2 Jul
2007
2 Jul
'07
4:37 p.m.
From: "Rick Bensene" <rickb at
bensene.com>
Re: Getting Microcode off of Tape and Into Microcode Delay Line of Diehl
Combitron Calculator
---snip---
These machines were notorious for not "booting up" properly at power up
time. The tape would read, but the code that got loaded was incorrect,
resulting in a calculator that was catatonic, or sometimes did weird
things. The main cause of this was contaminants getting in the tape
reader optics. The tape reader was optical, with a light source on one
side of the tape, and two photodiodes on the other side. As mentioned,
the tape had two tracks, one a clock track, and the other a data track.
If dirt or dust, or oil from the mechanical printing mechanism got into
the optics, it would cause mis-reads, either clock pulses would get
missed (meaning missed bits in the microcode), or data bits would not be
read properly, again resulting in a bad microcode load. Keeping the
optics clean was a main maintenance point for these machines, along with
proper lubrication of the very mechanical print mechanism.
Hi
I found that the one I had would fail to boot for another reason.
Even cleanning the optics wasn't totally enough. I found that the metal
tape would not always pass smoothly through the reader. Some
times it would stick a little and then flash through the reader, faster
or slower then intended.
I found that I had to clean the surface of the metal tape as well
from any stray grease or corrosion.
I'd truly
love to have one today. I'm sure the one I used is long gone.
Keep up the good work. Many of the early electronic calculators were
truly great computing machines.
Dwight
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