Re: [Amc-list] Tube radio caution...

[Tom Jennings <tomj@xxxxxxx>]

On Fri, 1 Feb 2008, Frank Swygert wrote:

> These days we're all pretty used to turning the switch to
> the ACC position and listening to the radio for a couple hours
> then getting right in and starting the car. Well, maybe not
> if you have a high dollar system with a couple amps and such,
> but with a stock stereo or aftermarket head unit with no (or
> relatively low power) external amps you can easily do that.

This one particular tube radio is actually low-powered, but
most of them really are pigs for DC. Tubes use .15 amps just
to heat the filament; the high-voltage supplies are really
inefficient, and overall older tube circuits are designed to
be cheap, not power-efficient.

A 5 amp load on a small battery with a tired generator is not
a good combination!

I still like them though.

This 62 radio (Bendix 22BA) is an oddball, very very late in
the development of electron tubes. There's only two tubes to
start with, and the plates run directly off 12V, they don't
need high-voltage. Earlier ones, especially the big tubes and
ones with vibrators, are really power pigs.

At the end of the 50's/early 60's a lot of really interesting
vacuum tube deveopment was done, right before they all became
worthlessly obsolete. Low-voltage tubes, sub-sub-miniatures,
Nuvistors, ... and the submini tubes developed for torpedo
triggers and proximity bombs in the early 40's are still pretty
amazing (they went into hearing aids post-war). Subminiatures
were used up into the 70's -- by the 60's good circuit design
got predictable 16,000 hour life from them.


> On a side note, the Soviets (well, Eastern Europe now!) didn't
> adopt transistors until much later. When the US got ahold
> of a Foxbat interceptor in 69 or 70, one of the things some
> unknowing journalist ridiculed was tube technology in the
> electronics. They failed to note that 1) Tom will be able to
> listen to his radio after a nuclear blast, the rest of us may
> be out of luck (tubes are resistant to the electromagnetic pulse
> that will fry transistors, and this is a cold war interceptor!);
> 2) The soviets continued developing tubes when the US stopped,
> so they weren't the same old tubes from 40s technology that they
> thought they were, they were much more advanced than any tubes
> ever made in the US.


Yeah, the Russians were not/are not stupid. There certainly
was a large element of unable to innovate new gadgets but man
the Russians do good engineering!

Reliability is a funny thing -- reliable things are rarely
"cutting edge" tech. A device with 10, 20, 30 years of use,
research, aggressive development, careful tuning can be a
damn good device. The major downside to tubes in most apps is
that they are power hungry and large.  But if you accommodate
those things, they're fine. And as we all know, skilled and
knowledgable use of a simple tool often beats high-tech.

Not that I want electron tubes in anythign more than Rambler
radios or fun (non-critical function) desktop gadgets... :-)

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