OA3/VR75

Octal-base, gas-filled cold-cathode glow-discharge voltage regulator tube designed to maintain a highly stable 75-volt drop across a variable current range of 5 to 40 milliamperes. Equivalents: OA3, VR75, VR75-30, CV375. Real-Life Examples: Hammond AO-28 organ preamplifier (B3/C3 series), Collins 75A-4 amateur radio receiver, vintage military radio power grids.