Neon Logic

http://www.computerhistory.org/events/lectures/johnniac_09151998/johnniac_x… Well, that bell rang frequently. Finally, we had to convince Harriet -- by the way, this lady worked graveyard shift, midnight to eight in the morning -- to stay over a little extra, and we would meet with her, and find out what was going on. We asked Harriet to please go through, in gory detail, exactly what had happened when the payroll failed. By the way, she couldn?t give me the data, or anybody else, because Harriet Pierson, besides top management, was the only [person] allowed to look at payroll data, so -- it was worse than top secret. It was compartmented like you don?t want to know. Anyway, Harriet stayed over, and came in, and went through this exercise, and for the exercise she had created dummy data, just in case we might look at it. Well, nothing failed, and she couldn?t believe it. So we said, "Tell us exactly what you did." So we backed up, and she went through the whole thing, and I said, "Just go back out into the machine room like you normally would, after you loaded the machine." And she did. The first thing she did is, she walked by the door, is turn the lights off. But the drapes were open, and there was lots of light in the room, and so it didn?t have any effect as far as we could tell. But, when we sat down and thought about all this, we said, "Gee, maybe you?d better simulate the whole situation." So we closed the drapes, and ran the payroll program. And sure enough, after about 15 or 20 cards, we got an echo check error. The damn machine was afraid of the dark. Open the drapes [laughter], turn the lights on, and the machine ran fine! [Laughter] Makes no sense. Until Dick Stahl, one of the technicians on the machine, remembered that the neons were an active part of the circuit, and apparently by running a little test he determined that without any sunlight coming through in the windows, or fluorescent light from the overheads, which provided just enough ionization to keep them active, they deionized to the point where they would no longer conduct. [Laughter] Now, the question was, how do we fix this? There were something like two hundred and some odd -- how many neons were there? Well over 200. And nobody wanted to get in there and unsolder and resolder 200 -- the machine would have been down for a week at that point. Then somebody had a brilliant idea. Down here, where the air ducts for the return air from the air conditioner were, they put a bank of fluorescent lights on each side of the machine. If the filaments were on, they were on, the machine never had to run in the dark again. It never did. [Laughter] It never was afraid of the dark again.