOS update recently? Could have something to do with material contraction and expansion due to temps. Does it only ever have problems booting when its cold in the morning or hot in the afternoon?

 

[alexborex]

If its not the 20+4 pin plug itself then i'd guess something happened to the motherboard itself. Have you tried resetting CMOS? BIOS update recently? Could have something to do with material contraction and expansion due to temps. Does it only ever have problems booting when its cold in the morning or hot in the afternoon?

I reset the CMOS multiple times, and also updated bios to the latest version, yet it's the same.
It has issues booting any time of the day

 

[CountMike]

I reset the CMOS multiple times, and also updated bios to the latest version, yet it's the same.
It has issues booting any time of the day

I know that symptoms not suggest it but did you eliminate possibility of Start button or it's connection are not intermittent ?

 

[DaleH]

I know that symptoms not suggest it but did you eliminate possibility of Start button or it's connection are not intermittent ?

I agree with this post. One could test this with a DVM or by physically bypassing the switch with a small jumper cable. This is a good URL for understanding power supply operation and what occurs when the power button is pressed: https://www.smpspowersupply.com/connectors-pinouts.html

 

[alexborex]

I know that symptoms not suggest it but did you eliminate possibility of Start button or it's connection are not intermittent ?

In the past i remember i tried jumping the power pins on the motherboard with a screwdriver and still nothing (i also replaced the case's power button with a known good working one and it's still the same)
And i also set the bios's "last ac state" so the pc ALWAYS starts up when receiving power, and it doesn't.

 

[helper800]

In the past i remember i tried jumping the power pins on the motherboard with a screwdriver and still nothing (i also replaced the case's power button with a known good working one and it's still the same)
And i also set the bios's "last ac state" so the pc ALWAYS starts up when receiving power, and it doesn't.

Have you remounted the all of the major parts? Wonder if there is something that is intermittently causing a short. Maybe even a loose connector or spare screw.

 

[alexborex]

Have you remounted the all of the major parts? Wonder if there is something that is intermittently causing a short. Maybe even a loose connector or spare screw.

I did remount the motherboard into the case with no effect, and also blew the case with air and shook it to see if there are any loose pieces, and i found nothing (and also no change)
Also, one odd thing i should mention possibly related to some short somewhere, when i unscrew 1 screw from the power supply, sometimes the pc actually starts and works (although not consistently)

 

[helper800]

I did remount the motherboard into the case with no effect, and also blew the case with air and shook it to see if there are any loose pieces, and i found nothing (and also no change)
Also, one odd thing i should mention possibly related to some short somewhere, when i unscrew 1 screw from the power supply, sometimes the pc actually starts and works (although not consistently)

I would try unmounting the PSU from the case and test. Are you using standard length screws?

 

[alexborex]

I would try unmounting the PSU from the case and test. Are you using standard length screws?

Yes, it's using standard ATX screws