Re: [TenTec] Solid state amps

[Bill Fuqua <wlfuqu00@uky.edu>]

	Interesting item. By coincidence I am working on a power tube tester 
today. I built one some time ago to check 4CX250B tubes because we go thru 
a lot of them here.  I built a pulse tester that basically applied a large 
negative cut off voltage to the grid and then switched it to zero for a few 
microseconds and measured the pulsed plate current.  This worked just fine 
but if the tube arced over I had to replace the hard to find high voltage P 
channel MOSFETS. So, I have gone to a different grid pulsing technique 
that  uses a more common N channel MOSFET and is transformer coupled to the 
control grid. It seems to work great even with positive grid pulses over 2 
amps. Now I can use it to check high mu triodes as well. I have lots of RF 
power tubes at home and this way I can test them with out having to have an 
amplifier. Even though the plate current may be several amps the DC Plate 
supply only needs to be good for a milliamp. or so.
	I simply compare the results with the data sheets to see if the tube is 
near spec.. This seems to work with in 10 or 15 percent using a new tube.

73
Bill wa4lav
  

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