DRYDEX TYPE 1001 GRID BIAS BATTERY, 1940's

Grid Bias battery of 9 volts with taps down to 1.5 Volts, In early directly heated valve receivers there was no automatic bias for the valve grid, a battery was used to bias the valves grid negative for the correct operation of the valve.

Bruce Hammond Collection

Your comments:

• In the 1950s, as a teenager, I made up 1 valve radios using the HL2 triode and probably S. G. Brown Type F headphones. Two grid bias batteries were just about enough for the anode supply. I couldn't afford expensive 90V or 120V batteries. Happy days.
  .......... Tony, Bridport UK, 22nd of October 2012
  
  

A1506