Vector Graphic Model SD-5031, aka Vector MT

I have the Vector Graphic machine listed in the subject line. It is a tan S-100 box with black panel, and a tan monitor that carries a logo plate that says "VECTOR MT". This Vector is equipped with a hard drive and a single DSDD 100tpi floppy disk drive. The hard drive controller (ST-506 interface) and the floppy drive controller (16 hard sector) are contained in the same S-100 card. The card etch dates it as 1980, and a silk screened note says it is a "FD & HD Controller". Despite considerable time spent with google and other search engines, I have been unable to locate any information of value about this machine. I have been using it quite successfully for some time. However, very recently, access to the floppy has become most erratic and the usual result is the error message "DRIVE NOT READY". However, on occasion it is possible to read the directory and read some of the files on an installed disk. I suspect that the cause of the problems are with the controller card, but without documentation I hardly know where to start any troubleshooting. So, to the point of all of this! If anyone has any documentation on this machine that they would be willing to share with me, please contact me either privately or publically. It will be highly appreciated!!! - don