April 1959 Popular Electronics
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Usually when you think about vacuum tubes, you envision the
short type that plugged into your parent's TV set or radio.
While they were sophisticated in their own way and also required
careful assembly with a lot of manual operations, these high
power tubes were in a class of their own. Even the one in this
article from the April 1959 Popular Electronics is not as complicated
as some of the ones designed and built for high power radar
As always, it is interesting to note the lack of eye protection
during assembly operations, especially given that the glass
could easily shatter at any point. I'm guessing that the guy
in Figure 1, doing the glass shaping operation over a hot flame,
only has on glasses because he happens to need them to see (i.e.,
Popular Electronics visits a tube manufacturer while...
A Transmitting Tube is Born
Photos by Joe Petroveo
The manufacture of a high-power transmitting tube involves
more than just assembling a number of metal and glass parts.
In order to meet the demands of industry, the manufacturer must
pay ever-increasing attention to reliability and long life.
The manufacturing processes which most affect tube life are
those relating to the precision with which the electrodes are
manufactured and assembled, the extent to which all impurities
and foreign particles have been eliminated, and the degree of
vacuum obtained inside the tube.
Recently POPULAR ELECTRONICS visited the Amperex Electronics
Corporation plant in Hicksville, N. Y., to find out how a manufacturer
of high-quality electron tubes handles the problem of building
long life and reliability into a modern high-power, high-quality
transmitting tube. A typical transmitting tube, the 5924A, was
followed through the different stages of its manufacture, and
photographs of each of the key steps were taken.
1. Glass technology is an important aspect
of tube manufacturing. The glass is softened by jets of flame
from a specially designed fixture. When the glass is soft enough,
the operator shapes it with special glass-shaping tools.
2. Cleanliness is more than a byword to the
tube manufacturer. Tube life and reliability are decreased when
impurities, such as oxides, are deep within the metal elements.
Here the electrodes are placed in a hydrogen atmosphere furnace
to "reduce" oxides.
3. The cleaning process goes on. The most
modern and efficient cleaning equipment is used by Amperex at
various stages of tube manufacture. Here an ultrasonic cleaner
eliminates the last vestiges of surface contamination which
may exist on the tube's metal electrodes or glass parts.
4. The care exercised in fabricating and cleaning all the tube
components naturally extends to the inspection procedures. Parts
are projected many times their actual size on a screen so that
even the slightest degree of misalignment is easily detectable.
5. Having insured the cleanliness and accuracy
of all components of the tube, the assembly procedure begins.
The first step is to assemble the delicate filament structure
with hand tools.
6. The metal anode is now mounted. In background,
note the different stages of assembly of the 5924A tube. The
assembler always keeps the working area immaculately clean.
7. Anode is sealed to the grid and cathode
mount. A highly skilled operator performs this exacting procedure
on a lathe-like machine which was designed for this operation.
8. Creating the vacuum inside a tube involves
more than just pumping out gas. It also includes removing gas
trapped within the tube elements. To do this. the electrodes
are heated until the impurities are driven off. Here the gas
is pumped out (through the horseshoe-shaped glass tubing) while
the tube elements are heated.
9. After all gases and impurities are pumped
out of the tube, it is necessary to make certain no other impurities
enter. This is done by "sealing off" the opening through which
the gas was evacuated. A 5868 tube is shown here.
10. Now for the finishing touches. With the
same care exercised in the internal fabrication and assembly,
all the external surfaces are carefully silver plated and, at
the same time, specific areas are painted for purposes of identification
of tube elements.
11. The final step is to "fire it up" and
subject it to a thorough testing. All electrical characteristics
are tested to insure that the tube will not only meet, but exceed,
Posted October 7, 2011