How to debug an old motherboard that doesn't make beeps? I have an ASRock Z97 Pro4 with i5-4460 CPU. The problem is that the PC powers on (CPU gets hot, fans spin, HDDs spin), but nothing shows up on the monitor, the monitor doesn't even get a connection from the mobo. I tried disconnecting all components except CPU, CPU Fan, RAM, HDD without success.
When I power the machine on without a vital component like RAM, there are no beeps, so I can't understand where the problem is coming from.
I know the PC worked before, but I kept it in a box for about a year and my goal is to make it work again.
Edit: I've tried resetting the CMOS battery and checking if the mobo is connected to the PSU correctly, but nothing changed.