The Museum of HP Calculators
HP Forum Archive 06
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|Re: HP-33E Parts|
Message #1 Posted by Tony Duell (UK) on 12 Sept 2001, 7:43 p.m.
Sure no HP33E has battery backup, because as you said, it doesn't have continuous memory.
The point I was making is that the same keyboard 'PCB' (the flexible PCB wrapped round the metal plate with the keyboard on one side and the tracks to coneccted the logic chips on the other) is the same in the 33E and the 33C. And it's the same as the one in
every other Spice machine that I've worked on. The rearmost memory chip position (yes, the little 8 pin chips are the ROM/RAM memories) has its own power connection back to the PSU board.
In the 33E (no continuous memory), it's connected (in the PSU board/the flexiprint cable) to the same supply line as the other chips (not battery backed). In the 33C
(continuous memory), there's a few extra components on the PSU board to provide a battery-backed supply to this chip only (which is now, at least in part, a low-power RAM chip).
The memory devices (and CPU?) are different between the 33E and 33C, so don't think you can upgrade a 33E into a 33C by just swapping the PSU board -- you can't.
The interesting thing, though, if all Spice models use this same keyboard/logic 'PCB' is that HP must have thought about giving some models continuous memory from the very start, since they designed the PCB for it (the separate supply track).
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