Re: HP41 Circuit Diagram Message #2 Posted by Tony Duell on 2 Aug 2001, 2:31 p.m., in response to message #1 by Vieira, Luiz C.
HP used higher density memory chips (both ROM and RAM) in later HP41s. That's essentially how they packed first the CV and then the CX into the same size case as the C.
At the logic board level, though, all boards have the same pinout (well, assuming they're not halfnut, since those machines don't have a separate logic board ;-)). You can swap them about without problems.
There is one caveat concerning the display driver, and a capacitor on the logic board (early display drivers need a different value), but if the display hybrid (at the top of the keyboard PCB) looks the same (the common one has 2 round black blobs of epoxy over the chips), then it'll be fine.
Later HP41 service manuals give half-a-dozen different versions of the logic board schematic using different types of ROM and RAM.
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