Jon wrote... I can do them with the Data I/O 29B and UniPak 2B. Some of the other UniPaks can handle them too. They are one of those devices that most of the newer commercial programmers can't do. I wouldn't call the Data I/O really affordable, though. ------ Same, I use a data i/o 29B for these. Jon is right, the 29B seems to have held significant value $-wise still on ebay. But you can find a reasonable deal once in a while.
And.... Watch out buying blanks on eBay, they're often pulls and are actually already programmed. Also the yield was not 100% even back in the day, apparently, so buy several to ensure you do get a good one. ------ I gave up trying to find any quantities of the 3 or 4 different bipolar proms used for the HP 2100/21MX line on ebay. I had significant luck contacting arcade game repair houses, and got a reasonable quantity of most all the flavors I needed. I checked back a couple years ago and all the usual arcade places no longer had them ☹ I do believe I saw a writeup on the web somewhere where someone took a different chip and programmed it to act like a (now) rare bipolar prom. I don't recall how successful it was - I'd imagine the speed of the bipolars would be an issue, plus ISTR height was an issue too (new chip was on a carrier of sorts, creating headroom issues on some systems). J
