PC won't boot into bios after working for years

[Maxim_6]

I have an issue. I'm fairly certain it's the psu. I've had this pc for couple years. Recently It's been taking multiple on/off cycles for pc to boot. Today it stopped booting completely. I connect the power, keyboard and monitor light up. I click the button. Psu, gpu, cpu fans spin, mobo lights up. I hear hard drive spinning(also have an ssd). Then nothing happens. Black screen on the monitor. I have tried replugging the psu connections, tried switching what disk it loads to, cleared cmos, tried starting without the gpu. I tried unplugging cpu power to get some sort of post beep, got nothing, but I think I need a special speaker? The mobo has no boot screen. This has been happening for couple weeks. Usually I retry starting and it boots but I think whatever the faulty hardware has finally died. I'm going to try my psu on a different computer tommorow. And a different psu on my computer. I was hoping may be there's some insight from these forums on this problem
It's Gigabyte z170 hd 3
Corsair cx 600m
Gtx 970
An i7, I'm not fairly certain which one atm.

 

[Paperdoc]

I can think of five possible areas that could cause this.
PSU failure
Mobo failure - the mobo has a section that controls all the voltages it uses
Video card failure (OR on-bpard video chip, whichever you use)
Monitor failure
Check connection cables between video output and monitor.