Chuck Harris wrote:

Today it is trivial to make a simple switching power supply that can provide
a couple of hundred volts at 98% efficiency, why not make one of them, and
use some real tubes?

The problem I've encountered with switching supplies is that they're so
blasted noisy because of the fast risetimes in the high-current parts
of the supplies and because they're usually not very well shielded and/
or decoupled.

--
Ah, yes, _The Dying Earth_: a wonderful title, greatly spoiled by the
book.

-- Nix, in a newsgroup inhabited by a better class of people

"Mike Andrews" ) writes:
Chuck Harris wrote:

Today it is trivial to make a simple switching power supply that can provide
a couple of hundred volts at 98% efficiency, why not make one of them, and
use some real tubes?

The problem I've encountered with switching supplies is that they're so
blasted noisy because of the fast risetimes in the high-current parts
of the supplies and because they're usually not very well shielded and/
or decoupled.

But given the topic, I'm always surprised that people don't treat switching
supplies like those cars of old. Look in the old ARRL mobile manual (and
a later edition just might have a receiver using those 12v tubes), and
there was always material about filtering the alternator noise.

Make it go through feedthrough capacitors, put in tuned circuits in
series with the 12V (to null out the whine), and good shielding. These
are the things that apply to switching supplies, though too often they
are so treated as black boxes that nobody considers such things.

As for 12v tubes, you most certainly saw converter using them. SOmeone
was asking about 12v Nuvistors a while back, and the next to last edition
of the ARRL VHF Manual, late sixties or so, has a converter using one.


Michael

Michael Black wrote:

As for 12v tubes, you most certainly saw converter using them. SOmeone
was asking about 12v Nuvistors a while back, and the next to last edition
of the ARRL VHF Manual, late sixties or so, has a converter using one.

We are not talking about normal radio tubes that have 12V heaters, we are
talking about special tubes that have 12V heaters, and a 30V maximum plate
voltage rating. These special tubes were designed to use normal car battery
voltages as their plate voltages.

-Chuck

Mike Andrews wrote:
Chuck Harris wrote:


Today it is trivial to make a simple switching power supply that can provide
a couple of hundred volts at 98% efficiency, why not make one of them, and
use some real tubes?


The problem I've encountered with switching supplies is that they're so
blasted noisy because of the fast risetimes in the high-current parts
of the supplies and because they're usually not very well shielded and/
or decoupled.

If you make it yourself, you can apply proper shielding and decoupling techniques.
It is done all the time in commercial radios. For a small receiver like is
being discussed here, the supply can be made in a couple of cubic inches...
Something that can be easily made in a soldered shut can with feedthru's on
all of the leads.

-Chuck

Back in the late 1950's, hybrid auto radios with 12 volt plate tubes for all
except the audio output stages were built by Automatic Radio for Ford and
Chrysler. The first production was in 1958. A Motorola power transistor was
used in the audio output stage. A search through Sams Fotofacts for 1958 and
later should give you some schematics to start with. A trip to an auto
junkyard might give you a radio.

Kilcummin wrote:
Back in the late 1950's, hybrid auto radios with 12 volt plate tubes for all
except the audio output stages were built by Automatic Radio for Ford and
Chrysler. The first production was in 1958. A Motorola power transistor was
used in the audio output stage. A search through Sams Fotofacts for 1958 and
later should give you some schematics to start with. A trip to an auto
junkyard might give you a radio.

If you're going to go JunkYardin' for a radio - might as well get a
goodun' - late 50's early 60's era Cad. The WonderBar mechanism is a
treat (and works VERY well) - and all of the tubes (including the relay
driver tube) are 12V tubes (audio out is a single transistor).

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com