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What’s All This George A. Philbrick Stuff, Anyhow?

March 21, 2011
Bob Pease recalls conversations with George Philbrick in 1963 regarding analog control loops and switching supplies.

When I joined George A. Philbrick Researches in 1961, I did some technical writing for the R-300 power-supply family. Then I worked on some analog computer components and advanced vacuum-tube amplifiers like the SK2-V. Just as I was finishing off those projects, George Philbrick (founder and head of the company) grabbed me to work on some advanced technical stuff. I was designated as VP for Development, and I was cooking up lots of projects—and reporting directly to George. Silicon transistors were coming along, and I sure did start learning a lot. About this time, Tim Noble and Al Pearlman left Philbrick, so I worked on some hot amplifier projects. For example, see “Design of a Modern High-Performance Operational Amplifier” at www.philbrickarchive.org/1966-07_v14_no1&2_the_lightning_empiricist_01.htm (the P85A, p. 6) and “New Products” at www.philbrickarchive.org/1965-07_no1&2_the_lightning_empiricist.htm (the P25A, p. 2). I had a lot of fun, and wild challenges, for many years. George was not a simple person. He was often quite a visionary. But I got along with him well, and we had a weekly one-hour meeting on interesting learnings from the projects I was working on—and odd ideas. The Saw-Mill One day, about 1963, George told me about a sawmill he had invented several years previously—maybe 10 or 20. Unlike most sawmills, which run at a constant nominal speed but slow down a bit when you feed them a lot of logs and work, his sawmill would run at a barely fast idle. And when you fed it boards or logs or work, it would speed up to its best cutting speed. I had studied analog computers enough to know that, despite the problems of closing a loop around a lag, this loop was feasible. Specifically, if you put a little more flywheel on the saw blade, you could compensate for this lag, using a suitable differentiator (or lead) inserted in the control loop. This loading would be perfectly distinguishable from a similar amount of friction, and a loop could (in concept) do this just fine. Over the next four or five years, George mentioned this to me a couple more times. I agreed it would work well. In 2010, I started wondering what the other expert engineers at Philbrick remembered about it. I called up Dan Sheingold (apps manager) and Peter Hansen (manager of analog computation). What did they recall about George’s sawmill? To my great surprise, neither of them had any memory of GAP talking about it. Why did George challenge only me, and not the others? Well, I was the youngest kid engineer in the company. Maybe he was just testing me. But I didn’t get mad or confused. I knew he could make that sawmill, and I knew I could do it, too, using George’s standard analog computing techniques. But did GAP ever publish this concept? Did he ever demonstrate it? Or did he just talk about it to impress people? That is hard to say. None of us could figure that out. Maybe George just simulated this loop and proved its feasibility. Maybe. But I did realize that in the 1940s, the cost of energy (steam or gasoline) was pretty small, hardly worth saving a few seconds of the cost of energy between a fast idle versus a slow idle. I had done a lot of helping my father saw up old logs and branches. He never let me do any sawing, but I really did know a lot about sawing stuff. So George didn’t fool me at all. I also knew that a fast blade can blast through some small or medium-sized sticks, very quickly, and if you had to wait for the slow idle to come up to fast, just to cut a few small limbs, productivity would be hurt.
5-MHz Power?
Also at those weekly one-hour meetings, George told me how he wanted to improve the world by getting away from 60-Hz power and its heavy, bulky power transformers. He had done a lot of work with 5-MHz sines and square waves, so he was reasonably knowledgeable. Thus when he proposed that we all ought to do away with 60-Hz power transformers, I was impressed. He listed the advantages: it would be cheap, using small, cheap transformers; power filtering would be easy, etc. I immediately began to suspect that he was playing devil’s advocate. But I was not quite quick enough or strong enough to rebut him. I tried to figure out how he wanted me to reply. In retrospect, it’s pretty certain that he wanted me to rebut this proposal. First, the noise sprayed into the air would be excessive, and the local noise would be horrendous. Further, the power losses (by radiation or conduction) for 10 W, for a few meters of route, would be horrible—not to mention a mile. The whole scheme would clutter up the whole electromagnetic spectrum in the neighborhood just something awful. Again, George proposed this scheme to me three or four times, and I never balked or protested. Maybe I was reticent to criticize an old senior engineer who happened to be my boss. But I do think George was just testing me. Did George fool me? Probably. I’d love to tell you about George’s P7, but that will have to wait for another day.

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