HP 7470A plotter -- repairing/replacing paper feed rollers

On 4 Sep 2011 at 9:52, Philip Pemberton wrote: Is the 7470A anything like the 7440A in that different interfaces have different firmware capabilities? My recollection for the 7440A is that the RS232 and Centronics-interface versions have extra drawing primitives not present in the HPIB version. The 7440A has a warm spot in my heart. Back around 1985-6, I was working on a business plan and needed to run a series of charts. A friend volunteered his 7440A that he'd picked up at CDC's closing their retail business store. I had a copy of SuperCalc, which had 7440A support, but only the parallel and serial interface drivers. I remembered that Victor double-dutied the parallel port on the 9000 as both printer and HPIB interfaces, so I thought I'd make the IBM PC XT do likewise. It was a simple matter to convert a generic parallel card to bi-directional operation and I figured I could get away with its totem-pole drivers to drive a single device. So I wrote a TSR to hook BIOS interrupt 17H and translate the commands destined for a parallel plotter to the HPIB one. It worked like a charm and I was churning out color charts in no time at all. Fortunately, SuperCalc used only the basic drawing primitives and none of the extra stuff that wasn't present on the HPIB model. I think my code for this is still in SIMTEL --Chuck.