5RP15 Oscilloscope Tube Teardown

En was looking around her grandparents' house on Sunday. It was also uncle Bill's house, but much of it was undisturbed from when his parents (En's grandparents) were still around.She brought home a bunch of way-cool-old ham gear and books and such. She surprised me with a big box."Well open it!"I opened the top flaps and pulled out a really, really big tube.I looked at the front and saw it was white:Oh. It's a CRT (Cathode Ray Tube). (No one guessed what it was at the house)It looked different than a TV CRT. For one it was round. This was obviously built more recently than the era of round TVs. Second, the form of it was all wrong. TV tubes are typically not as long. Then I saw the director plates.This sealed the deal.A TV doesn't have that type of beam director. A TV works with a set of big electromagnets (called a yoke) that slip over the back of the tube. The magnets push and pull the electron beam to cause it to scan back and forth and up and down to paint the picture on the screen. This works fine for something as slow and predictable as a television signal. Slow is relative -- the beam does scan very quickly, but the rate of scanning is quite constant. An electromagnet is, essentially, a large inductor -- it doesn't want to change its current very quickly. This is suitable for a TV.This is an oscilloscope tube! The directors are a matched set of electrostatic plates that move the electron beam around. The advantage is that these plates can change potential very quickly. However, this system can only change the beam's direction only slightly. This explains the length of the tube!A vacuum tube is a very simple system. A CRT is nothing more than a special case of a vacuum tube, albeit a bit more complex.No, I'm not really tearing it down... but it's a cool bit of kit to look at.From left to right:First you have the electron source, the focusing tube, the plate and the director plates.The source is nothing more than a heated filament or plate that has a negative potential. This is the cathode. (Hence: Cathode Ray Tube) This serves nothing but to "boil" electrons off its surface. The electrons, being negatively charged, fly towards the most positive plate, the accelerating anode.This is a view of the top (away from the cathode) portion of the accelerating anode. The electrons fly (at a great rate of speed) towards this plate. Between the cathode and the accelerating plate is the focusing tube. (left side of the above picture) This starts to form a nice beam of electrons instead of just a sea of electrons cascading to the plate.The electrons that are focused enough make it through the hole in the plate and hurtle through the director plates.From here it's relatively easy. Positive charge on plate attracts the negatively charged electrons as they fly by. Conversely a negative charge repels the electrons. This causes the beam to be deflected one way or another.Finally it hits the phosphor-lined screen. The excitation caused by the electron beam will make the screen glow in the familiar green color that we're all used to. (Ok, if you're old enough to remember green-screen displays)Of course the confusion could have been eliminated by reading the box.:-)I'm hunting for a pinout of this tube, but I'm not having any luck... I'm sure I can find the heater pins since those are connected... the rest would be trial and error and looking at where things might attach.It would be fun to play with though![smugmug url="http://photos.vec.com/hack/feed.mg?Type=gallery&Data=22035632_PPZKbk&format=rss200" imagecount="100" start="1" num="100" thumbsize="Th" link="lightbox" captions="false" sort="false" window="true" smugmug="true" size="L"]