[600MRG] How tough are your tubes?

[Edward R Cole]

At 07:22 PM 1/25/2013, Ralph W5JGV wrote:
>I had an "interesting" anomaly occur this afternoon.

snip-----------


>...let's see now;  3200 Volts x 0.5 Amperes = 1600 WATTS PLATE
>DISSIPATION!!   That's only 4 times the rated value for the tube.
>
>Try THAT with your sand-state devices!

Actually I did run my 300w PA with maxed current when I first tested 
it.  I got output for about a minute when the ferrite beads in the 
RFChoke started popping with smoke let out shortly after.  Pair of 
new MRF422 required...$146.

Turns out I wired the output transformer incorrectly with positive vs 
negative feedback.  Really gets the 28v PS humming.

With new transistors and properly wound output transformer I draw 17A 
at 27vdc (459w dc input) for 270w RF output (59% eff.).  This is a 
CCI EB27A amp kit.

73, Ed - KL7UW


><G>
>
>73,
>
>Ralph  W5JGV - WD2XSH/7
>
>
>
>
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