7 Dec
2010
7 Dec
'10
11:58 a.m.
On 2010 Dec 2, at 11:46 PM, Josh Dersch wrote:
I suspect the HP9100 is about the most common CRT-display calculator, at
least over here [1] but they're not all that common now.
[1] I've never seen any otehr CRT display model 'in the flesh'.
Got myself a Friden 1162 desktop calculator.
This is from about
1968-69 and has a neat-O keen CRT display and uses a
magnetorestrictive delay line memory. Kinda cool.
A very neat find, CRT-display calcs of that era are rare compared to
the Nixie-display models. Of all the calcs I have collected, I still
have yet to personally come across a CRT-display one. In my experience:
- you may get lucky and solve the problem in a general cleanup
and inspection of the machine,
- again with luck, a little bit of inspired tracing around
keyboard/operation start/terminate circuitry or timing circuitry
will find the problem,
- you'll need the schematic to track it down in depth,
If you can't obtain the manufacturer's schematic,
reverse-engineering is the option.
My own preference (from multiple experiences) is to do some cleanup and
inspection, and then go straight to reverse-engineering - a long
As is mine. Reverse engineering takes a lot of time [2] but you end up
really understnading the machine. And yoy _will_ be able to find the fault.
[2] Doing the HP9100B too me sevral months...
In general, the easiest things to revese-enginer are ones that contain
docuemtned LSI chips like microproessors. There is essentially just one
thing you can do with a microprocessor, so you've got identifyable
address and data buses, etc. Boards of SSI/MSI are harder -- an NAND gate
or ashift register could be used in lots of different ways. And discrete
transsitors are the hardest of the lot -- a transistor need not even be
used for a digital function.
Hveing reverse-enginered a number of devices over the years, I am happy
to provide hints if you want to have a go.
-tony