Tried no.1 even worse, monitor doesnt even turn on.
No.2 tried but still the same.
Go into bios first, check if your onboard graphic is enabled.
You will need to remove your existing graphic card after that incase of conflict/confusion.
otherwise I think you get blackscreen because the output is only at the graphic card.
Please correct me if I am wrong. But im quite sure this is the case(encountered this before)
As other posts suggested, eliminate other possibilities by cleaning your ram contacts either via isopropyl alcohol or eraser(with alcohol being more effective).
instructions:
Use a lint-free cloth, put some alcohol on it, then clean the contacts. Let it dry for awhile, then replace back.
You can use tissue but make sure you don't leave any debris behind as tissue can leave small particles.