FW: [NJARC] Re: [Milsurplus] Tungar rectifiers

[bill riches]

____Ebay has some for sale 

Tungar bulbs are gas filled low voltage, high current rectifier tubes. The
name refers to the fact that some are argon filled and have a tungsten
filament cathode. There are mercury vapor versions of these also. Tungar
bulbs were often used in car battery chargers before silicon diodes became
available. Tungar bulbs typically rectified a few amps and had peak reverse
voltage of a few tens of volts, and a forward voltage drop of maybe around
10 volts.
The cathode typically required about 1.5 volts at around 15 amps. Some
mercury vapor models have more complex cathode structures that sometimes
trapped mercury, and the cathode drew even nore current for several seconds
to maybe a minute until the mercury was vaporized from the cathode structure
and the cathode reached normal operating temperature.

In operation with current flowing from cathode to anode, argon filled models
had a dim "fuzzball" of violetish colored glow around the filament. At least
in some models, the filament was so much brighter that the argon glow was
nearly invisible. Argon has a way of being unexpectedly dim at currents
around a few tenths of an amp to several amps. In mercury vapor models, the
glow is light blue and brighter. In at least one mercury model with a more
complex cathode structure and two anodes, the cathode has a dim red-orange
glow that is invisible through the brighter blue mercury glow. The mercury
glow also has a strange pattern, making this bulb possibly useful for
B-grade science fiction movies.___________________________________________

73,

Bill, WA2DVU
Cape May, NJ