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1947-48 Theatre Catalog, 6th Edition, Page 488 (472)

1947-48 Theatre Catalog, 6th Edition
1947-48 Theatre Catalog
1947-48 Theatre Catalog, 6th Edition, Page 488
Page 488

1947-48 Theatre Catalog, 6th Edition, Page 488

THE CRYSTAL RECTIFYING PROBE adopts the RCA VoltOhmysi and Channulyst for circuit testing of television and other VHF applications. It employs a germanium crystal to rectify applied cr.c. voltages which are measured by the d.c. circuit of the meter. This versatile probe is equipped with an alligator. clip around lead and a special connector and detachable phone plug for use with the VoitOhmyst.

use at the highest frequencies, where the lead length becomes an important factor in over-all accuracy.

The probe cable is equipped with special VoltOhmyst connector and detachable phone-plug. The plug is provided for use with older models of the VoltOhmyst and Chanalyst. When the probe is used with later models, the phoneeplug is unscrewed and the cable can be attached to the meter by means of the special connector.


The RCA battery VoltOhmyst (Type WV-65A) is a self-contained, lightweight vacuum-tube voltmeter which operates independently of any external power source. This means that the meter can be used for servicing equipment in automobiles, airplanes. boats, in rural areas, in industrial electronic applications or other places lacking conventional power outlets. Incorporating the best features of the conventional model VoltOhmyst, the WV-65A now in production measures 9% inches high, 6% inches wide and 6% inches deep. It has five a.c. and six dc. voltage ranges measuring up to 1000 volts; six ohmmeter ranges measuring up to 1000 megohms; and six cmmeter ranges which measure up to 10 amperes.

Used with the newly announced crystal probe (MI-8263), the battery VoltOhmyst is capable of testing voltages up to 100 megacycles.

A neon pilot light mounted in the front panel flashes on and off whenever the selector switch is in either the ff-t voltage," ft- voltage, or "ohms" position, indicating that the instrument is in operation.


The Opti-Focusser is a completely self-contained amplifier (no external power connections are necessary) which was designed for the sole purpose of quickly aligning any motion picture sound optical system, according to the 8.0.8. Cinema Supply Corporation.

Constant vibration of" the entire pro

jector including the soundhead invariably will result in the sound optical tube, holder or associated components moving slightly out of alignment and thereby throwing the sound optical system out of perfect focus. The removal for cleaning or replacement of any soundhead component will also invariably disturb the optical system focus. In the case of the smaller, portable systems, especially 16-mm. equipment, frequent handling, jarring and even dropping will all too often result in optical system misalignment.

Lateral misalignment of the film sound track due usually to wear of the shaft ends of rollers, guides and sprockets also will cause sound distortion, frequency discrimination and noise.

These conditions may be accurately (within 3 db.) compensated for by the novice or the expert in a few seconds on practically any 16-min. or 35-mm. soundhead by the use and application of the above mentioned Opti-Focusser.

A pair of alligator clip leads supplied with the Opti-Focusser are used to make immediate connections to any photo-cell circuit without removing or disturbing any existing wiring merely by clipping them directly to the terminals of the photo-cell socket. Connection may also be made at the end of the photo-cell cable to the prongs or terminals of the connecting plug, or directly to the control grid terminal of the first stage tube in the amplifier.

No connections other than these two simple clip leads are necessary in order to make the required adjustments. A loop of test sound track supplied with the Opti-Focusser is threaded and run through the soundhead during the adjustment period. The operator, using the earphones provided, listens for the loudest and best quality tone while making the necessary adjustments and alignment of the soundhead components. Its just as simple as that.

The theatre amplifier is not used during the alignment, all necessary power and adjustable PEC voltage being supv plied by the Opti-Focusser.

The Opti-Focusser is entirely selfcontained except for an external pair of earphones.

While the adjustment is being made, both hands and both eyes of the operator are free to make the alignment. N0 meters or other visual indicators are used which would distract the eyes or attention of the operator away from the soundhead. All outside voices or dis tractions are most effectively eliminated by the use of the earphones.

The operation is so simplified that quick and accurate aligment can be made with perfect ease between reels and while the other projector is running.

No additional equipment or accessories are required.


When installing new projectors and screens or performing maintenance operations on existing equipmc'nt, servicemen and projectionists have been forced to work without adequate tcst standards for checking picture head performance. As a result, adjusting the position of two projector heads so that both pics tures exactly fill the screen and properly masking the picture being projected were extremely laborious and time consuming. This new type of test film, developed as a service to exhibitors and others, will make checking more efficient and quicker.

The Society of Motion Picture Engineers and the Research Council of the Academy of Motion Picture Arts and Sciences have developed a new 35-min. visual test film to be used by theatre projectionists, service companies and theatre equipment distributors for checking the performance of 35-min. picture heads.

The SMPE Film Projection Practice Committee, under the chairmanship of G. T. Lorance, designed a new series of test targets to provide a convenient check of focus and picture alignment, travel ghost, jump and weave and lens aberrations. '

The film is silent and is made up of four separate target sections: The focus and alignment target, shows whether or not picture size and screen masking are correct, and whether the projected picture is centered properly on the screen.

The travel ghost target shows improper timing of the shutter quite readily and gives an easy indication of the correct adjustment as the timing is

> being corrected.

The jump and weave target gives an accurate indication of the unsteadiness of the projected picture. Picture jump is measured in per cent of picture height, and picture weave is measured in per cent of picture width.

The lens aberration target shows picture distortion and gives an indication of the lack of sharpness that will be present in pictures shown on any particular projector.

The 35-mm. visual test film is 415 feet in length, printed on safety film, and is available from the Society of Motion Picture Engineers and the Research Council of the Academy of Motion Picture Arts and Sciences. It is also available for export with an additional charge for shipping. Some users prefer to use separate loops or continuous lengths of the different target sections

1947-48 Theatre Catalog, 6th Edition, Page 488