I had a very traumatic close call with my Tek 555 in 1973 which I used during graduate school. This was in the large multimillion dollar budget Princeton Plasma Physics laboratory where I was working on nuclear fusion. The problem was that I was setting up for an experiment -- which often took several days. This 'very small', 40 foot long 10 foot diameter electron plasma generating machine was not turned on. It had an approximately 4 to 6 k Gauss magnetic field when fully operational. When I say small, it was small compared to the Tokamak!! The Tokamak required a power generating station, roughly equivalent in size needed for city of Princeton.

I remember setting up for my experiment, and setting up the 555 scope near an electron probe which entered the plasma machine within a resonant cavity. Triggering was often difficult (pre-tunnel diodes in the 21, and 22 time base circuits), so it often took a lot of work to set the equipment up and make sure it would not move during activation of the magnetic field.

The problem was that I was standing up next to the 555 cart adjusting the triggering, turning on gigahertz RF oscillators to drive a resonant cavity, and while I was spending some time during this, the dual beam moved up to the right, my watch started to come off, and the 150 pound scope -- cart and all -- started to move toward the magnet. I suddenly realized that someone had turned on the magnetic field without checking to see if anyone was in the room -- I yelled to whoever was to turn off the magnetic field and I jumped back just as the scope jumped up into the air, and hit the side of the machine. The scope narrowly missed crushing me by a fraction of an inch... I did tell my wife back in 1973, but somehow she did not realize how close a call it was.

After I calmed down, I remember the scope was demolished, but I wasn't!! In those days the laboratory had a very large Tektronix section with at least a dozen scopes in repair. I had not gone down to the repair shop before, but since I came so close to my meeting my maker, I decided to take a look at my scope in intensive care! The beauty of the internal construction and pressed me to this day.. So now I like restoring Tek scopes.

As I recall it took at least a month for that original TEK 555 scope to be repaired!! I 'borrowed' an unused 555 from another lab within the military complex to finish my experimental work. Needless to say that caused some commotion, but it was not actually theft since it was still in within the military complex. Eventually someone gave me another 555, and I completed my graduate work.

Now as of last year I began restoring a different Tek 555, which is in this room! Both the beams are working, but only one distributed vertical amplifier has been restored to operation. That took six months using a full color Tek 555, 21A, 22A service manual. The tunnel diodes are working! My remaining problem is an undocumented resistance/capacitor ceramic wiring assembly containing 1.05 k and 2.5 k resistances that supply the lower distributed amplifier power. The upper one works fine, with 300 V on the distributed amplifier side. But the lower one has only 200 volts, with a non-working distributed amplifier, and some very hot resistors, not listed in the manual.

Jim Flick, PhD Princeton Astrophysics 1975.