IBM 5285

Hi All Another recent addition to my growing collection is, as the title suggests, an IBM 5285. It has a 12" display and dual 8" floppy drives. The separate keyboard is connected at the front of the machine by a large 25 pin connector. Originally passed to me as "working" the machine fired up to display what looked like a single ASCII code at the top centre of the screen and a column of blocks on the far right. The keyboard is laid out very much like a terminal keyboard and testing the keys the keyboard buffer quickly becomes full. This results in what looks like a series of memory addresses along the bottom of the screen. All the while the two 8" drives are merrily spinning away. I have one disk with the machine which when inserted in either drive fails to read or alter the state of the display. My initial thoughts were faulty connections. I took the covers off to reveal about a kilo of dust liberally spread around the inside. I cleaned each component carefully and replaced the boards. Now I don't get anything on the display and the drives still whirr around oblivious of disk or no disk... So... my questions are: 1. Has anyone come across this model before and is it a dumb terminal? 2. What checks would you suggest to solve the disk access problems? 3. Can anyone point me towards a repository of information about it? Thanks in advance Alan