Museum Hours:

Saturday 10-6

Sunday 12-5

 

Mechanical Television

Sanabria System

 

In 1931 the Western Television Corp. developed a theater projection system and demonstrated it around the country in 1933. The following is from Peter Yanczer:

 

Each and every demonstration of large screen television was attended thousands of people. Depending on the size of the room, the picture was either 6 1/2 feet or 10 feet square. The receiver equipment was generally placed on a eight foot high stand. The scanning disk was 45 inches in diameter and two inches thick. It was made of cast aluminum and has 45 three inch diameter lenses located in three sectors. It weighed 120 pounds and was put in place or removed using a block and tackle. On one occasion, after a show in Baltimore, the rope broke as the disk was about to be removed. It fell to the floor with a great crash and broke into pieces. Most of the 45 lenses were broken also. The disk was useless and had to be replaced. The next show was in 2 days, in New York and the replacement disk was in Chicago. Needless to say; for the next show, the equipment was ready. As they say, "the show must go on"!---and it did!

Some of the places where these demonstrations took place include: Macy's, New York,,, Abraham & Strauss, Brooklyn,,, Bamberger's Newark, New Jersey,,, Hoschild-Kohn & Co., Baltimore,,, Litt Bros., Philadelphia,,, Spear & Company, Pittsburg,,, Edwards & Sons, Schenectady,,, Sears Roebuck, Rochester,,, Pizitz, Burmingham, Alabama,,, May Company, Cleveland,,, O'Neil & Co., Akron, Ohio,,, R. H. Block, Indianapolis,,, Sears Roebuck, Chicago,,, Marshall Field Co., Chicago,,,Boston Store, Milwaukee,,, Golden Rule, St.Paul,,, Stix, Baer & Fuller, St. Louis,,, Crowley-Milner, Detroit,,, Poeple's Outfitting Co., Detroit,,, May Company, Los Angeles,,, Eporium, San Francisco,,, Meyer &Frank, Portland, Oregon,,, Brandels & Co., Omaha,,, Gimbles, Miwaukee, Easton's Stores, Canada,,, Garrick Theater, Chicago,,, The Century of Progress Exposition...

Other cities where demonstrations were given include:

Midland and Hamilton, Ontario,,, Medicine Hat, Alberta and Vancouver, British Columbia,,, Seattle, Washington, Des Moines, Holdridge and Lincoln, Nebraska,,,Witchita, Kansas. Nashville, Tennessee,,, Reading and Scranton, Pennsylvania,,, Providence, Rhode Island,,, Boston, Massachusetts,,, Cincinnati, Ohio.

As I recall, he had  a carbon dioxide filled crater arc lamp with a heated cathode, developed by a fellow named Taylor. I think this is the same Taylor that later started up his own transmitting tube manufacturing plant that was very popular in the 30s, 40s, 50s and beyond. Anyway, Taylor had a reputation for making very good tubes. I believe he designed and made some special tubes for Sanabria that were similar to the 845 who used about a dozen of them in the final output stage that drove the lamp. The lamp operated at about 40 volts at 1 ampere. (40 watts). I think I read somewhere the video driver could put out about 250 watts. The lamp was in an envelope similar to an early type #50 tube and somewhere I read that Sanabria had a habit of over-driving them and he burned out quite a few of the trying to get more brightness.

The rack on the right is the camera, obviously a flying spot scanner. On the left is his video amplifier. On the lower shelf you can see 6 tubes, which are the 845s. Behind them is a panel and behind that is another 6 of the 845s. I've seen his lens disk described as being  3 feet diameter and as  3 and a half feet diameter in size. Also, stated in this article is that the lenses were 2 inches in diameter. If that is correct, I believe the disk had to be larger than 3 feet. All things considered, a 3 foot disk would be too small.

Popular Science, October 1933

For more on this system see the February 1932 issue of Radio News and the November, 1931 issue of Everyday Science and Mechanics.

After the Western company closed its doors in 1933, Ulises Sanabria worked on a multichannel projection system. According to Bill Parker, an engineer with the company, there were multiple crater lamps, each illuminating a group of lines in the picture, resulting in a 120 or 150 line image on a screen up to 30 feet wide. The equipment was made by a company in Canada that built municipal water towers. The crater lamps were mounted on a copper strip.

The following is from a publication by Manuel A. Martinez, quoting a document written by U.A. Sanabria in 1966:

The development of my helium carbon dioxide arc for the television receiver started with low pressure light columns, using a hot cathode and a shielded anode with the shield having a copper tunnel in which the discharge took place.

After many trials we learned to conserve all of the discharge and work in a range of pressures which made the covering of the anode or the cathode with a sheath unnecessary.  A voltage drop of 65 volts across the cathode and anode went lower with a rise in current measuring 2-1/2 ohms negative resistance.  This made it possible to terminate a twisted pair of wires so that the positive resistance of the wire matched the negative resistance of the lamp.  Low loss at high frequency by the use of matching lamps and resistance made it possible to transmit over several miles of a twisted pair of wires with as good results as at the output of the transmitter.  We were, therefore, enabled to design a 10 channel mechanical system using only 15 lenses in a small disc which resolved a 10 spot lamp on a translucent screen.  This gave a total of 150 lines which had a resolution of 300 lines of present day television.

The system was ideal for wired television.  We only needed a disc, a synchronous motor and a lamp in the home. A 12 wire cable was used and no amplifying tubes were necessary in the home.  The synchronous motor was used to drive a recording hour meter so that the number of hours of television could be paid for like any other utility service. This system was very enchanting and was quite ready for commercialization in 1934.  It permitted the projection of 30' square pictures.

During tests, the screens were used out-of-doors and made of sand blasted celluloid reinforced by vertical piano wires.  The screen acted like a sail on a boat, so it had to be used with care.

A 1936 brochure from National Schools in Los Angeles has a diagram of a water cooled crater lamp, designed to be used in projection systems: