HD1957AEL

Learning and Planning Ahead Mechanic Learns about Electronics

My training had been as an airplane mechanic and mechanical engineer; with prior experience as a Civil Engr (materials testing and surveying for bridge and road construction), Process Engr (tooling for aircraft-& automotive); thus I found myself in a completely new element as Lead Engineer at the Bombshelter test lab. It was essential that I learn something about electronics. It was embarrassing to not understand the vernacular or names of parts. Some of the engineers were taking classes at night on topics like “Controls Systems Synthesis” where they learned the new mathematical methods applicable to servo controls. The company seemed to have an abundance of those fellows. I was daily confronted with how to deal with the hardware devices they brought to be tested, and build systems, that could be operated remotely, to test them – some tests were hazardous. They were using names and terms I didn’t understand. I began the learning process by reading parts catalogs and studying the wiring diagrams for hobby kits – they didn’t teach what I needed to know in colleges or night classes. I sent for catalogs, pamphlets, parts & kits – I learned by reading and doing – there was a wealth of material available for the person who looked for it.

Fig 6.1-1 Diode radio Fig 6.1-2 Transistor superhetrodyne radio right.

During the Navaho program, I built a “crystal” radio from a schematic in a Sylvania booklet advertising their new semi-conductor diodes. It had five parts: tuning capacitor, fixed capacitor, diode, antenna wire and ear phones. I fit the three “radio” parts inside a Skippy Peanut Jar. It worked great for the LA basin where there were powerful radios like KFI beaming down from Mt Wilson. The circuit diagram for this is shown in the next figure.

I next built an all transistor radio from a Miller Coil diagram. It would not work after my first attempt, I was very discouraged -- and very busy – I put it aside. A couple years later, determined not to let it defeat me. I took the coils apart – the windings did not match the diagram! I corrected my wiring to match the way the coils were wound and it worked! The quality was lousy, by then I knew how it should have been built to suppress noise and I moved on. It had served it’s purpose, tenacity had refreshed my confidence. I emulated how IBM had made their computer cards, by drilling holes in formica sheets, bending the wires and soldering them. Printed circuits evolved from these and similar methods. The diagram for this is shown in the next figure

Upper left of Figure to the right shows the parts and diagram of the circuits inside the Skippy peanut jar. This is now in the museum at Oberlin KS.

I modified a later version that included one transistor by adding a second by direct coupling NPN and PNP transistors. I connected that to a small speaker with enhanced home made sound box. I used that as a Garage Radio for many years. Leaving the parts exposed for neibor kits to see. That too is in the Oberlin KS museum.

The bottom right diagram is the Intermediate Frequency transformer coupled full up radio of the kind later built and sold in large quantities, usually Japanese made.

Fig 6.1-3 All Transistor Hi-Fi with base, treble and volume control for both channels

There is no printed diagram of how this was made as it was all done from sketches on scratch paper.

When Bob Kelley joined us, at the very beginning of Minuteman, several of the fellows were assembling vacuum tube Hi-Fi Systems from kits, usually Heath or Knight kits. Bob said, why don’t you build a Hi-Fi using all transistors? I asked, what’s the advantage. Bob said you don’t need transformers especially those in the output amplifiers – transformers are the greatest source of Hi-Fi noise. He said his friends, at the radio transmitters on top of Mt Willson, who beam broadcasts down over LA, pay close attention to their output amplifiers. Their amplifiers use very large transformers to achieve quality. From this beginning I proceeded to build my own all transistor hi-fi amplifier, now in the Museum at Oberlin KS.

Fig 6.1-4 Included selector for Tuner, Tape, & Photo inputs – using very early transistors

Stages aligned using square wave generator & oscilloscope

The center boards are the same but flipped so the large capacitors could poke through the others circuit board.

From these experiments and Bob’s teaching I was to learn much about square wave. Bob said it requires a high quality amplifier to create the sharp corners of a square wave – the corners are the equivalent of very high frequencies. Bob recommended that I use square ware to establish the bias resistors for the amplifier stages of my hi-fi – replicating the square wave is much more demanding. Selecting the bias resistors is how you align signals to the linear range of the transistor. I adjusted transistor biasing this way for each stage, often having to go back and adjust a prior stage. When finished it indeed produced high fidelity – and I’d learned how to shield to block out noise. These home experiments proved very helpful at work.

This was ahead of it’s time, HiFi enthusiasts were still assembling Heath Kit Vacuum Tube sets and had not entered the world of transistors. Motorola & Delco of GM had just come up with the “door knob” power transistors as output stages for automotive radios. These Germainum Transistors were some of the first on the commercial market. The small signal transistors used were early devices made available to hobbiest, those used had double digit numbers – within two years many companies were making transistors and identifying numbers went up. The biggest drawback was finding good “large capacity Capacitors in small envelopes. I was using some I bought from the salvage yard and salvage from experimental board – in fact many of the small parts such as variable resistors came from such boards. It was a very interesting and rapidly changing time. I would over and over use things & principles I learned from these experiments on other applications.

