Question PC Black Screen. Can anyone help?

[InesrtNameHere]

I built a PC and all was going well for about a month. I had been playing a game for an hour or so and suddenly the screen went black. The PC still turns on and runs without power cycling but I have no picture at all.
Screen: Sony LED TV. HDMI input and cable have been checked and work fine.
PSU: Seasonic S12iii 650W. I tested the voltages: 24 pin, CPU connector and 2 x 6+2 pin connectors are all good.
Motherboard: ASRock B550M Steel Legend.
CPU: Ryzen 5 3600X with stock AMD cooler.
Graphics: iChill GTX 980 Ti
RAM: 2 x 8GB Crucial Ballistix - Windows Memory Diagnostic Tool found no errors.
SSD: 500GB Crucial P2 m.2
No BIOS settings were changed and no overclocking was done.

I borrowed a 100% working 1660 Super but I still get no picture.
The CPU doesn’t support onboard graphics but I can get a picture and boot to Windows if I use an "unknown" graphics card. Its a fake GTX 1060 so I’m not really sure what it is. In any case, it gets me a picture and confirms Windows boots.

I have a fair idea of what I'm doing but I'm not an expert in any of this.
Does anyone has any suggestions as to what might be going on here or what to test next?
Could it be the motherboard / PCIe slot? Maybe the lanes used by the fake card are still working but not the others?

 

[Koekieezz]

I built a PC and all was going well for about a month. I had been playing a game for an hour or so and suddenly the screen went black.
I thought I got a feint smell of burning but I can't be sure. The PC still turns on and runs without power cycling but I have no picture at all.
For a screen I'm using a Sony LED TV. The same HDMI has been checked with a PS4 plugged into the same TV input and it works.

The PC has a Seasonic S12iii 650W PSU. I tested the connections and the voltages at the pins on the 24 pin, CPU connector and 2 x 6+2 pin connectors are good.

The motherboard as an ASRock B550M Steel Legend.

The CPU is a Ryzen 5 3600X with stock AMD cooler.

My first suspect was the graphics card. I’m running an iChill GTX 980 Ti card using a HDMI cable.
I borrowed a 100% working 1660 Super but I still get no picture. The CPU doesn’t support onboard graphics.
However, I can get a picture and boot to Windows if I use an unknown graphics card. The card is unknown because it was supposed to be a GTX 1060 but it’s a fake so I’m not really sure what it is. In any case, it gets me a picture and confirms Windows boots.
I don't suspect the GTX 780 Ti to be the issue any more since the same problem exists with the 1660 S.

The RAM is 2 x 8GB Crucial Ballistix. I ran Windows Memory Diagnostic Tool and it found no RAM errors.

There is a 500GB Crucial P2 m.2 drive and no other drive at the minute. Since windows boots with the fake GPU, I don't suspect this to be the problem.

No BIOS settings were changed and no overclocking was done.

I have a fair idea of what I'm doing but I'm not an expert in any of this.
I was wondering if anyone has any suggestions as to what might be going on here or what to test next?
Could it be the motherboard / PCIe slot? Maybe the lanes used by the fake card are still working but not the others?

tl;dr the problem is the 980ti and 1660 super? and to be clear that it will display if it uses the fake 1060 or 780ti?

 

[InesrtNameHere]

The problem is not the video cards.
The 980Ti worked fine for about a month in this PC but now nothing.
The 980Ti and the 1660S both work in another PC.
Neither card works in my PC but I do get a 600x400 display output using a fake 1060 card

 

[Paperdoc]

I'm not familiar with all those cards. Just a thought, though: among the differences between the three cards is the way each gets POWER. Maybe? If the "fake 1060" card does NOT have the same power connectors as the other two, that could be a factor.

 

[InesrtNameHere]

Thanks for your replies.

All 3 cards use the same 6/8 pin VGA power connectors.
The 1660S uses 2 x 6 pins, the 980Ti uses an 8 and a 6 pin and the fake card uses a single 6 pin.
I tried both of VGA connectors and the fake 1060 card works fine with either one.
I also swapped the cables around in the other cards but it makes no difference.
The voltages of all the pins coming from the PSU are exactly what the manufacturer states in the spec sheet.