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The CRT is a [[154-0642-00]] (<B080000) or [[154-0699-00]]. | The CRT is a [[154-0642-00]] (<B080000) or [[154-0699-00]]. | ||
==Background== | |||
Regarding his experience as a Tektronix manufacturing engineer for the CRTs for the Miniscope | |||
series (211, [[212]], [[213]], and [[214]]), Dale Dorando recalls: | |||
<blockquote> | |||
I worked under Bill Johnson, one of | |||
the manufacturing managers, especially the flood guns used in the storage CRT's. | |||
I was the weld lab manager too. We designed, tested, selected electrodes, and weld | |||
settings for the elements inside the CRT. | |||
<br> | |||
<br> | |||
The CRT division had a great concept where the new engineers work at each station | |||
for a week or two learning all the processes and actually making parts. The side | |||
advantage is you meet the production people and when you need something you know who | |||
to ask. | |||
<br> | |||
<br> | |||
The CRT's for the 211, 212, 213, and the storage version, 214, were manufactured | |||
using a pilot program where the same assembler worked on all phases of the tube. | |||
The other CRT's were being built by a person that only did one portion of the | |||
assembly. As an example, the deflection plates were assembled and carefully aligned, | |||
the next operator may not realize that and if accidentally bent, tried to bend them | |||
back. Naturally they wouldn't be properly aligned. By having the same people | |||
perform every process, they could see what was important and what could be improved. | |||
The primary goal was to find ways to improve the processes. By performing all | |||
the steps it was easier to find these improvements. The result was that with just | |||
these 4 operators. The yield and volume for the Miniscope CRT became much higher | |||
than the conventional CRT's. | |||
<br> | |||
<br> | |||
The cathode for the Miniscope CRT was a critical part of the design. It took | |||
several tries to get that right. It was being done in conjunction with our partner, | |||
Sony. Sony was to use the same 1/4 watt cathode in the Trinitron TV. | |||
The cathode was a direct heated type - the filament and cathode were on the same | |||
flat wire. This reduced the power necessary to heat the cathode to the required | |||
temperature. This was important for a battery operated device. The spacing | |||
between the cathode and the grid with extremely important for the intensity and spot | |||
size. If the filament deformed while being heated, the cathode could move. The | |||
filament had springs that kept it taught across a ceramic ring inside the grid cup. | |||
The cathode was a small disk with the triple carbonate coating blown on to the | |||
surface at a precise thickness. | |||
<br> | |||
<br> | |||
As with most of the Tektronix CRT's, it used deflection blanking where the beam is | |||
aimed off the screen during the horizontal retrace. This was faster and easier to | |||
control with the associated electronics than changing the negative high voltage with | |||
respect to the grid. | |||
<br> | |||
<br> | |||
Glass rods hold the elements in place inside the CRT. Having so many elements | |||
embedded in such a small glass rod made them fragile. The rodding process was | |||
carefully controlled for temperature and time. | |||
<br> | |||
<br> | |||
The bulb of the CRT was ceramic with an internal gold plating as the anode. The | |||
bulb was frit bonded at high temperatures to the glass neck. The faceplate was also | |||
frit bonded to the ceramic bulb. The faceplate was first silkscreened with the | |||
graticule. After the faceplate was bonded to the bulb, the phosphor was allowed to | |||
settle in a liquid onto the faceplate. The liquid was poured out and then aluminum | |||
pellets were evaporated on to the phosphor in a mild vacuum. The aluminum helped | |||
resist burning the phosphor and reflected the light from the back to the front for a | |||
brighter sweep. | |||
<br> | |||
<br> | |||
The electron gun was welded to the stem with the pins. That was inserted into the | |||
neck, that was previously bonded to the ceramic bulb, and using a lathe with a | |||
torch, melted the stem to the neck. The CRT was evacuated and the metals | |||
inductively heated to remove the gasses in the metal, then sealed. The getter was | |||
inductively flashed to a size dictated by a template for that CRT. The larger the | |||
flash, the better is absorbed the impurities, but too much flashing could short out | |||
metal parts. | |||
<br> | |||
<br> | |||
A coil was wound around the CRT to allow for a trace rotation adjustment in the | |||
oscilloscope. This would correct for any small gun rotational alignment. | |||
</blockquote> | |||
==Pictures== | ==Pictures== | ||