[Heathkit] off topic question, sort of

[Bob McGraw - K4TAX]

Testing a tube of this type can be done in a very basic manner.  Required 
are various voltage sources and methods to determine accurately voltage and 
current values and  a set of curves for the specific tube.

Heater voltage and cooling for the base in the case of the 4-400
Adjustable bias voltage from -150 to +50
Adjustable screen voltage 0 - 250 VDC
Adjustable plate voltage 0 - 500 VDC

The ability to monitor current of each of these voltages is necessary.  Plot 
the voltage vs. current and compare with the tube curve.  A good tube will 
follow the curves, a bad or weak on won't and an shorted one with show 
excessive current very rapidly.

Of course if you have a known good tube, you can make your own charts based 
on various voltage values.  Just be sure one doesn't exceed the ratings of 
the elements while under test.  If you have many tubes of different types to 
test, I'd consider making a more permanent test bed or test jig using 
variable supplies, accurate volt and current meters.

On the other hand, if you have only one or two to test, I'd consider putting 
it into a working transmitter and comparing the results with known good 
tubes.

73
Bob, K4TAX



>> DOES ANYONE KNOW OF A WAY OF TESTING TRANSMITTER TUBES SUCH AS 4-400. WAS 
>> THERE EVER ANYTHING IN ANY OF THE ARRL HANDBOOKS.
>> SEEMS LIKE THERE MUST BE SOME WAY TO JERRY RIG SOMETHING THAT WOULD DO A 
>> BASIC KINDA TEST.