when the shop said " broken gpu " did you rma that one and this is yet another one or is this the same gpu the shop said bad gpu , also thermal paste would of only possible helped if it was a overheating issue
the shop that diagnose my pc is the one saying gpu is broken. they tested with other gpu and my pc works fine. later i asked them to try with 750W which resulted with lesser black screen.
i cant rma there since i dont buy there. its a bit complicated and last time i rma something it takes about 3months to get the item back
i tried to google this issue, but it seems there are many ppl having the same issue, so im thinking this is a software problem rather than hardware for r9 290?