got an HP 9915A computer

The HP9915 is very similar (elecrornically) to the HP85,. but in a metal case that can be fittied into a rackmount kit. The 3 edge connectors at the abck take the mormal HP85 interfacs, there's are pins on the main PCB insde that act like a built-in ROM Drawer and take HP85 ROMs. There's also an internal PCB that can take EPROMs, and which I believe can be used as a read-only mass storage decice, Tye BNC conenctor on the back is standard TV-rate composite video. The DB25 socket is for a keyboard. That keeyboard is rare (read next-to-impossible to find). But it's just a matrix of swtiches. There are pinouts (and schematics) for the 9915 on the web, the keyboard matrix is the same as the HP85 matrix, and I think the official service manual for that is on the web too. The frontpanel buttons are electically the programamble funciton keys on the keyrboard, and the shift key. -tony