LIQUID-COOLED POWER AMPLIFIER.

The amplifier described in this article was developed as a part of a research program in which it was employed to excite magnetic specimens. The original model was designed to produce peak currents slightly in excess of 10 amperes at frequencies ranging from zero to 5kHz, but operating experience indicated that the equipment was capable of being uprated by a substantial amount. In this amplifier, cool liquid is pumped into a small tank to equalize the pressure applied to the branches and the coolant is then passed through four short lengths of polythene tubing to the output stage transistor bank. After cooling the transistors the warm fluid is returned to another tank from which it flows to a fan-assisted heat exchanger of the type commonly used for car heating. Various liquids were considered for the coolant, but the final choice was water with a little ″Prestone″ inhibitor added.