[Amps] testing 572 B tubes

[R@contesting.com]

On Mar 4, 2006, at 3:44 AM, Peter Chadwick wrote:

> If the tubes are soft, there will be (usually) a blue glow between 
> electrodes when drawing current (I have seen it tend more to purple).

Low emission causes gas ionization?

> The emission could be down, which would explain the problem: you could 
> maybe rig up a pulse tester, and pulse the grid positive and measure 
> the plate current. That could be done with a series load resistor 
> 91000 or 1500 ohms at 50 watts, rated for lots of volts!) in place of 
> the RF choke and tank circuit and pulse circuit, and pulse the 
> filament negative by about 70 volts for a 10ms or so. See what the 
> plate current is. All seems a bit messy, though....
>
> 73
> Peter G3RZP
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>



Rich Measures, 805.386.3734, AG6K, www.somis.org