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Space Charge tubes operate at "safe" voltages. Normally 12 volts. Just as Compactron tubes were the last gasp for tubes in TVs, the space charge tube was the last gasp for tubes in car radios. While the concept had been around since the 1920s, because of the poor efficency, the design concept was not used in tubes until around 1958 when Tung-Sol designed a line of space charge tubes for use in car radios. The large battery in the car ment that the higher power requirements of space charge tubes was not as much an issue. The primary advantage was that the tubes allowed the elimination of the vibrator circuit in the car radio. The vibrator was a device used to convert the DC power in the car into AC so it could be boosted to high voltages for use by the tubes. However being a mechanical device, the vibrator had a short life expectancy. The use of the space charge tube had a narrow window. To be usable, the space charge tube needed the development of the transistor to happen. There are no power output space charge tubes, so transistors were used for the output. Once low cost high frequency transistors became available in the mid 1960s, the space charge tube became obsolete. These days the big advantage of the space charge tube is that it operates at non-lethal voltages (12 volts to 33 volts). The main disadvantage of the space charge tube (besides there not being any high power output tubes) is that many of them require much higher heater current to operate. That means that they get hot.

Jeff Duntemann has an excellant article on space charge tubes.
http://www.duntemann.com/12vtubes/12vtubesindex.htm

Alternate link:
http://www.junkbox.com/electronics/lowvoltagetubes.shtml

When considering a tube project that will be operated from batteries, a
Battery Radio Tube
should be the first tube type you should consider.

If you have lots of portable power available (such as in a car), or you are operating from a low voltage power supply, consider looking at a space charge tube. Space charge tubes draw heavy on heater current, but only need 12 volts for plate operation thus eliminating the need for an additional high voltage plate power supply.

For more information on battery radio tubes see
Battery Radio Tubes

A listing of battery radio tubes we have available can be found here in
Our Battery Radio Tube List

How To Order:

Purchasing our Space Charge Low Voltage tubes is easy.
Click on the desired link above to find the tubes you need.
Then just send us an email indicating the tubes (including quantities) you want.
We will let you know the total price including shipping and handling.

Shipping and Handling Information

Contact MDB Ventures
sales@mdbventures.com
or
sales@fourwater.com

Due to the highly volatile nature of the tube business, all Prices are subject to change without notice.