No video output from my rig

[pk0312]

I bought an older MoBo (http://www.gigabyte.com/Motherboard/GA-965P-DS3-rev-33#sp) and two Radeons R9 290 and am trying to set it up but I can't see anything on screen. When I turn on the rig (shorting PWR pins), I can see a change on screen (a label showing "1080p/50Hz") so I guess there is some communication. I've used HDMI cable from graphic card to screen.

The motherboard should be working but it does not have an integrated graphics card so I was forced to use one of the Radeons. At first, I put it directly into PCIEx16, and connected it to PSU (1x8 + 1x6 pin). Powered on, no video output. Then I connected it via riser using one of the PCIE x1 ports on MoBo and made sure to power the riser from PSU with a molex connector. Still no video output.

At this point I have connected the bare minimum: CPU(was already on when bought), RAM (2x 1GB DDR2, was already on when bought). I only added GPU. And MoBo was working before in a computer. SSD was connected but its completely fresh.

How do I start troubleshooting this?

Here are photos:
https://i.imgur.com/QoydfPi.jpg
https://i.imgur.com/YeFuK4j.jpg

Edit:
After a while I got this garbage on screen:
https://i.imgur.com/27fwGq4.jpg

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[boatznhoes]

try resetting the cmos

[xxcsu]

You might going to be in  trouble mining with 2x 512Mb DDR2 ram .

Are you using a TV as a monitor ? Are you sure the TV supporting the Screen resolution / Frequency what is the output of your vga cards ?

"How do I start troubleshooting this?"
Try connecting to a computer monitor . Did you installed any driver for your cards ? or just plugged in the card and connected to the TV ?

Edit:
After a while I got this garbage on screen:

That garbage on the tv screen might mean your tv can not handle the signal from your vga card . Im building computers for years , built a lot of HTPC for special requests. This happened with me a few times in the beginning when i tried to set up the HTPC with a tv . After i connected a monitor , installed the right drivers , and then connected the HTPC to the the TV , problem always resolved .

[pk0312]

Actually it's 2GB RAM, made a mistake earlier. Now the thing is that I was sure TV should support HDMI out of the box. I have another monitor, but it's VGA and I don't have the converters (DVI/HDMI->VGA).. I am not sure what you mean by "installing drivers" as I can't see anything. So converters might be next thing to try and get. But it's really strange that 1080p wouldn't be enough.

[xxcsu]

"I am not sure what you mean by "installing drivers" as I can't see anything"

That was my guess , so there is no drivers installed at all for your vga cards . And you connecting that vga card to the TV  . So the first troubleshooting advice from me , is try to get a monitor and install the vga drivers on your system . Im not 100% sure im right with this or not , but i would start with this ....

I think without the proper driver installed , the "HDMI handshake" function not working between the tv and the vga card.
If the "handshake" doesn't work, the HDCP encryption that is embedded in the HDMI signal is not being recognized properly by one, or more, of the connected components. This most often results in not being able to see anything on a TV screen.