Question Pc powers on with no output to monitor

[Brokencomputernvrright]

My pc completely shut off a while ago. Took to repair shop they said motherboard. I replaced the mother board. It powers on now but no image on monitor. Could it be the cpu or graphics card? When I took the computer apart, the thermal paste was almost all gone and not sure if you’re suppose to change thermal paste but it’s been around 3-4 since I built the pc. One of the pins on the heat sink fan is broken so it wasn’t complete held down tight enough maybe and fried the cpu? I put plenty of thermal paste. The heat sink fan turned on but that just means the mother board is working correct?
What I’ve tried so far:
-replace gpu wire from power supply.
- took out ram and put back in. Tried shifting slots too.
-tried using new hdmi wire, different monitors, dvi to hdmi wire.

Thinking of taking out the cpu and reinstalling? Not sure if that’ll do anything. Also will try taking the motherboard battery out and reinstalling.

Any suggestions would be greatly appreciated.

Comp specs:
Old crypto miner turns to pc.
-Rm850x psu
-Msi z270-A mb
-gigabyte GeForce gtx 1080 gpu
-intel core i7 7th gen cpu
-Corsair vengeance lpx 16gb x2 ram
-deep cool gammaxx S-40 cpu cooler

I have a spare gpu but not sure if it’s compatible or safe to use to see if it’s a graphics card issue? Listed below.
MSI GeForce GT 730 1GB GDDR5 PCI Express 2.0 x16 Low Profile Video Card N730K-1GD5LP/O

 

[punkncat]

Was the cooler broken when it was running, then quit? Did you have any indications just before that of issues with the build like lag, delay, other strange behavior?
I would suspect the paste was gone from the troubleshooting. Where it may dry cake and crack, it doesn't just "go away". Having a CPU run long term without proper cooling can certainly cause damage. Just FYI and tip for the future, a cooler costs WAY less than a CPU or even a motherboard.

I would not recommend spending a dime more towards fixing a 7th gen. Even a modern i3 would run circles around it and be compatible with W11 as well. Consider budget for a new machine using some of these parts.

 

[Brokencomputernvrright]

Was the cooler broken when it was running, then quit? Did you have any indications just before that of issues with the build like lag, delay, other strange behavior?
I would suspect the paste was gone from the troubleshooting. Where it may dry cake and crack, it doesn't just "go away". Having a CPU run long term without proper cooling can certainly cause damage. Just FYI and tip for the future, a cooler costs WAY less than a CPU or even a motherboard.

I would not recommend spending a dime more towards fixing a 7th gen. Even a modern i3 would run circles around it and be compatible with W11 as well. Consider budget for a new machine using some of these parts.

Ah will definitely consider a new one if it’s a cpu/gpu issue. I think when taking the clips out after it failed it broke.

There’s a task that I do regularly which started to cause delay/lag. I run screen recorded via obs and also run about 200 tabs of chrome. Obs would lag when I press start/stop. Then I’d have to close chrome entirely for windows to work. There are 2 monitors connected. One with hdmi the other with dvi to the gpu and dvi one stopped working so I assumed it was the wire which I purchased but by the time that arrived pc broke. It was a hot week weather week. I also never shut down the pc.