Did anyone on this list ever open the HP65 hybrid ?


Hi folks,

assuming that there are some defective HP65 out there,
where the fault location was in the hybrid, did you
ever try to open it ? I'd like to find how many chips
are inside and how they are interconnected. Maybe somebody
on this list could provide a photo (or a series of
photos). Sorry for this curiosity - but all of my attempts
to buy a truly defunct HP65 on Ebay have failed, all the
electronics were good, and I'm reluctant to kill a perfectly
functional HP65 main board just to see what's in the hybrid.



I haven't opened one, but I've seen an xray of it. IIRC it contains six chips. Based on the HP Journal article, these are most probably:

  • clock driver
  • C&T - control & timing
  • A&R - arithmetic & registers
  • CRC - card reader control
  • program storage circuit (100x6 dynamic shift register)
  • data RAM

Outside the hybrid are six additional chips:

  • three ROM chips
  • card reader analog chip
  • anode and cathode drivers for the display

Tony wrote an article on HP-65 internals which gives pinouts etc.

Half of the ROM source code was listed in two US patents. It may not have been the production release.

The operation of the program storage chip is partially described in the patent, but not in enough detail to write a simulation. A lot of experimentation would be necessary, probably by replacing ROM 0 with a ROM emulator and running custom test programs.

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