I've been strictly using dvd-rs not cd-rs for backups for the last two years now. I got tired of trying to relocate the various updates, system tools, and a ton of things along with various files like bmps, jpgs, wavs, etc. that were either found online or created on the system.
At this point the original drive is obviously too far gone probably due to the controller card there. While the platters were seen in good condition the controller card is what cooked. Did they try replacing that? They probably did since that is the electronic portion of the drive. Sounds like something is now shorted to ground. That could be in the harness easy enough if wires there were fused from the heat.