21MX proms (per request)

Absolutely (assuming you count your engineering time as free), not to mention it feels rewarding to use clever engineering tricks to solve a problem instead of money. But I want to keep my machine original and vintage if I reasonably can. My programmer ended up very reasonably priced, and it is recognized as one of the better vintage programmers of that era. So it fits perfectly in my collection of higher end, historically meaningful engineering tools. Two birds with one stone, so it was a pretty easy decision. Marc around $3-400 which IMO is a little steep for a 30+ year >old PROM programmer. Hopefully your best offer successfully accepted was much lower! 29B, you could design a replacement for the original >PROM, have some boards fabricated, stuff them and you'd still be ahead a few hundred bucks ...