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Mechanical Television

Jenkins Radiovisor Model 302 - AWA Article

Richard Brewster's Television Column for April 2008

The Jenkins Television Corporation produced a number of mechanical TV receivers, both kit and factory manufactured. The model 302 was probably one of the last sets to come from the Jenkins Corporation in Jersey City, New Jersey.

The cabinet of the model 302 is 20 inches deep and high and about 15 inches wide.  It is a 60 line set utilizing a 12-inch disc with a spiral of 60 lenses of 1 cm. diameter and a newly developed crater tube. Ref. 3, page 423, notes that the new crater tube, developed by Jenkins, “…is a heavy duty type and operates on 30 to 60 milliamperes and will stand up to 100 M.A.”.  For a detailed explanation of crater operation, see the article by D.E Replogle, V.P of the Jenkins Television Corp (Ref. 1, page 338)

The projection assembly appears to be a model 100 ‘open’ set mounted inside the cabinet with the crater tube and spiral lens disc in place of the neon lamp and spiral hole disc!

The 60-line image is projected on a 7 1/2 inch square piece of ground glass mounted in a metal frame supported by two horizontal brass rods. Thus the viewing assembly can be slid out of the cabinet in order to focus the image. An intermediate convex lens, of approximately 6 inches diameter, is mounted 6 inches in front of lens disc. This lens is missing from my set.  On page 353 of Ref. 1, a similar set is shown, but apparently not incorporating this lens. 

Synchronizing is intended by means of the 60 Hz line power as in earlier Jenkins sets.  According Ref.2, Details Now Available for Practical Radiovision Reception, page 116, synchronism should be automatic if the receiver is on the same power system as the Jersey City transmitter. The article goes on to say that, “When operating on a different power system, the scanning disc can be readily kept in step by manual control, with little difficulty”. I’m not so sure about that!

Certainly, the resulting image should be one of the largest and brightest on a mechanical set!

This set was originally part of the Ken McIntosh Collection.

References
1. Television News, Nov.-Dec. 1931
2.  Citizens Radio Call Book, Mar. 1930
3.  Television News, Jan.-Feb. 1932