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Figure 1. The old and the new. At the right is shown the new Type V-5MT, at the left the old Type 200-CM.

Figure 1. The old and the new. At the right is shown the new Type V-5MT, at the left the old Type 200-CM.

General Radio 200cm Wiring
Figure 2. "The new General Radio unit brush . . . can be changed without tools."

which can be changed (Figure 2) without tools. The V-5 Brush has a further advantage in that its low sprung weight reduces hammering and arcing under vibration conditions, injurious to both brush and winding, and it is designed to prevent contact of the brush holder with windings and consequent short-circuit damage. Proper brush pressure is assured by the use of an accurate coil spring, which in turn is electrically shunted so that the spring is not subjected to load current. Brush travel is limited by a resilient stop.

No longer is it necessary to take practically the whole moving assembly apart to reverse a shaft in changing from panel to table mounting, or vice versa. A single screw (Figure 3) loosens the shaft for removal or tightens it in assembly. Brush adjustment and the resilient stop setting are unaffected by shaft reversal.

Figure 3. "A single screw loosens the shaft for removal or tightens it in assembly."

Variacs have to be carried, and knobs are poor and unreliable handles, relying, as they do, on set screws. Figure 4 shows the V-5 cord with molded-on plug which, wound about the Variac and plugged into the Variac outlet, serves as an excellent carrying strap.

Rubber feet, that squeeze back into their sockets for panel mounting, make V-5 Variacs considerate of your bench, table, or desk, and provide sufficient friction to prevent slipping even on smooth surfaces. Rounded contours, devoid of sharp or irregular projections, still further protect against damage to adjacent objects (including hands and feet) in the inevitable bumps and drops that occur in the life of an instrument.

Dials with BIG calibration figures and additional scale points make V-5 Variacs easy to read and to reset. Clockwise rotation to increase output is the rule.

Terminals have both solder and screw connection facilities, are easy to get at, and logically arranged. Barriers reduce the hazard of short-circuits from loose strands. A circuit diagram, integral with the terminal strip, identifies each lead and indicates normal voltages (not turns, as heretofore) between leads as a wiring aid. Extra

Figure 4. . . the V-5 cord with molded-on plug which, wound about the Variac and plugged into the Variac outlet, serves as an excellent carrying strap."

terminals (6 and 7) greatly extend the usefulness of the V-5 Series Variacs when used with supplementary transformers. The terminal strip itself is a high-impact-strength molding, protected by a metal, fiber-lined cover to reduce further the possibility of breakage. If, however, you are ingenious enough to break it, the only tool required for replacement is a screw driver.

Next to a zipper, the V-5 case and terminal cover assembly method is the fastest. Two screws only are required for the assembly of the two pieces to the base. A cover band, carrying integral rivets, cooperates with the screws to form a secure yet rapid assembly. Type numbers distinguishing cased and uncased models are automatically formed by registering tabs on the parts.

A new, heavy-duty switch breaks both sides of the line in mounted V-5 models. Provision is made for polarity indication for use with grounded loads, which, while seldom recommended, are sometimes required.

General Radio Company has never featured appearance for appearance's sake. Yet V-5 Variacs have a distinctly modern look, naturally and functionally derived. Curves instead of angles result from the maintenance of fixed clearances with a minimum of enclosing material. The top "band" is used to position the perforated cover side when it is welded to the top ring. The bottom "band" which forms the other termination of the cylindrical portion of the enclosure carries fastening rivets as previously explained. Both are functional. The flush dial is a perfectly logical method of conserving space and material, as it is eminently suitable to form a portion of the enclosure. The perforations were deliberately chosen to accent the cylindrical nature of the design. Perforations

Figure 4. . . the V-5 cord with molded-on plug which, wound about the Variac and plugged into the Variac outlet, serves as an excellent carrying strap."

were required in any event; better attractive than not.

The finish selected for V-5 Variacs is an exceptionally durable matte baking lacquer. Its lack of high lights prevents distraction of attention and preserves the unity of the basic design. The use of aluminum for structural parts with attendant corrosion resistance is further enhanced by this wear-resistant and attractive covering.

Last but not least, don't overlook the fact that V-5 Variacs deliver 25 per cent more KVA per pound than equivalent 200-C models. Grain-oriented strip cores permit reductions in both iron and copper for comparable ratings. Aluminum instead of zinc and steel in structural parts farthers this weight reduction.

— Gilbert Smiley

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