HP-45 versions


Hi! I was wondering if anyone out there could tell me how you differentiate HP-45 versions? Only thing I can find are sites that mention the sort-of timer functions on early ones built. Thanks for anyone's help!!

Edited: 13 June 2005, 7:34 a.m.


AFAIK, very early HP-45 had a small stainless steel strip near the power switch. Later ones only had silver galvanized plastic there that wears off and then looks ugly. Inner values also do differ: my oldest one (mid 1973) has completely golden galvanized keyboard contact strips, LED module pins and PCB traces. It also has a 8-pin clock driver and the reset circuit is discrete transistors. My later ones have less gold (neither in keyboard, LED nor on the PCB) and a combined 16-pin clock driver/reset chip. As for the stopwatch, all those in my possession have the same HP part numbers on their microcode ROMs (1818-0057 and 1818-0082, including one made in spring 1975, so I guess the hidden stopwatch should be there in all HP45s built between the 33th week of 1973 and the 20th week of 1975 (date code of oldest chip in the machine).


Thank you for your info!!!


I also noticed when opening them that my earlier (with the metal strip and 3D ON-OFF) model has a metal screen around the top of the calculator (for EM regulations?) while the later one doesn't.



Minor nit: the term "galvanize" very specifically means "to coat with zinc". Silver paint on plastic, or gold coated contacts, are not "galvanized".


Very early models reversed the order of the opeands in stuff like "STO - reg" and "STO / reg".

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