50a1 Replacement

12/12/2004 3:11:36 PMLew

In a Trans oceanic radio, what are the disadvantages of replacing the 50a1 with a 1K wire resistor?

12/12/2004 9:43:48 PMNorm Leal

Hi Lew

The 50A1 gives some regulation over a wide range of line voltage. Your resistor won't have this regulation. Most other radios only used a resistor to drop filament voltage.

You can select a resistor to give proper filament voltage. The filament string draws around 50 ma.

Norm

:In a Trans oceanic radio, what are the disadvantages of replacing the 50a1 with a 1K wire resistor?

12/13/2004 10:10:00 AMSteve - W9DX

Lew: Antique Electronic Supply sells a solid-state equivalent to the 50A1 for $16.90 + S/H. I used one in my TO L600 and it works great.
Steve

:Hi Lew
:
: The 50A1 gives some regulation over a wide range of line voltage. Your resistor won't have this regulation. Most other radios only used a resistor to drop filament voltage.
:
: You can select a resistor to give proper filament voltage. The filament string draws around 50 ma.
:
:Norm
:
::In a Trans oceanic radio, what are the disadvantages of replacing the 50a1 with a 1K wire resistor?

12/18/2004 5:51:39 PMTom S.

:In a Trans oceanic radio, what are the disadvantages of replacing the 50a1 with a 1K wire resistor?

Lew: One good method of doing this is to install a 9 volt 1 watt zener diode at the head end of the heather string. Then, with 120 volts applied, adjust the value of series R (the 50A1 sub) so that the zener conducts about 5 ma and use this value for your resistor. This puts regulation back into the heather circuit and also offers heater protection that the 50A1 did not afford. Good luck.