29 Jul
2007
29 Jul
'07
12:13 p.m.
On 29 Jul 2007 at 14:30, Roy J. Tellason wrote:
I remember having an assembly consisting of a pair of
those, rated at
500mA (you could tell by size :-), and a couple of 100uF caps, which
in those days was a pretty big cap, in a voltage-doubler
configuration. I probably salvaged it out of some old TV...
You used to be able to find them in everything from battery chargers
to HO train set power supplies to TVs. They didn't make much of a
splash in AM radios, particularly the "All American 5" variety.
I still have the stink of hydrogen selenide from those things etched
into my brain (when they went bad). Like hydrogen sulfide but more
pungent--and more toxic.
When you replaced them with silicon diodes in HV supply applications
(IR used to offer complete clip-in cartridge diode assemblies), it
was customary to include a small-value series resistance.
Apparently, seleniums were better able to handle the surge from the
usual pi-section filter where the input capacitor was fairly large
(40-50 mfd).
Older battery chargers used copper-oxide rectifiers as well as Tungar
bulbs.
Cheers,
Chuck