Oral History of Robert Everett - Computer History Museum
Oral History of Robert Everett - Computer History Museum
Oral History of Robert Everett - Computer History Museum
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Hendrie: How did they fix that?<br />
<strong>Oral</strong> <strong>History</strong> <strong>of</strong> <strong>Robert</strong> <strong>Everett</strong><br />
<strong>Everett</strong>: Well, they put their cathode together different ways, different – they were coated, the cathodes.<br />
They were metal cathodes with coats, proper coat on. You just changed the coat, and the material, the<br />
base material, and you could get something...<br />
Hendrie: You get it, yes; it was a material problem.<br />
<strong>Everett</strong>: It was a material problem.<br />
Hendrie: You needed to get fixed, and so you worked with the manufacturers <strong>of</strong> the tubes.<br />
<strong>Everett</strong>: That's right.<br />
Hendrie: Okay.<br />
<strong>Everett</strong>: And they made special tubes for us. They cost, I don't know, several dollars a piece as opposed<br />
to 30 cents or something. <br />
Hendrie: But they were worth it.<br />
<strong>Everett</strong>: Yes. And the other thing was the intermittent trailers. So, Jay invented marginal checking.<br />
Really what this was, if you had the field in which you're plotting voltages and repetition rates and things, if<br />
the spot you found where it would work all right was surrounded by a very narrow area <strong>of</strong> working so that<br />
as it drifted any way, it would drift into an area where it wouldn't function. First <strong>of</strong> all, you should design<br />
the thing to have as much space around it as possible. The second thing is that by changing usually the<br />
screen voltage, you could move the spot over, and you could find out whether you had enough space<br />
around it for it to work properly and to get rid <strong>of</strong> the tube if it started to drift over to one side when you – as<br />
you discovered that it was drifting too much out <strong>of</strong> the way. And you'd replace that tube before it failed.<br />
And this had a very, very positive effect. So, we had failure rates <strong>of</strong> vacuum tubes being measured in<br />
hundreds <strong>of</strong> thousands <strong>of</strong> hours.<br />
Hendrie: Okay. Through fixing the cathode problem and then do marginal checking, so you didn't get<br />
failures while operating. Good.<br />
<strong>Everett</strong>: Well, and just an endless number <strong>of</strong> things like that. We had to build our own test equipment, for<br />
instance. Nobody built test equipment for us. They had synchroscopes that were used for the radar<br />
business. They could be modified for looking at these pulse range and so on.<br />
CHM Ref: X3877.2007 © 2007 <strong>Computer</strong> <strong>History</strong> <strong>Museum</strong> Page 17 <strong>of</strong> 56
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