Machlett Laboratories was a Northeastern United States-based company that manufactured X-ray and high-power vacuum tubes. Machlett was a large producer of the tubes and developed accessories to be used with them as well.
For its contributions to World War II efforts, the US government gave it an "E" award in 1945. The company was bought by Varian in 1989.
History
The company began as E. Machlett and Son, which was founded in 1897 in New York City, United States as scientific glass makers.
Early days
Machlett Laboratories was created from E. Machlett & Sons in order to exploit the then new technology of X-rays. They made X-ray tubes from the beginning to 1989 when they were bought by Varian. In addition to making X-ray tubes, they manufactured high-power vacuum tubes for use in radio and TV broadcasting (857B mercury-vapor half-wave rectifier tube) and for industrial induction heating. Those two sides of the business were about equivalent for most of the life of the company.
Machlett Laboratories, Inc. was established in 1934 on Hope Street and Camp Avenue Stamford, Connecticut. This manufacturing operation began making X-ray tubes and became the largest producer of its kind in the world. Raymond was president of the company, founded by his father Robert, a scientist who made the first practical X-ray tube in America and devoted his life to making it safe and successful in the field of medicine. Robert Machlett associated with Madame Curie and other leading roentgenologists to make this happen.
They moved to 1063 Hope St. in Stamford, Connecticut, in the early 20th century, and remained there. Among their achievements was a counter made by them for Irene and Frederic Joliot-Curie for use in their experiments on artificial radioactivity in 1934 which is currently contained in the Science Museum in Great Britain. They were given an “E” award by the US government in 1945 for their contribution to the war effort.
Products
Transmitting tubes
Machlett was well known for its rather complete line of transmitting tubes, most particularly triodes.
For quite a while, Machlett's 6697s were the most-used Class B modulator tubes (as a push-pull pair) and Class C final tubes (as a single-ended pair) in 50,000-watt plate-modulated AM transmitters.
In a classical Doherty amplifier (a Class B "carrier" tube and a Class C "peak" tube), 50,000 watts could be achieved using only two 6697s, but the drive requirement was about 5,000 watts, so the driver was often a complete 5,000-watt transmitter. The driver power could be "passed through" (i.e., was not dissipated as heat) if the carrier tube was operated with a grounded grid and, as before, the peak tube was operated with a grounded cathode.
Later, chief competitor Eimac released tetrodes which rather quickly eclipsed Machlett's triodes, as tetrodes have higher gain (thereby requiring much lower driver power, usually about 1,000 watts for 50,000 watts out), and do not require "neutralization". And tetrodes can be screen-grid modulated, especially in a Sainton-modified Doherty amplifier, where both the "carrier" and "peak" tubes may be operated in Class C.
6697s were also employed in RCA's upgraded Ampliphase transmitter, the BTA-50H.
CPI's Econco division remanufactures Eimac and Machlett power tubes.
X-ray tubes
They were the first company to utilize the concept of the rotating anode, something which is just about universal in medical X-ray systems at this date. Towards the end of the time of manufacture, they were producing oil-circulating X-ray tubes with a heat exchanger attached (for use with computed tomography (CT) scanners), with 5-inch diameter rotating anodes formed from tungsten-rhenium alloy and molybdenum, with a large mass of graphite attached to act as a heat sink. Smaller tubes without graphite heat sinks had highly radiative coatings to disperse the generated heat into the oil surrounding the tube itself.
The manufacture of X-ray tubes was licensed to two other companies, GEC Medical and Comet SA of Bern in Switzerland.