[Collins] 32S-3 final neutralization question ??

[Dr. Gerald N. Johnson]

On Sat, 2006-07-22 at 09:40 -0700, Glen Zook wrote:
> Having one 6146A and one 6146B is definitely "bad
> news"!
> 
> Look between the 6146 tube sockets.  If there is a
> ceramic trimmer capacitor then this is the "old"
> neutralization circuit and using 6146B tubes will
> almost certainly cause the capacitor to "burn up".  If
> the capacitor is an air variable then the transmitter
> has the newer neutralization circuit and the 6146B
> tubes should work fine.
> 
> You can "mix" a 6146 with a 6146A / 8298.  But, NEVER
> mix a 6146B / 8298A with any of the earlier version
> tubes.
> 
> The article on the 6146 family of tubes is again
> available from the K9STH website (URL of which is
> listed at the end of this message).
> 
> Glen, K9STH
> 
At the Des Moines hamfest last April, Warren Amfahr took credit for the
RF feedback and general linearity of the KWM-1 and claimed that the 6146
was rated by RCA as purely a class C tube, but for him, RCA created the
6146A with significantly better linearity. That would say we ought to
avoid the 6146, though my 32S-1 manual lists the PA tube as 6146. The
Rockwell 3A manual calls for a 6146B in the parts list but 6146A on the
schematic. Now to add confusion, my 32S-3 manual shows 6146A on the
schematic and in the parts list but shows the same part number as the 3A
book has for 6146B. Both schematics show the air trimmer for
neutralization which is the 6146B modification. Somebody wasn't watching
very closely!
-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer