[AMRadio] 20V3 bulbs

Donald Chester k4kyv at hotmail.com
Sun Jan 16 15:22:46 EST 2005

>My Collins 20V-3 has those dropping resistors as well.  Seems like the
>"experts" blew this one.
>Oh, well, not everyone can be perfect.

Actually, the 120 volt bulbs with dropping resistors should last longer.  
The series resistance will buffer the inrush current.  The cold filament of 
an incandescent lamp has but a fraction of the resistance of a hot filament. 
  The series resistor will limit the current until the filament heats up.

The Gates BC1-T also uses those bulbs.  Right now mine are running off the 
DC control voltage I modified into  the rig.  I'm going to have to change 
the circuitry, because the bulbs have a very short life when they run off 
DC.  I forget what it is called, but there is a physical effect that causes 
incandescent filaments tot to last long on DC, even though the effective 
voltage is the same as their rated a.c.  voltasge.


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