B Battery Eliminator

Should you feel the need to power up an old "Farm Type" radio or feel a need to power up a valve or vacuum tube - this is to power the B+ (plate voltage) needs of the tube without the expense of buying 90 volt or 67.5 volt battery.  Use regular low voltage battery to power A+ (tube filament heater).  The C+ power is very old radios with seperate power to tube grids.  Circuits were soon added to power grids from B+ voltage and do away with seperate C+ power. Line voltage at left so be careful and safe.  A polarized plug helps with safety.   Parts list. The 50 nF capacitor is rated at 400 volts ceramic capacitor. 30 ohm resistor is rated at 2 watts. Diode is 1N4003 or could be 1N005.  Might want second connected diode in series as backup if powering up expensive or rare radio. Two capacitors at 22uF are rated for 350 volts. The 3.5Kohm resistor is a bleeder resistor to control voltage at output rated at 5 watts.  Adjust and check values with meter to make sure you have B+ voltage desired. If 67.5 volts is desired try around 2.5 Kohm on far right resistor with 5 watt rating and check with meter. If 45 volts or 22.5 volts is needed.  Add resistors in series to top line between bleeder resistor and output and make sure they have 5 watt rating.  Check voltage with volt meter.

published 7 years ago