3 ms·

The Xerox Alto works great sitting in a nice air conditioned Silicon Valley office. Put one in a steel mill with motors and welders wreaking havoc on the electr

• theamk 9mo ago
  Well yeah, 7400 needs clean power, so you need to have a good power supply. And if you are in a steel mill, you probably add an extra input capacitor or ten, few chokes, and even shield the whole thing. This is somewhat complex, but not impossible. After all, even the worst "super fast runt pulse" won't survive a simple L-C filter, as long as the filter is done correctly (say with bulkhead-type capacitor and metal shielding). Why then author's company failed to do this? I don't know.. Maybe they didn't have anyone with the right kind of knowledge, maybe they were cash strapped and weren't ready to pay for huge metal boxes and hundreds of EMI filters. (The latter does actually sound plausible - after all the engineer was fired for messing up a single revision of 12"x12" board.. and a good oscilloscope that can see the high-frequency pulses is much much more expensive that such board.) An example is somewhat famous AN/UGC-74 terminal, which is built on 5400 series (a higher cost version of 7400). I could not find a lot of good pictures, but there are some at [0]. Note: - Electronics are in many individual sealed metal boxes - One separate shielded section just for input power filtering - Dozens of power supply filtering capacitors (small black squares, the "cpu board" seems to have ~1 per chip) - Weights 100 pounds from all that metal, and not cheap! I bet that one would work in the steel mill just fine. [0] http://www.vintagevolts.com/the-an-ugc-74/ http://www.vintagevolts.com/the-an-ugc-74/