Old variable transformer.
Claude Lyons variac repairs Part 1
Variable Transformer Repairs part 1 - Initial inspection and Dismantling.
Claude Lyons variac repairs Part 2
Variable Transformer Repairs part 2 - Testing and Cleaning.
Claude Lyons variac repairs Part 3
Variable Transformer Repairs part 3 - Fitting new parts and reassembly.
Claude Lyons variac repairs Part 4
Variable Transformer Repairs part 4 - Electrical and operational testing.
Variacs or variable transformers are used to vary the voltage applied to a device. Typically there are two configurations, 0-240V out and 0-270V out.
The input is the normal 240V mains supply.
This is useful for testing purposes as voltages may vary in different locations, speed controller for certain types of motor, or lighting dimmers for large installations.
This example is a Zenith brand, distributed by Claude Lyons.
It is contained in a heavy metal case, and was probably manufactured in the 1960s.