Above black and white photos were originally taken in color on top of the following tables shown in color. Many of the parts shown here are now in the Oberlin KS Museum

Photos of some parts were taken on top of these tables made of 3/8x1x3 inch pieces glues together edge to edge from center out with assembled edge sanded before next piece was added. All wood pieces were from bushes and tree clippings from our yard. This was done while learning digital electronic.

Preparing for B-70 and Supersonic Transport Testing

(Emulating a Transformer to Isolate Hot and Cold)

Fig 6.2-1 Capacitor coupled Amplifiers

Fig 6.2-2 Transformer coupled Amplifiers

While the Minuteman program was consuming more and more of Flight Controls attention, we were still working on aircraft systems, primarily in support of the LA Aircraft division. Bob McCoy was the aircraft projects engineer, with Jim Passwater an assistant project engineer, and Jim Anderson the lead design engineer. Jim had done the experimental designs for some of the B-70 servos, which were used on the flight vehicles, and Jim was also working on the F-108 proposal. Most people believed that there would be follow on work on a Supersonic Transport.

There was also research efforts going on headed by Fritz Gardner, with Harry Horowitz, RE Smith and Jim Jewel doing design work. Attention at that time had been on developing a “digital” servo valve, or “digital servo actuator”. Conventional wisdom was, now that transistors permitted building digital electronics, there would be a need for “digital” components.

Several years later, after Minuteman III, I shifted to doing studies on how to replace analog servo controls electronics with digital. At that time I came up with a way to adapt digital electronics to the analog servo valves and analog positions transducers. At the time of early Minuteman this did not seem possible and much work was done by Autonetics and others to develop digital hydraulic components.

Vacuum Tube Radio; early transistor radios used same architecture

Transistors 1956 style: Upper left options on how to connect a transistor, lower left how to bias a transistor, Upper right package types, lower right heat sink methods for power transistor. These kinds were used to make HiFi amplifier in prior photo and radio below.

Bob Kelly, a remarkably capable engineer.

I owed much to Bob Kelly. I’d gone to Odel Taylor, supervisor of MM I Flight Control Electronics, to obtain an Electronic Engineer to build electronics for us to use in testing the Minuteman parts. He assigned, in fact transferred Bob Kelley to Paris Stafford my boss who assigned Bob to work with me in the Bomb shelter test lab. Bob did not have an engineering degree and Odel wanted to retain his “best” to do the design work using the then new transistors. Bob Kelley was an early day Ham Operator who learned radio by building his own transmitter. Bob had used glass plates from a green house to make a high voltage capacitor so they could communicate with Europe from his home in Massachusetts. In time I noticed that the engineers with degrees, working for Odel, were consulting with to Kelley to determine how he’d managed to build his Minuteman servo control loop electronics. I watched and listened as Kelley demonstrate what he’d done showing outputs on an oscilloscope. They were all having a problem with noise generated by the 6 khz square wave used to excite the position transducers. Batteries were Minuteman’s only a source of electrical power, thus it was necessary to chop DC to make “AC” to excite the linear Inductive Transformers used as position transducers. This “noise” penetrated the otherwise clean analog signals from servo valve amplifiers -- the retained engineers were baffled on how to solve this. I listened as Bob demonstrated and told them that high frequency noise only looked bad on a scope, that servo valves were unable to respond to such frequencies, that the noise source was known and balanced, it was simply averaged by the valve torque motors – the valves operated on current noise only detectable to with instruments as high frequency voltage spikes. I would later make use of this principle when using digital chips as servo valve drivers. Bob was very capable and much appreciated by persons like me. Bob died about 1970.)

Electronic Kits: This experimentation was essential to my learning how to perform remote control and instrumentation. I used Allied Radio parts catalogs to learn the names of parts and sent for kits to build at home to understand how things worked. Electronics engineers spoke to me as if I understood, it was embarrassing not knowing the names of common electronic parts. This hands on learning was very helpful. Transistors were new and I applied them to simple devices.

For example I used a phono crystal and amplifier from home built phonograph setup I’d made for my kids to remotely measure vibration of a high speed drive out in a test cell. It worked surprisingly well.

To align and test my all transistor hi-fi amplifier system it was necessary to build kits as Vacuum Tube Voltmeters, Signal Generators and Oscilloscopes to generate square wave signals and fine tune amplification stage biasing. Bob Kelley sketched how to make a transistor HiFi speaker driver without a need for conventional very large transformers used for vacuum tube HiFi systems. That all transistor Sterio Hi Fi Amplifier, shown above, was used as the family HiFi system in our living room while out kids grew up. It’s now on display at the Oberlin KS museum.