On 11/17/2011 5:18 AM, dave wrote:
On Thu, 17 Nov 2011 07:34:03 +0000, Geoffrey S. Mendelson wrote:

Michael Black wrote:


Of course, towards the end of the life of tubes, one could get some
that ran off 12v, intended for use in car radios. Not so useful now
since they were produced in a limited time span as transistors were
taking over, so quantity is relatively limited.

Even rarer were tubes that drew almost no current. They used "cold
cathodes" so they did not need expensive (in terms of current and heat
dissipation) filaments and had low plate voltages.

They came out when transistors where just starting out, but rise of
transisitors was so rapid and transistors were so cheap in comparison,
that it was simpler and cheaper to build a 7 or 12 transistor radio than
a 5 tube cold cathode one.

They showed some promise in the missle and space exploration systems of
the time, because transistors could not stand the temperature extremes
or cosmic radiation they would be exposed to. That also did not last
long, as improved "space grade" transistors came out.

What really killed them was NASA's adoption of the new integrated
circuits (which actually pre-date the "space race").

Cold Cathode tubes were voltage regulators, displays, etc. I have never
seen a cold cathode amplifier.

Between miniature tubes and solid state there were Compactrons, which
were several tube stages in a single envelope.

There were tubes which contained a bit of thorium and required minimal
heater current. The slight radioactivity is a no go, as well as the
potential pollution to the environment ...

Regards,
JS