NAEB Engineering Newsletter (Dec 1958)

First, there’s no physical difference between the Model I and the I-Prime. The I-Prime is 3 db bet¬ ter at 7000 cycles, has 30% less distortion and gives better definition on the sound track. If your Model I galvo needs repair, an overhaul will cost you $120 plus parts or it can be converted to the Model I- Prime for $300. One reason for the modification of the mounting platform is to permit the use of an F- Prime (variable area) galvo. Since its snout is shorter, .270 inches of the shoulder of the platform must be milled off to permit proper focus on the film. At the same time this milling operation is per¬ formed, Maurer representatives would like to see the method of mounting the galvo changed. They have machined the bottom of the galvo assembly and threaded it to permit it to be fastened by two screws from below. They feel that it is desirable to have the galvo mounting platform machined so that the galvo is set down on the plate, pushed forward against the milled shoulder and the screws tightened. Since the height of the center line of the optical system is fixed, and the azimuth of the track is fac¬ tory adjusted parallel to the base, there is but one adjustment necessary, track position, when the galvo is changed. With the present system of mounting, sound track position, azimuth, and optical axis alignment with the center of the sound roller, may be changed in an attempt to adjust any one of them. To accomplish this improved method of mounting the galvo, a filter condenser under the camera base must be relocated and the necessary holes drilled for mounting screws as well as access holes for tightening them. We now have complete information on the ad¬ justments necessary when the repaired or modified galvo is reinstalled in the recorder. Three major adjustments are required, in addition to focusing; (1) alignment of center line of the optical system with center of sound roller, (2) sound track position, and (3) azimuth. These are the adjustments for which a charge of $10.00 per hour is made at GPL. The preferred way of making the azimuth adjust¬ ment requires the use of a special alignment tool, costing $90.00. This is a slit mask which replaces the mask normally used in the recording system. We hope to have this information on its way to you before this is published. While the cost of the alignment tool is high, a group purchase of a num¬ ber of these would bring the price down. When an improved method of mounting has been settled, you will be provided with the information so that it may be done locally. Mr. Belcher and Mr. Kelley believe that by performing the machining operation locally you can save several hundred dollars as well as minimizing the time you are without the use of your recorder. —NAEB— For those of you who have film processors, the J. A. Maurer Co. is making a nylon film roller for use in processing machines. This newly designed roller has no metal parts and features sleeves and retaining rings of linen-base bakelite and glass ball bearings encased in nylon bearing cages. The rollers are unaffected by and will not affect industrial or processing solution or films. Prices and quantity discount schedules are available on request. —NAEB— We want to call attention to a paper presented at one of the briefing sessions at the NAEB Convention in Omaha, “Techniques of Off-the-air Pickup of Television Signals”. It was presented by Jack Beever, applications engineer for the Jerrold' Electronics Corp¬ oration. We are mailing these to Chief Engineers of all ETV stations. We have extra copies which will be sent to others interested up request. —N A E B— Patricia Green Swenson, manager of KBPS, the Portland Oregon Public Schools AM Station, sends us a report by her chief engineer, Harold Potter, on methods they have used in combatting radio inter¬ ference caused by fluorescent lights. She also asks whether the modernization of school lighting has caused this same problem in other cities, and if so, what has been, is being, and can be done about it. KBPS has been using two types of filters which they have found effective in four out of five cases. They are the Cornell-Dubilier, Model IF-18 and the Sprague, Model F-400. The major disadvantages of using the filters is their cost and the labor involved in installing them either on the receivers or in the electrical outlets. Here is a chance for our readers to help in the solution of this problem. Please send your comments and suggestions to KBPS with a copy to me at NAEB Headquarters. —NAEB— Another excellent paper was presented at a brief¬ ing session of the NAEB Convention in Omaha by Richard F. Vogl, manager of WOI Radio. Its title is “Three Years of Stereophonic Broadcasting at WOI.” The paper presents their experiences in stereophonic broadcasting and we believe, it is of in¬ terest to all NAEB member stations. We’re having it mimeographed and are mailing a copy to all chief engineers of educational radio and television sta¬ tions. If we miss any one, we’re sorry. If you’ll drop us a card we’ll be glad to mail you a copy. —N A E B— We’ve had an inquiry from Marshall Gunselman, Director, Audio Visual Center, David Lipscomb Col- 4 ENGINEERING NEWSLETTER