HP 41C Video interface test. Howto?

[Garth Wilson]

What happens if you select the HP-IL device number and output something to it, for example if it's the second device, do 2 SELECT OUTA (with something in ALPHA to show)? That's the simplest way I can think of that should display something. Make sure the devices on the interface loop are connected and turned on when you turn the 41 on so it finds a completed loop and initializes it.

(07-09-2020 06:23 AM)tribidouille Wrote:  The circuits at this time were big and human-repairable. Would it be possible to replace the ram or any other part, you think?

The first thing I might suspect is if there's an EPROM whose data has faded and it needs to be re-programmed. If someone else has the same model and an EPROM programmer, perhaps they could read theirs out and either send you the file or offer to refresh yours or program a new one. I have the HP92198 80-column video interface and I've refreshed the EPROMs a couple of times over the decades to make sure they don't lose the data. I kept copies of the files so I don't need to read valid EPROMs to be able to program them again. I believe one has the program material and one has the data for generating the characters, which interestingly gives the option of programming in different ones, like if you wanted them to match what the common Epson dot-matrix impact printers that were ubiquitous used, which is the DOS/ANSI character set.