HP Forums

Full Version: HP75's schematics
You're currently viewing a stripped down version of our content. View the full version with proper formatting.

Have anyone the HP75's schematics?
Or where can I find them?

I'm examining the possibility to build some expansions (RAM and ROM) for my HP75D. So I need of documentation as much as possible (included the electrical schematics).


(as always delete the two "_nospam_" from e-mail address :-) )


There is an HP75C service manual, which includes schematics and bus timing data (for all 'service' meant board-swapping if you were HP). I am pretty sure this manual was available to the public at one point (it was mentioned in PPC journal), so there's probably somebody out there who has both the manual and a scanner.

Wow, it seem very interesting!

I hope that someone can post it to all the community!




I own a HP-75C...but what is inside?


I own a HP-75C...but what is inside?

A bunch of HP custom CMOS chips, including the microprocessor (a CMOS version of the HP-83/85/86/87 "Capricorn" microprocessor), ROMs, display drivers, bus drivers, keyboard controller, clock and alarm, card reader, HP-IL (1LB6 rather than 1LB3), etc. And some industry-standard 2K*8 SRAMs, HM6116 or equivalent.

Really haven't anyone them? :-((

I'm particularly interested to the expansion slots for the RAM and the ROM.



And inside of each of those custom IC's is... magic smoke. Once you let the smoke out of a package it quits working.

I have the HP75C service manual, what I don't have is any way to scan it :-(

Arghhhhh #@ยง!%$#&!#

I'm always unlucky!! ;-)