Malfunctioning VT240 - help please

On 11 Jun 2020, at 15:14, Charles via cctalk <cctalk at classiccmp.org> wrote: ========= Thanks for the tip. I didn't see in the manuals that the keyboard light pattern was actually a binary code, but that makes sense! I would have expected an error message on the screen, but as I previously noted, the video system itself does not seem to be working properly. Unfortunately my logic analyzer is an ancient Tek 7D01, the equivalent of stone tools rather than metal ;) It's not really suited for doing this kind of work, but it's what I have... I wonder if anyone has already disassembled the code? The 4116's are soldered to the board, too. Since the memory map is shown in the tech manual I could write a simple memory test and burn an EPROM. My fear is that one of the PALs has altered itself from tin-whisker migration (fuse regrowth) :(