HP-45 With Shielding?

[Steve Simpkin]

(03-22-2020 05:53 PM)JohnRausch Wrote:  Here is a comparison of the circuit boards. The one from the calculator with the shielding is on the left, one from 1350A 37499 is on the right,

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Very interesting that the one on the right has a mix of Mostek and AMI ICs as well as the 16 pin 1820-1128 clock/reset IC that replaced the 0855 and reduced the discrete parts count.

From Electronic, Feb 1973 regarding mixing of the two manufacturers for early production of the HP-35:
"Production models are either all-AMI or all-Mostek because the two suppliers' chips don't really run well together. Though the parts are the same electrically, the different locations of the precharge make it impossible for the Mostek A&R to operate with the AMI ROMs."
https://www.hpmuseum.org/forum/thread-3746.html

IC part numbers:
http://www.brouhaha.com/~eric/hpcalc/chips/