We repair a classic HP 3478A 5-½ digit voltmeter, and admire its ultra complicated A to D converter. HP Multislope II ADC patent: https://patents.google.com/patent/US4357600A/en Ian Scott Johnston video on HP 3457 backlight mod: https://www.youtube.com/watch?v=oEu7nqOkKxo Blacklight display mod: https://www.eevblog.com/forum/testgear/another-hp3478a-backlight-display-hack/ LCD protocol reverse engineering: https://www.eevblog.com/forum/projects/led-display-for-hp-3457a-multimeter-i-did-it-)/msg1347268/#msg1347268 OLED mod: https://www.eevblog.com/forum/testgear/hp3548-hp3457-oled-display/ Ken Shirriff's Nanoprocessor reverse engineering: http://www.righto.com/2020/09/hp-nanoprocessor-part-ii-reverse.html Ken Shirriff’s reverse engineering of the hybrid in Marco Reps’ HP 3458: https://x.com/kenshirriff/status/1448392567167479812?s=61&t=UXfboHQEfahjAKeGVe1J8w Jeff Peletz amazing HP instrument pictures: http://hparchive.com/wallpaper Stuff that supports the channel: - Amazon links for the tools I use in the lab: https://www.curiousmarc.com/amazon-links - Channel merch on Fourthwall: null - Legacy channel merch on Teespring (I don't have everything transferred to Fourthwall yet): https://teespring.com/stores/curiousmarcs-store - Support us on Patreon: https://www.patreon.com/curiousmarc "Elevator Music" Credit: Crinoline Dreams by Kevin MacLeod Our lovely sponsors - PCBWay: fast turn PCBs, https://www.pcbway.com/ - Electro-Rent: https://www.electrorent.com/ - Keysight: test instruments: https://www.keysight.com/ - Samtec: connectors: https://www.samtec.com/ - R&D Microwaves: https://rdmicrowaves.com/ Get more technical info on the companion site: https://www.curiousmarc.com/ Contact info: null