General Radio W2M Variac Autotransformer 0-140V 2A 120V 50-60Hz Benchtop

General Radio W2M Variac Autotransformer 0-140V 2A 120V 50-60Hz Benchtop

The General Radio W2M is a benchtop variable autotransformer — marketed under General Radio's registered Variac trade name — that accepts a standard 120V AC line input and delivers a continuously variable output from 0 to 140V AC at up to 2 amps. A single rotary control knob with a graduated 0–140 dial allows smooth, stepless adjustment of the output voltage. The unit is wired one side common to line and load, the standard single-phase Variac configuration. It was manufactured in Concord, Massachusetts by the General Radio Company and bears US Patent 2949592.

Specifications & What's Included

• Model: Type W2M (Variac autotransformer)
• Input voltage: 120V AC
• Output voltage range: 0–140V AC (continuously variable)
• Output current rating: 2 Amps
• Frequency: 50–60 Hz
• Phase: Single phase
• Wiring: One side common to line and load
• Control: Rotary knob with graduated 0–140 dial scale
• Output terminals: Two red binding posts
• Enclosure: Gray steel benchtop case
• Manufacturer: General Radio Company, Concord, Massachusetts, USA
• Patent: US Pat. 2949592

Applications

Variable autotransformers of this type are a standard tool in electronics labs, test benches, and industrial service environments. By allowing the operator to dial in any AC voltage from zero up to slightly above line voltage, they are used to bring equipment up slowly during burn-in or fault diagnosis, to test devices at varying voltages, to simulate low-line or high-line conditions, and to power older equipment designed for voltages that differ from the local supply. The General Radio Variac line was one of the most respected in this category and was in wide production from the 1940s through the 1970s; the W2M is a compact, low-current model suited to bench work with small instruments, power supplies, and electronics under test. These units remain actively used today in repair shops, university labs, and industrial maintenance wherever adjustable AC voltage is needed. The Variac trade name originated with General Radio and is now also associated with Technipower (which acquired the line), so units may carry either nameplate — this example bears both the original General Radio name and a Technipower overstamp.