Member Avatar for johnhende

My desktop computer recently died on me. When I turn it on nothing shows up on the monitor. The fans and power are on (everything lights up at least) but there's nothing there. Then when I try to turn it off by holding the power button in it won't turn off. The only way to turn it off is to flip the power supply switch. Here's what I've tried so far:

- Made sure it's not the monitor by testing the monitor on my laptop (it's fine)

- Reset the mother board by re-seating the battery

- Tested with another power supply (same result)

- Rearranged the RAM (same result)

- Tried a new motherboard (same result)

- Removed drives and started the computer (same result)

- Switched out cpu with another cpu (same result)

- Tried to use a POST card (POST card didn't even show a message on it's LED)

So, that's where I'm at. Any help would be greatly appreciated!

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  • Latest Post Latest Post by Rik_

Dani AI

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Brief, targeted guidance to complement and without repeating component swaps already discussed.

Start with the front-panel and chassis. Disconnect the case power switch and use a small screwdriver to momentarily short the two power pins on the motherboard to turn the system on. If that gives normal control but the case switch does not, the switch or front-panel wiring is suspect. If the machine still only powers off when you kill the PSU, the problem shifts to the board's power-management circuitry or a persistent short to ground.

Do a true "bare minimum" bench test on a non-conductive surface: only motherboard, CPU (with cooler), one known-good RAM stick, PSU, and video (if required). Leave all USB, drives, front-panel headers, and expansion cards disconnected. Look closely for bulging or leaking capacitors, scorch marks, solder splashes, or bent/missing socket pins. A visible fault here is often the root cause when there is power but no POST activity.

Use a system speaker or attach one to the header to capture beep codes. If none are emitted, confirm the speaker is actually connected to the correct header and the speaker itself works. Verify the 4/8-pin CPU power connector is fully seated and check PSU rail voltages with a PSU tester or multimeter (only if comfortable and competent with mains-voltage work). Also re-check the POST card placement and compatibility; some cards need a specific PCI/PCIe slot and will show nothing if they are not seated or not supported by the board.

If these focused checks don’t reveal the issue, gather what you can (beep patterns or lack thereof, LED diagnostic indicators, PSU voltages, visible board damage) and report them. Those details will quickly narrow the fault to case wiring, PSU/voltage delivery, or motherboard-level failure.

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Member Avatar for Rik_

Are you using a graphics card or built in graphics? Does the motherboard have a system spaeker attached to it?

Member Avatar for johnhende

I have a Radeon 5770 that I use. I'm not aware of a system speaker on the motherboard.

Member Avatar for Rik_

So, it could possibly be the graphics card at fault then!

What motherboard have you got? I need it's make and model number, and do you have the manual that came with it?

Member Avatar for johnhende

It's a Gigabyte MA78GM-US2H and yes, I still have the manual. Also, I forgot to mention that I plugged the monitor into the motherboard graphics and the result was the same. So, I'm not sure it's the graphics card.

Member Avatar for Rik_

Ok, that's information you haven't given before. You say you tried another PSU and another motherboard but did you try the replacement motherboard WITH the replacement PSU? It's quite possible that one blew and took the other out!

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