> > > >

1954-55 Theatre Catalog, 12th Edition, Page 294 (258)

1954-55 Theatre Catalog, 12th Edition
1954-55 Theatre Catalog
1954-55 Theatre Catalog, 12th Edition, Page 294
Page 294

1954-55 Theatre Catalog, 12th Edition, Page 294

DIAGRAM showing the Ashcralt air cooled heal deflector which eliminates 30 per cent of heat.

AG thtact.,Head

Several years of study, research, and development have produced the new AG contact head which is said to be the most perfect means of com-mutating the arc current to the rotating positive carbon presently available.

Not only does the new AG contact head perform the above function over long periods of time without the necessity of frequent replacement parts, but it also controls the heat generated and conducted rearwardly through the carbon, which heat not only deteriorates the core and shell of the carbon, but which would also have a deteriorating effect on the component parts of the contact head itself. This latter function is accomplished by means of a system of ducts in the forward section of the contact block, through which water continually is forced by means of the Ashcraft water circulator.

Obtaining BestScreen Light

After the arc has been regulated so that the two carbons remain on the indicating lines of the arc scope screen, the projector should be set in motion without film. The light should be thrown

upon the screen. With hands on both the negative and positive manual control knobs, the entire arc should be moved slightly toward and away from the reflector. One point will be reached when the light is brightest, the distribution good, and the color whitest. This is the point where the arc should always be operated. Setting of the arc scope may now be made and locked into position.

Another method of determining the best position of the crater relative to the reflector, and at the same time checking the optical alignment, is by means of a pin hole aperture. These special aperture plates may be obtained from the various projector manufacturers.

A target, or any piece of light paper is held about 18 inches in front of the

THIS Auto-Becirculalor is another aid which helps lo make the Super Power a better lamp.

projection lens. When the light is projected through the pin-hole aperture the disc of light on the target should be

uniformly illuminated by moving the crater toward and away from the reflector, the ideal position may be determined. When the crater is too far forward, a brownish color will appear, when too far away the field will be blue, but in the proper position it will be of uniform brilliance.

Carbons and Arc Current

The 10mm high intensity projector carbon (or equal) has become generally accepted as the carbon most suitable for maximum screen brillianceemaximum light distribution together with reasonable carbon economy. This carbon has a current range of 85 to 105 amperes. In that range, screens with widths of 20 feet to 70 feet, or even larger, can be properly illuminated. Very large screens will require certain reflective finishes. No definite rules can be made as there are many factors which may increase or decrease the final results, such as focus, speed of lens, etc.

From our experience a theatre with good lenses, good projectors and a good screen does not require excessively high are currents to obtain excellent screen illumination. The average screen of 30 to 50 feet wide may only require a current of 90-95 amperes, while the larger screens of 65 feet in width to the very large screens may require 100 to 105 amperes.

The rate of carbon consumption undoubtedly will have a strong bearing on the current used. Very few, if any, theatres would use a new carbon for every 2000 foot reel of film, but if two double reels 4000 feet can be obtained from each carbon then the consumption is well within the economic range. It remains to the judgment of the exhibitor and projectionist to determine the current required to project the amount of light required.

If a moderate current of 90 to 95 amperes is used we suggest that a 5/16 by 9 negative carbon be used, but in the 95 to 105 ampere range an 11/32 by 9 inch negative will be necessary to pre

vent excessive spindling. A reasonable amount of spindling is advantageous to prevent wandering of the arc which might occur if too large a negative carbon is used.

The use of 10mm carbons at currents above 105 amperes will require special carbons. The advisability of using these special carbons is questionable as the 10mm standard carbon at 105 amperes produces substantially the same quantity and quality of screen light as special carbons at 123 to 125 amperes. It cannot be assumed that the light projected is directly proportioned to the current used. This is not a fact. We repeat for the best light with reasonable economy the standard 10mm by 20 high intensity projector carbon (or equal) will give very satisfactory results even on very large screens.


Adequate ventilation is one of the most important factors for successful operation of the Super Power Lamp. A draft tube extends directly over the arc from the lamphouse top to the top of the reflector ring. Sufiicient draft should be applied to the six inch lamphouse stack so that when a sheet of paper is held approximately one and one-half inches from the lower end of the draft tube, it is snapped smartly up to the tube. The flow of air should not be lazy, it should be sufficient to draw off all the arc smoke and heat, in fact, the upper portion of the tail flame should be drawn into the draft tube.

If sufficient draft is appliedY even on steep pitches such as 25 to 27 degrees, there will be no indication whatever of smoke deposit on the upper portion of the reflector.

The Super Power Lamp is equipped with a special ventilating door. The row of screened holes at the bottom, together with a row of baffled holes in the lamphouse base, allow an enormous amount of air to pass through the lamphouse without disturbing the arc.

Heat at the Aperture

With currents at from 85 to 92 amperes, there is a possibility of excessive


l .
1954-55 Theatre Catalog, 12th Edition, Page 294