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servicing of the equipment for theater work. The major electrical considerations, of course, are the Underwriter's requirements, and in addition, the utmost in component reliability due to the economic necessity of installing singlechannel equipment with no stand-by or emergency service available.
The booth equipment consists of two short racks, one the projector control, the other the monitor rack. There are ten major units of equipment as shown by their respective blocks, and in addition, the necessary terminal boards and a high-voltage control panel.
The signal would enter the signal selector, which contains the video amplifier and synchronizing circuits, to be distributed to the control panel, the vertical deflection, and horizontal deflection units. An 800-ma, 400-v power supply makes regulated 300 v available through the regulator unit. The 400-ma, 400-v power supply furnishes power for the horizontal deflection and is fed from a 1-kw, regulating-type transformer which also provides a standard of reference for the high voltage. An offthe-air receiver and picture monitor complete the complement of the racks.
A typical chassis unit is shown in Fig. 7, as it is mounted in the rack and ready for operation. A removable cover can be taken off to check the tubes or the fuses. All individual chassis have the primary power fused, as are the plate voltages which have neon indicators on their circuits. The unit shown is the vertical deflection amplifier; Fig. 8 shows the interior exposed for servicing or adjustment of the infrequently used internal controls: the vertical hold, vertical size, vertical linearity and, on the rear panel, the vertical centering.
Miniature tubes are used whenever possible and, in order to avoid mounting of parts on those small tube sockets and to make the unit more accessible for manufacture and servicing, resistor boards are used to produce this trim design. The mechanical design was so proportioned to permit standardization of the chassis blanks and the covers; in addition, it presents a uniform overall appearance.
Circuit Operation
Electrically, the protection of the 7NP4 kinescope required a major part of the design effort. The expense of the
Fig. 7. Vertical deflection chassis, without cover. Ralph V. Little, Jr.: Theater TV Equipment
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