Member postings for John Doe 2

One thing that might be a possibility is the computer power supply failing.

Some supplies are only just sufficient to provide the total current required by all the various devices, and as they age, they can reduce their output, and hence devices start failing. And/or if additional drives have been added, the PSU might not quite be coping; so when a drive attempts to spin up, it could drag the PSU voltage rail(s) down, and the computer might see this and assume a fault with that drive.

When you connected just the power lead to the DVD drive, the computer was OK probably because, without the data lead, the drive was not instructed to spin, so the current drawn was less than it would draw in normal use.

Another possibility is that although you checked the data wires for continuity and shorts, I am guessing you only did this with a DC multimeter? Of course, data wires now work at many megaHertz, and at these frequencies, certain electronic effects can prevent the data being 'cleanly' transmitted along them; for example capacitance between adjacent data cables - which would not show up with a normal multimeter.

Without sophisticated test gear, you are restricted to substituting cables and cleaning connections, as you have been doing.

I would (remove the wall plug), and go over the whole computer internally with a vacuum and a soft brush (very gently), to get any dust out of all the boards and open up the PSU to do the same. Dust can cause overheating and reduced current flow, (and in some cases, short circuits on circuit boards). I would also clean all the connections to the PSU and remake them a few times.

If you remove any items from the computer to clean them, make sure you wear an earthed earthing bracelet around your wrist before handling them - static build-up can kill some components.

Good luck !