HP Forums
HP-71B HHP EPROM PCBs - Printable Version

+- HP Forums (https://www.hpmuseum.org/forum)
+-- Forum: HP Calculators (and very old HP Computers) (/forum-3.html)
+--- Forum: General Forum (/forum-4.html)
+--- Thread: HP-71B HHP EPROM PCBs (/thread-17581.html)

HP-71B HHP EPROM PCBs - HP-Collection - 10-14-2021 09:21 AM

I don't know if anyone has mentioned this here yet. There are at least 5 different versions of the HHP EPROM module for the HP-71B:

1986 version, silver contacts, resistor
1984 version, silver contacts
1984 version, gold contacts
???? version, silver contacts, resistor
???? version, silver contacts, jumper

By the way: I have lo lot of all differnet versions, PCBs and shells - if you are interested, please contact me.

RE: HP-71B HHP EPROM PCBs - J-F Garnier - 10-14-2021 12:25 PM

Basically, I only see two versions: the 1984 and 1986 versions.
The four lower units are basically the same, differing only by manufacturing details.
The part that looks like a resistor is actually an inductor (labelled as 'L01' on the 1986 version) for unknown use, maybe filtering. This inductor is present on all versions but can have several form factors, so the differences on various production batches depending on component sourcing.

Still I would be interested by the documentation of the HP interface chip (1LJ4), maybe will it be released someday thanks to the recent documentation effort.
I always though it could be possible to modify the 32K EPROM module to a 64K version, but would need that documentation.
32K is too small, with 64K it could be possible to put JPCROM + MATH, possibly plus ULIB52 (Forth ROM is not possible).