name this part

Thread Starter

ajrenzetti

Joined Dec 20, 2010
40
at one point i was going to try to make an induction heater based on this schematic, but i could never figure out exactly what kind of tube was used in it. so, does anyone know the name of the part circled in red in the schematic picture? ive included the image link as well in case you cant see the other picture loaded from file.
 

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Adjuster

Joined Dec 26, 2010
2,148
It looks like a type of triode to me, but unfortunately I don't know much about tubes :p
It looks a bit that way, but there is no DC return path from the end that looks like the cathode - just a capacitor. I thought maybe some king of triggered gas tube, if the supply is AC?

Or perhaps the schematic has simply been copied incorrectly, maybe by someone unfamiliar with standard component symbols.

Edit: Triode tubes are used in such applications: some of them are really rather big. This one delivers 1.25 Megawatt, with 17.5kW needed just to heat the cathode.

http://www.thalesgroup.com/Portfolio/Documents/Triode_RS_3700_CJ/?LangType=2057
 
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Adjuster

Joined Dec 26, 2010
2,148
The symbol may look like a magnetron, but the circuit shown seems to have external frequency determining parts, and there is no DC path through the device.
 

tgotwalt1158

Joined Feb 28, 2011
110
I think its an old model of triode known as 955 triode. The author seemed to have drawn grid and cathode scantly, may be due to be in hurry.
 

K7GUH

Joined Jan 28, 2011
190
By convention, the heater is often omitted from tube diagrams. I don't understand why one would expect a DC path through the device.
 

Adjuster

Joined Dec 26, 2010
2,148
By convention, the heater is often omitted from tube diagrams. I don't understand why one would expect a DC path through the device.
A DC path through the circuit is required, which is what I was referring to, if this is a vacuum electron tube. Conduction can normally only occur by electrons leaving the heated cathode and moving towards the other electrodes*. In this case however, what looks like the cathode is only connected to a capacitor, so no DC current flow is possible.

Typically a vacuum tube circuit might decouple the AC voltage at the cathode to common with a capacitor, but there would also be some DC path via a resistor or a choke etc.

*Edit: Secondary electron emission may occur from other electrodes, but first there must be a path for cathode current.
Do we assume this may be implied, like the heater connection? In which case, why show the HT input at all?
 
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Thread Starter

ajrenzetti

Joined Dec 20, 2010
40
wow i didnt expect this many posts for the question.

i cant really tell if this would even work at all. i would have said no a long time ago if the schematic didn't come from a legit corporation for ceramic capacitors. could the tube instead be some kind of vacuum capacitor? maybe an adjustable one?
 
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