PSC QuickScan GP5385-104342 RS-232 / DOESN'T WORK!

I think the problem you all are having is that this model of scanner requires a "decoder" to work correctly. It is another box which goes in-line between the scanner and the RS-232 port or ps/2 port of the pc. I'm not 100% positive about this, but I am pretty sure this is the problem. You need to look on e-bay for a psc barcode decoder.

No that scanner doesn't need any power supply, it's problem is on your cable, i suggest you to bring it to the nearest authorized service center, or you could unscrew some bolts that attached to your scanner, and find the trouble by checking the cable one by one using AVO meter your self.