General Radio W10 Variac Variable Autotransformer 120V 10A 50-60Hz Panel

General Radio W10 Variac Variable Autotransformer 120V 10A 50-60Hz Panel

The General Radio Company W10 is a panel-mount variable autotransformer — commonly known by the Variac trade name — designed to provide continuously adjustable AC output voltage from a 120V, 60Hz (or 50Hz) supply. The W10 uses a toroidal winding construction with a carbon brush contact riding the exposed winding surface, allowing smooth and precise manual adjustment of output voltage via a central rotary shaft. This is a bare module unit without an enclosure, intended for panel mounting in a chassis, cabinet, or custom test bench build.

Specifications & What's Included

• Model: General Radio Company W10 Variac
• Input Voltage: 120V AC
• Current Rating: 10 Amperes
• Frequency: 50–60 Hz (marked "50-60 Cycles" on terminal plate)
• Phase: Single Phase
• Output Voltage: Continuously variable, 0–120V AC (rotary brush adjustment)
• Winding Type: Toroidal copper winding
• Terminal Configuration: 5 screw terminals on top-mounted terminal plate
• Terminal Labeling: Common (GND) / Line / Load connections per top-plate diagram (terminals 2 or 4 for line/load)
• Form Factor: Panel-mount module (square aluminum flange with four mounting holes)
• Country of Manufacture: USA (made by General Radio Company, Concord, MA)
• Unit only — no enclosure, no external knob cover, no mounting hardware included

Applications

The General Radio Variac series of variable autotransformers was widely used throughout the mid-20th century in electronics laboratories, test benches, university research facilities, and industrial quality control settings. The W10 panel-mount module was typically integrated into custom test enclosures or bench-built equipment where a precise, manually adjustable AC voltage source was required — for example, testing components at varying line voltages, powering equipment under controlled conditions, or performing voltage stress testing. General Radio Company (later GenRad) Variacs remain sought after in the vintage electronics and surplus lab communities for their robust toroidal construction and reliable brush contact design. This module type is compatible with a wide range of benchtop, rack-mount, or custom chassis applications wherever a 120V single-phase supply is available.

Please note: We may have multiple units of this item in stock. The unit you receive may vary slightly from the one shown in the photos. All units are functionally equivalent and inspected to the same standard.