Oh, wow. I didn't realize it was that old of a technology. Thanks for that info and I stand corrected.
I know the split from the 4000 to the 4050 in formware and about DOS was fairly significant. I had started with HP LJ based out of Boise (we were field trainers and I was in PA) just as the 4050 was released. Of course, we were only forward trained, not so much backwards.
Thanks for the info. I have dealt with companies that still have a lot of old assembly line equipment that we always have to have spare 4000 and 4+ units. I knew it had something to do with the firmware/engine boards but didn't realize they were using pre-DOS.
Thank you all for your input. Refurbished 4050 N's are available on ebay for as little as $45. I believe my easiest, most economical option is to purchase an inexpensive refurb and put it in place of the defuct machine. My new M604 can be assigned other duties. Thanks, again.