Restoring a HP9830B calculator.

[Tony Duell]

(05-23-2014 08:26 PM)MattisLind Wrote:  The only difference AFAIK between HP9830A and HP9830B is the memory board (second row left) and the memory address board (top left)

That would make sense. The 9830A uses the 1K*1 DRAMs (1103), the 9830B seems to use 4K*1 DRAM chips. Unlike the 9810/9820, the level converters (TTL <-> 16V PMOS) are on the RAM board in the 9830A, so the signals on the backplane are at TTL levels. So the memory data board (T register, as HP call it) uses TTL levels to talk to the memory.

Obviously the RAM board is going to be different between the -A and -B. The address decoder and RAM timing logic are on the memory address board, so that is likely to be different too.