Question HP Z400 Red Light PSU Issue

Jul 21, 2022
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I have a HP Z400 with the following specs:

CPU: Intel Xeon X5550 2.67 GHz
Motherboard: Hewlett-Peckard 0B4Ch

RAM: 8 GB RAM DDR3 @ 533MHz (dual channel)

GPU: Nvidia GeForce GTX 750 Ti Windforce Gigabyte 2 GB VRAM

Power Supply: Stock HP Z400 Power Supply 475W

Now a little bit of background. A few days ago there was an explosion in my area probably related to electricity as there was also a power outage. My PC was on and due to the outage it shut down. There was burning smell afterwards and probably a spark or two I saw.

After electricity was restored my PC was no longer booting up. The power supply seemed dead as the motherboard light wasn’t on either. I bought a used (probably refurbished) HP Z400 power supply with the same power rating as the old one. It worked well for one whole day. The next day I tried booting up my PC I was met with the red light blinking 4 times with a beep each time. Official HP site states it is a power failure issue. The motherboard light is on when I plug in the PC and if I press the power button the CPU Fan and GPU fan turn on briefly for a second before they stop and the red light appears on the power button beeping/blinking 4 times.

Yesterday while fiddling around the PSU wires (mainly P1 24-pin connector) to the motherboard my PC finally booted up. I turned it off and after trying to turn it back up was met with the same red light issue.

Things I have tried so far:
Unplugging all devices
Unplugging all PSU connectors except to the motherboard
Fiddling around the wires.

Is the PSU completely dead or just has a faulty/loose connection to the motherboard? Do I have to get it replaced?
 
I've come across this problem a couple times with HP computers, very typical HP PSU thing. Standard resolution is by unplugging the PSU and holding down the power button for about 15 seconds. After that, let go of the power button for about 5 seconds after and then normally pressing it once should boot the computer up as usual. That's always fixed my problems so far.

HP states this on their website: https://support.hp.com/us-en/document/ish_1997210-1528385-16
 
Jul 21, 2022
3
0
10
0
I've come across this problem a couple times with HP computers, very typical HP PSU thing. Standard resolution is by unplugging the PSU and holding down the power button for about 15 seconds. After that, let go of the power button for about 5 seconds after and then normally pressing it once should boot the computer up as usual. That's always fixed my problems so far.

HP states this on their website: https://support.hp.com/us-en/document/ish_1997210-1528385-16
I tried it twice now and it did not work. The red light issue appeared again. Also something to note is that my PSU fans also do not start spinning..

EDIT: I removed all RAM sticks except for one and then held the power button even when the red light was beeping and apparently the PC booted up.. I then added each RAM stick one by one and now have all added with the PC booting up.

EDIT 2: Restarting the PC brought the issue back.
 
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