Tubes Running with 12V on the Plates

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Tubes Running with 12V on the Plates

Postby Harry Dalek » Fri May 12, 2017 6:27 pm

Heres another thing one of endless things i never knew ...interesting
http://www.junkbox.com/electronics/lowv ... ubes.shtml
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Tubes Running with 12V on the Plates

Postby Steve Anderson » Fri May 12, 2017 7:59 pm

Many years ago I had a few car radios that used 12V tubes, worked fine in the shed off a 12V supply...AM only those days. Early 70s, No FM in Victoria in them there days.

I had a 12V tractor battery that powered everything, lights (via an aircraft rotary converter), 12V soldering iron, you name it. I couldn't afford the cable to run from the house as a student, or all the electrical fittings.

Once a week I would drag it back to the house on a trolley I found somewhere and recharge it using dad's car-battery charger.

Eventually dad relented and had 240V AC installed...by a professional, not me!

Steve A.

There were a few that worked on 6V too if you had an old VW beetle...usually positive ground - the car that is...

An example of a space-charge tube is attached, note the maximum plate voltage is 30V!
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Re: Tubes Running with 12V on the Plates

Postby Harry Dalek » Fri May 12, 2017 9:40 pm

Steve Anderson wrote:Many years ago I had a few car radios that used 12V tubes, worked fine in the shed off a 12V supply...AM only those days. Early 70s, No FM in Victoria in them there days.

I had a 12V tractor battery that powered everything, lights (via an aircraft rotary converter), 12V soldering iron, you name it. I couldn't afford the cable to run from the house as a student, or all the electrical fittings.

Once a week I would drag it back to the house on a trolley I found somewhere and recharge it using dad's car-battery charger.

Eventually dad relented and had 240V AC installed...by a professional, not me!

Steve A.

There were a few that worked on 6V too if you had an old VW beetle...usually positive ground - the car that is...

An example of a space-charge tube is attached, note the maximum plate voltage is 30V!


Yes its amazing these things can be made to run on 12 volts or less i also find it interesting you could run normal types at the lower voltage with a slight circuit change ...makes you wonder why they never made them run on the lower voltage at the first place would of been useful in the early days with not many people with mains power as also you experienced...you had batteries not mains power (sounds like a real pain !)
VW'S HAD A POSITIVE GROUND !
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Tubes Running with 12V on the Plates

Postby Klaas Robers » Fri May 12, 2017 11:35 pm

This trick for the low voltage tubes, has been found years after the triode, tetrode and penthode were developed. Then the behaviour of electrons in the space around the grids was understood much better and the trick of the space charge could be invented. At that moment there was electricity in most homes and this wasn't needed any more for stationary use.
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Re: Tubes Running with 12V on the Plates

Postby Steve Anderson » Sat May 13, 2017 11:36 am

Harry Dalek wrote:VW'S HAD A POSITIVE GROUND !

Assuming that was an expression of surprise...not only early VWs but quite a few of cars produced post-war were also positive ground. Also quite a few were 6V. But the cold European winters meant that many 6V cars refused to start, even when they did the lights were dismal.

I believe that the change to negative ground, where applicable, was it was found that negative ground cars were slightly less prone to corrosion. How true that is I don't know. There may have been other factors too. Only having to produce generators (no alternators then) for positive and negative ground versions on a production line for example.

My first car was a 1969 UK-made Ford Escort MkI, all 1100cc of it! But it was 12V and negative ground, it still had a generator, all 22A of it, not an alternator, and a relay-based regulator. Thankfully the wipers, on or off, that was it, no fast/slow or intermittent, were not driven by the manifold vacuum. These vacuum driven wipers went frantically when you were sat at a set of traffic lights and when you really needed them at the breakneck speed of 50mph (80kph) they would almost come to a standstill.

Anyone else remember those? Heck, what we put up with in those days! The Escort also had no radio, 12V on the plates or otherwise, nor even a place to fit one. My fathers first car, a Ford Pop I think, didn't even have a heater...in the UK! Ekkie thump, them were the days!

Steve A.
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