International projectionist (Jan-Dec 1947)

New Selenium 6-Phase Unit Available Thru J. E. Robin A wholly new application of the underlying principles of one of the oldest rectifying substances known to science, and the direct outgrowth of intensive research and practical application during the war, is embodied in a new selenium rectifier now ready for distribution. To be known as the Robin Selenium Rectifier, this new unit will be distributed by J. E. Robin, Inc., of New York City. Selenium has a much higher reverse voltage rating, approximately four times that of other rectifier elements, states Emil A. Kern, president of J. E. Robin, who points out that this feature, where applied to requirements over six volts, requires fewer plates and has a greater safety factor. The use of a base plate of aluminum, continues Kern, materially reduces its weight, eliminates rusting, and facilitates radiation of heat. The selenium rectifier is held to suffer less from aging than other dry-plate types. During this period, the first 10,000 hours of operation, the forward and re verse resistances increase gradually, after which they become stabilized. Compensation of from only 5 to at most 10% is required in the a.c. input voltage. High Efficiency Rating Placing the efficiency of the selenium rectifier as 85% when new. to 80%, when completely aged, Kern points out that selenium units have been in use for 15 years and more without deterioration. No warmup period is required, it being ready for instant use, it does not deteriorate on standby and the efficiency is uniformly high over a wide range of load, having an almost 100% power factor. For 3-phase power lines this rectifier employs a transformer with a 3-phase primary and two sets of completely isolated secondary windings, cross-connected so as to deliver 6-phase power for fullwave rectification. Thus, the ripple frequency is calculated at 720 cycles per second. The unit employs a specially designed mica and glass insulated transformer with completely isolated low-voltage secondaries. Of the high-reactance type, this transformer acts as a ballast to mini Sneddon 6 KjreetinaS • * * PROJECTIONISTS LOCAL UNION NO. 407 I. A. T. S. E. SAN ANTONIO, TEXAS YOUR ASSURANCE OF THE BEST! WENZEL "Smooth-Running" PROJECTOR You Eire assured of "Smooth-Running" performance with the Wenzel timeproven projector. Use Wenzel's for precision replacement parts and your present equipment will do a smoother running job. WENZEL WG-12 Shock-Proof Gear Assures a maximum of shock absorfaance, the absence of warpage, and maximum resistance to oil deterioration. Write for our NEW complete catalog WC25. We will sell only through Independent Theatre Equipment Dealers. Mention the dealer serving you. HERE'S WHY THE IS UNEXCELLED / SEALED HERMETICALLY SIX ELEMENTS A true Anastigmat for pictures wiresharp to the very corners ... in blackand-white or color! SEALED HERMETICALLY No dust or oil can enter the SuperSnaplite ... it never needs to be taken apart for cleaning! ONE-PIECE MOUNT This sturdy all-aluminum one-piece mounting can't loosen up or leak oil! ANODIZED FINISH The gleaming gold finish of the SuperSnaplite is an integral part of the aluminum ... it can't chip or flake off! COATED OPTICS Durable anti-reflection coating on each glass-to-air optical surface nearly doubles the light transmission . . . gives brighter pictures, higher contrast! SPEED OF 1/1.9 Exceptional speed for the utmost in screen brilliance without extra current consumption! OTHER SNAPLITES The f/2.0 Snaplite Series II— hermetically sealed . . . critical definition . . . coated optics. For smaller theaters: the f/2.3 Snaplite Series I— coated optics optional. For complete details on all Snaplite lenses, get Bulletin 204 from your local supply dealer. 2 Franklin Ave. {^/fjflCa/ CORPORATION Brooklyn 11, N.Y. INTERNATIONAL PROJECTIONIST December 1947 37