[Boatanchors] 6SG7 VS 717A tubes?

[Philip Atchley]

Hi,

I have a National NC-183R setting on the work table, and one of the 
first things I noticed about this set is that there is a Western 
Electric 717A tube in the 2nd IF stage instead of the specified 6SG7.

Now, this 717A is a "peculiar looking" octal tube.  The chrome metal 
octal base is nearly 3/4 inches tall while the glass bulb is only about 
5/8 inches tall and a little fatter than the base.  It is heavily 
"getterized" (shiny silver) and what I can see through the getter 
material looks like a very tiny tube is inside the envelope.

It's neither in my tube substitution book NOR the Hickock 800A tube roll 
chart.  My suspicions lead me to believe that this is NOT a suitable 
substitute for a 6SG7.  Thoughts?

73 de Phil  KO6BB