https://youtu.be/UKcC-gDt6Qo
One HP 51604A ink cartridge. Three machines from three companies, built 42 years apart. I run the same pen through all of them, on camera, back to back.
The Diconix
A Kodak Diconix 150 Plus portable printer — the exact model this pen originally shipped in — gets unboxed, serviced, and printing again, dealer sales kit and all. This is the machine I did my homework on.
The Canon
A new-old-stock Canon BP-1200DH printing calculator runs its first tape ever, straight out of the box, 40 years after it was built.
The Reiner
A Reiner speed-i-Jet 798, a handheld stamper made in Germany and still sold today, proves the engine never actually left. Same cartridge, current production.
One Pen, Three Machines
Then one 51604A cartridge goes through all three, one after another, to prove the case Part 1 only argued on paper. If you haven’t watched Part 1 yet, it builds the wider case — Scantron, banks, fax machines, military printers — before this one puts it on the bench: The Most Used Hidden Printer in the World Graded Your Tests (Part 1).
Rob streams live repairs and builds every Tuesday and Saturday at 7pm Eastern on Twitch. His current series is Shelf Life — pulling broken hardware off a ten-year shelf and not stopping until he knows why it died.