No video / help please.

Hello, my PC froze today, so I turned it off by holding the power button and when I tried to turn it back on - Boom - black. (Everything powers on, but ABSOLUTELY nothing appears on screen.)
I been planning on swapping my motherboard with another one I had, so I thought thats the right time to do it.
So I`ve changed the motherboard, It was working fine for a few minutes until I decided to plug in headphones, I got behind PC to plug them in and when I look back at the monitor - black again. (not sure if it happened as a result of moving PC a little or plugging headphones or just a coincidence.)
I know its not motherboard (hopefully), because other one did same thing.
CPU and Rams got changed together with the motherboard, so can`t be those either.
I tried:
Different GPU,
Clearing CMOS,
Disconnecting everything.

Anyone got any ideas what might be wrong, please?

Oh also a strange thing, I have connected a speaker to the pins, to see if it beeps or anything - no beeps, so I removed all ram sticks, because I knew its supposed to beep then 100%, no beeps anyway, even tried connecting different speaker - nothing.

There is only one slot for GPU in this motherboard, so I cant swap it into another one.

I tested PSU with multimeter and all the numbers looked good. (+- 0.02v).
I also tried using a monitor with DVI it says no signal, but when I use HDMI and connect it to my tv, hdmi cable lights up, and new hdmi source appears on tv.

It seems like I have tested everything, but it still doesnt work. My best guess would be is the PSU, but if it is how did I broke it? any tips on looking after PSU? because this one I only had for like 6 months.

Motherboard: ASUS M5A97
Previous: Asus Rampage Extreme II
PSU: INTEGRATOR 700W 80+Bronze

Thank you.

OK, cheers, I`ll get a new PSU then and no I did not, but I think theres no point, if new PSU wont help, I`ll have a look then.

Could you please help me choose a proper PSU then without spending a fortune? Last time I brought this, I checked for 80+ as I thought if it has 80+ on it its at least half-decent, but I guess not, ha. Thank you.

@DOUGIE , yeah thats what I thought, but I can`t remember where I put the receipt and the box, probably in the bin. (smart asf)
@phillpower2, I do realise that multimeter is not enough to fully test a PSU, I just listed things of what I tried so nobody offers me to try that or that lol. Thank you, though.
So any tips on choosing a proper PSU this time, please?

I found PSU proof of purchase (e-mails and ebuyer . com purchase history). You think that would be enough to return it for exchange or I must have an physical receipt and the box it came in? ty

Cheers, boys. My graphics card is MSI Gtx 960.
I still trying to turn it on sometimes, it does turn on and shows video sometimes (only happened few times out of loads, loads of tries over few days) and if it does shows video it beeps once. But then if I don’t press anything straight away it freezes. I did managed to get to uefi bios today, and it seemed like it froze, time did not change, so I left it on, cameback after some time, the clock time have changed, and the cpu temp bar was moving (not always, but every like 10 seconds or something) but I did not respond to any mouse movements or keyboard presses. My keyboard got custom color backlight (there is a button on it to change colors) - the button did work, my mouse got led`s aswell which were on, but the laser was off. (I guess its not getting enough power or something), actually same thing used to happen when it started crashing, mouse laser used to turn off and screen used to freeze sometimes, not always though. (The mouse and keyboard is working perfectly on another machine.) I also find out that (while I got into UEFI today) that when I plug mouse it the lasers flashes and then turns off and if I plug it in halfway, and apply little force up or down, it seems to stay on, though still couldn’t get any response on screen.
I have obviously tried different USB ports, and I think I should mention that previous motherboard used to do the same thing with mouse laser not working.

I`m quite busy with work and I live in a little village there arent any local Repair shops or anything and I dont really know anyone who could borrow me a PSU. :| Anyway, maybe the info above helps to identify if its really the PSU thats causing the issue, so I don`t buy wrong part. Any answers / suggestions are much appreciated.

While writing previous post, I remembered that few days before it happened for the first time, I been sorting old tangled cables out of my table, and I accidentally plugged a cut USB cable instead of my phone charger into front USB hub and + and - touched causing a sparkle which caused my mouse laser to turn off, but as soon as I saw it and plugged it out, my mouse went normal, so I completely forgot about that. As soon as I posted my previous message I went to disconnect my front USBs from the motherboard (To be more clear, these ports come with the case, so I thought that would make sense that even if almost all parts (except PSU) have been changed it is still happening, because it might be causing a short circuit or whatever its called in English.) After doing that, computer become starting more often / after less tries than it did before, maybe that is just a coincidence because it would still freeze (by freeze I mean, mouse / keyboard would stop responding and whatever is on the screen at the time would just stay on it like a picture, without anything moving / blinking / changing. Though now mouse laser would stay on anyway.)

I do have another PC with a PSU which doesn't not have enough pins to power up my Graphics card, so I realised if I power them both at once it might work. I know its probably not the best idea, not sure if its safe, but oh well, I plugged 24pin and CPU 12v cables from other PSU and the broken one left to power up the GPU, I connected green and black wires on 24pins cable for it to start, pressed the start button and Boom it works.

So now I know that the PSU is playing up. Anyway guys, do you think that USB cable`s positive and negative touching might have caused this to happen or its just a coincidence?
Also I can forget the refund for the power supply, if thats what caused it, innit?

Cheers.