Surge

Mfr: Wuerth Tube-Saver Corporation, 9125 Livernois Avenue, Detroit 4, Michigan. It has patent number 2,756,382 marked on the identification label on the back, along with the address. At the top of the label is "Tube-Saver Model 100A, 117 Volts AC-DC, 150-400 Watts At Receptacle." The little decal on the front says "Patent Pending" so that label must be a little older.

The Tube-Saver is a medium-brown metal box with bronze-colored top and bottom. It's 5-1/4 inches long, 3-1/4 inches high and 2-1/2 inches deep.

It's operating principle is similar to the thermistor method but the construction or the execution of the method is very different. This Tube-Saver uses a large wire-wound resistor in series with the line between the power cord and the load outlet. In parallel with the resistor is a light bulb, which looks like a clear night light bulb, the 4 or 7 Watt kind. And in also parallel is a pair of contacts operated by a bi-metal thermostat type of device. After current passes through the big resistor to the radio, TV or Hi-Fi long enough to heat up the bi-metal element, the contact closes and shorts out or bypasses the resistor and the light bulb and connects the line cord directly to the load outlet on the end of the box. When the voltage drop across the resistor goes away because the contacts closed, then the light bulb goes out. It will only be on while the Tube-Saver is reducing the output load voltage going to the Radio or TV. One thing that doesn't show in the pictures is a small adjusting screw in the same end of the box as the power cord. The screw is actually on the thermostat switch and it adjusts the gap between the contacts, for controlling the time delay before the dropping resistor gets switched out of the circuit.

when TVs and radios had tubes.

mildly funny.