Why won't my PS3 spin up a disc even after I replaced the disc drive?

A little while ago I purchased a used PS3 Super Slim (CECH-4301C) from ShopGoodWill. I probably should have fully tested it first before tearing it apart and cleaning it, but after I put it back together, I started it up and everything seemed to work fine until I put in a disc. The disc drive would not spin up the disc at all.

I then took off the cover and pushed the switch that the cover would press when it was closed to see how the disc drive would respond, and I saw that the laser head would move a little, but there was no laser shining and beyond the little movement it wouldn't do anything else.

At first I assumed the problem was the ribbon cable going from the laser head to the motherboard because it was a pretty badly wrinkled, so I found a replacement from a seller on eBay and bought it. I switched it out with the new ribbon cable and turned it on, but when I did, a small amount of smoke came from the laser head. I quickly turned it off then switched the ribbon cable back to the old one to check if everything was fine. Thankfully it was, but obviously the disc drive still didn't work. So I put the new ribbon cable back in and this time when I attempted to start the PS3 it would start for a few seconds then automatically shut off.

I contacted the eBay seller to talk about it and he said that the issue was that the disc drive is shorted somewhere. The motor that moves the laser head is independent of it, and therefore that works fine, but it's shorting in the laser head somewhere and therefore won't spin up the disk at all and the reason why its turning off the PS3

So I bought a new disc drive, the exact same one that comes in the PS3 (KEM-495 AAA) and I put it into the PS3 yesterday, but it still won't spin up a disc. The motor moves the laser head, but the laser won't shine either. So I'm back to square one. The PS3 won't spin up a disc despite me putting in a disc drive that is fully tested and working.

Any idea what the issue could be? At this point, I'm thinking it could be the connector where the ribbon cable connects to the motherboard, or it could be an issue on the motherboard, but everything else works fine, so I don't know how that could be the issue. Any thoughts would be appreciated.