No POST on an old machine. Worked 2 days ago

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Hello,

I have a ~4 yr desktop that recently stopped POSTing (fans spinning but nothing on the screen). The last thing I did before the problem started was to reboot to install a Windows update. Since then, I have gotten it to POST 2-3 times after clearing CMOS, but it never booted because it forced me to enter BIOS and then stopped POSTing after I saved settings.

Any advice on what to do next to get it running?


Specs:
Motherboard: Asus P8Z77M-Pro
Ram: 2x8gb Corsair DDR3 1600 Mhz
Cpu: Intel i7-3770
PSU: Kingwin Lazer LZP-550 (550W)
GPU: AMD R9 280

Troubleshooting steps so far:
Clearing the CMOS and replacing the CMOS battery with a fresh one

I have tried running with the GPU card installed and without.

Running with 1 RAM stick. Tried each stick in 2 slots.

Checked PSU connections to the motherboard

I have also I installed an mini-speaker to hear beep codes. Usually I hear nothing. Once or twice I got 1 short beep which according to the manual means: VGA detected, Quick boot set to disabled, No keyboard detected.

I read through the No POST sticky, but most of it seems to apply to new builds which this is not. I don't have a multimeter meter or spare PSU to test with.

 

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Update: after powering on and off the computer about 20-30 times the machine will POST and then I can boot to Windows. However, every time I reboot I have to go through the process of powering on and off a whole lot to get it to work. Any ideas on what's wrong?

 

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Update: I ended up fixing the problem by reflashing the bios using the USB Bios Flash built into the motherboard. Not sure why that fixed it, but I haven't had an issue since.