PS3 not showing up on my tv

So my backwards compatible PS3 shows up on my TV with static
I was told to use the red white, and yellow cables instead of the HDMI
I did that and the video showed up for a few minutes, then the static came back
I changed the thermal paste because another video said to do that (some screws are now missing lmao)
And that didn’t fix it
Idk what to do
I just want wanna play fall and of cybertron😔