My old pc was running fine until it suddenly turned off

Question

Custom Built Desktop PC

A Desktop PC built from off-the-shelf DIY parts, rather than a prebuilt from a major manufacturer. These can also be built by an SI using off-the-shelf parts.

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Vagelis @vagelis48076

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crwdns2931729:0crwdne2931729:0: Kho 24, 2023

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My old pc was running fine until it suddenly turned off

Hi I have an old computer

Today I turned it on and it worked fine for ten minutes until I opened YouTube on a browser and right about when it was ready to load the computer suddenly turned off.The pc wasn't turning on again.I changed the power supply and the pc turned on but the pc turned on when I pressed the power supply's button(Which is strange because It should turn on when I Press the power button on the case).The pc did turn on but there was no output to the display,the fans were all running, the hdd and CD drives were not running and when I turned the pc on the motherboard speaker (Which usually makes a bip sound when i turn the pc on)the was no bip sound.Also as you can see in the video in the front io were the led lights are the red is always on while the green is blinking very fast.In conclusion I found out that the power supply is broken.If anyone knows what else could have been broken please respond.

The videos link is here--> https://1drv.ms/v/s!Ak-yh_hDI_zVggPLb_15...

Edit: found out that the psu died and took the motherboard with it.

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Hi @vagelis48076,

What is the make and model number of the motherboard?

What do the red LED and green LED normally mean, Power HDD etc?

crwdns2934271:0Kho 25, 2023crwdnd2934271:0 jayeff crwdne2934271:0

@jayeff

My motherboard is a Gigabyte p4 titan series GA8IE800

For the lights I am not sure but I think green is the power and I think it supposed to stay always on , while the red led I think when the hard drive is doing something like opening a program etc. It stars blinking.

crwdns2934271:0Kho 25, 2023crwdnd2934271:0 Vagelis crwdne2934271:0

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crwdns2933315:03crwdne2933315:0

Hi @vagelis48076,

What is the make and model number of the motherboard?

What do the red LED and green LED normally mean, Power HDD etc? — jayeff
@jayeff

My motherboard is a Gigabyte p4 titan series GA8IE800

For the lights I am not sure but I think green is the power and I think it supposed to stay always on , while the red led I think when the hard drive is doing something like opening a program etc. It stars blinking. — Vagelis

Quilla @quilla crwdns2934065:0crwdne2934065:0: 1 1 · Answer 1 · 2025-08-05T10:34:20-07:00

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Quilla @quilla

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crwdns2931729:0crwdne2931729:0: masiku 2 agoMha 5, 2025

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One time, the PSU went bad and messed up the motherboard. The fans and lights would turn on, but there was no screen or beeps. I tried changing the RAM and re-seating the CPU, but it didn’t help. Once, it was just a dead CMOS battery, but other times it was a bigger issue, like something on the motherboard was fried. If the PC turns on right when you flip the PSU switch, that’s usually a bad sign.

If you end up wanting to rebuild on a tight budget using older parts, I’ve had luck using CPUs like the Xeon E5-2680 v4 with cheap LGA 2011-3 boards. Performance was decent for daily stuff and older games, and troubleshooting felt a lot easier on those platforms.

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Thanks for the response. I finally became knowledgeable enough to find out that the psu essentially burned the motherboard.

crwdns2934271:0masiku 2 agoMha 5, 2025crwdnd2934271:0 Vagelis crwdne2934271:0

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score 0 · Answer 2 · 2023-06-25T06:11:33-07:00

jayeff @jayeff

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crwdns2931729:0crwdne2931729:0: Kho 25, 2023

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Hi @vagelis48076

Some things to try and to check:

You said that you changed the PSU, just verifying that you connected a +12V 4 wire cable from the PSU to the socket next to the CPU? - see 3) ATX_12V ( +12V Power Connector) on p.17 of the user manual. This needs to be connected so the PC can boot

Try a power refresh and check if that works - see 18) BATTERY (Battery) on p.24 of the manual.

Perform a paperclip test on the new PSU just to make sure that it is alright.

Try disconnecting the HDD and check if you can start the PC and get into BIOS with a display. If you can, what OS is installed on the HDD, WinXP, Vista, 7, 8.1, 10?

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i have tried everything and the pc starts up but doesnt display anything and the green light flashes.Also when i turn on the power supply the pc imediatly turns on without pressing the power button.Also i have an old pc that has the same motherboard and the same problem it just doesnt want to output anything on the display.

crwdns2934271:0Kho 19, 2024crwdnd2934271:0 Vagelis crwdne2934271:0

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score 0 · Answer 3 · 2025-08-05T16:55:19-07:00

To turn on the PC, the power button causes a transistor on the MB to short the orange wire to the green wire.

If it turns on automatically, then either the power switch/wire is shorted or the transistor is shorted.

Not displaying anything can be a multitude of problems - and possibly what cause the transistor failure.

Disconnect the main power connector and turn on PSU. check for 12V on the connector. if none, it isn't in the PSU cause it isn't coming on.

Check for a short between orange and green wires.

Check the power switch and wiring for operation.

That should find why it is powering on.

Then reassemble. When it boots, do you get a POST beep (assuming you have a speaker connected)?

Is there any sign that the computer is actually booting up - check disk activity LED.

Check the voltages when everything is plugged up. Do you have 5V and 12V where it is suppose to be.

Is it integrated or a PCB graphics system? If everything above checks out, it is likely a hardware issue.

Try another monitor. If all that fails = you can't check drivers, cause you can't see anything. If the system isn't booting, it doesn't make much sense to try a different graphics board.

I would then remove RAM and any PCBs and see if you get post beeps. If not, your CPU is likely dead.

Custom Built Desktop PC

My old pc was running fine until it suddenly turned off

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