Question My display is going black!HELP REQUIRED

[Tuaha khalid]

I have a sff desktop Hp 800G1
Spec: i5 4570 ,8gb of ram , 1tb hard
I have connected an external gpu XFX RX480 8GB using an external power supply and pcie extention cable
Now the problem is when i start gaming all things work fine but suddenly after some time 20-30min later display turn black saying no signal going to power saving mode this same happens every time
I dont know whats the problem and which part is causing it

 

[Lutfij]

Mind sharing how you connected the GPU to your SFF system? Might also want to share the make and model of the PSU and the external GPU dock.

 

[Tuaha khalid]

i used an 420 watt INBOX ATX power supply and used an pcie extension cable 16x to 16x
I didn't used any dock except for the adaptor hdmi to vga to get display