No Display showing - what could it be? (Other than GPU)

[dc1901]

Hi,
For a long while (many months) by PC had trouble booting up (sounded like fan would pulse over and over, then I would power off and on again and it would work no trouble) it then stopped turning on display at all and would only pulse fans like it didn't have the power to boot up (like pulling lawn mower chain over and over). I went in the computer and the GPU was very loud and I identified it as the problem. I bought a new graphics card and swapped out the old card for the new card. Also, I tried to clean/dust the other parts of the PC, refreshed paste for CPU to Motherboard, dusted PSU and general cleaning. I have added the new card but can't get any display on my monitor. Could I have done something to another component to stop the display from working?
Components:

Old GPU : Radeon R7770 Series
New GPU: Geforce GT 730 (I know this is downgrade)
Motherboard: Gigabyte GA78LMT
CPU: AMD FX 4100 QuadCore

I looked up if the graphics card would work with motherboard before purchase and it should work.
When I have turned on the PC with the new GPU there has been no sound or any sign of it working because it is low energy and has no fan to cool itself so I have no idea whether it is "on" and not working or not even on. I have plugged it in correctly because checked it many times. I have tried VGA output and DVI-C (which I got adaptor for).

Any reasons or help as to why I get no display would be appreciated.

THANK YOU

 

[Eximo]

Remove all components you don't need for troubleshooting.

CPU, Motherboard, one memory stick (try each one separately), the GPU, and the power supply. You can even unplug fans, for brief testing. Any device shorting out and causing a failure to start. Even unplug cables you aren't using. Including the front I/O (you can leave the power switch plugged in if you don't want to manually short the pins to start.

If it doesn't work at that point, you either need to look at the power supply or the CPU/Motherboard. If you haven't taken the opportunity to check the voltages on the powersupply, a decent multimeter can be had for as little as $15.
.
Now is a good time to ditch the old FX chip. Were I you I would return the GT730 and go out and get yourself a Ryzen 2200G and the fastest DDR4 you can afford.