Huh? Tubes Running with 12V on the Plates?

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Huh? Tubes Running with 12V on the Plates?

Postby Harry Dalek » Fri Aug 05, 2022 11:11 pm

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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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Harry Dalek
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Re: Huh? Tubes Running with 12V on the Plates?

Postby Steve Anderson » Sat Aug 06, 2022 12:13 pm

With some types, yes. There are a number of videos and articles 'out there' I have tripped across over the years though I have no links for them. Sometimes they use 'standard' types, but also those designed specifically to run with a 12V anode/plate voltage for use in cars. Most of these are of the 'space charge' type where the G1 is deliberately used with a positive bias voltage. They are a specialist area of tube use and because of that there's plenty of NOS (New Old Stock) versions available real cheap as no-one wants them.

In a similar vein "Compactron" tubes are cheap and plentiful. Try here...http://www.junkbox.com/electronics/Comp ... ndex.shtml
The tubes and bases still available, again cheaply for the same reason, and worth thinking about.

As for using standard tubes at low volts, it can be done, but the results don't really deliver, not really worth the effort in my opinion...a novelty...if it were any good manufacturers would have used the concept to make their products cheaper, they didn't.

To use conventional tubes in a car radio the 'vibrator power supply' was developed. I remember these from the 60s (just). When you turned the radio on you heard a low buzz or hum before the tubes warmed up and delivered sound.

https://www.radioremembered.org/vpwrsup.htm

Steve A.

I just noticed the 'junkbox' link I added is very similar to the first one Harry listed...
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Re: Huh? Tubes Running with 12V on the Plates?

Postby Harry Dalek » Sat Aug 06, 2022 4:45 pm

I started off with radio shack Tandy electronics science fair kits no soldering just twisting wires together ,one of their kits i made was was a 1 Valve TRF radio ,i recall using 2 or 3 large batteries like shown below ,i think the heater was very low so just needed a 1.5 that was a long time ago those kits were great fun .
http://www.netzener.net/index.php/10-pr ... e-am-radio.

Yes i think running them to low it might just work Steve But interesting for sure ,i was wondering if others have ever tried .
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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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Harry Dalek
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Re: Huh? Tubes Running with 12V on the Plates?

Postby Steve Anderson » Sat Aug 06, 2022 7:22 pm

Many and various HT batteries were available up until the early 70s, but transistor radios having displaced almost all tube based radios overnight the 'tube portable' radios, they were quickly discontinued. I recall seeing 22.5V versions (also used in camera flash units with single-use bulbs), 45V, 67.5V and 90V. Maybe others too. The tube filaments/heaters used either one or two 1.5V cells.

There were quite a few articles and adverts in Practical Wireless and similar magazines in the 50s, 60s, and 70s for 'Battery Eliminators'. These ran off 120/240V and replaced the (somewhat expensive) batteries. Though your 'portable radio' wasn't quite as portable as before unless you put batteries back in it.

It was an expensive luxury to be able to listen to the cricket commentary on the BBC whilst having a picnic...

Steve A.
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