[Boatanchors] Valiant 6146 Question

[Glen Zook]

The differences in the interelectrode capacitance may have had something to do with the problems.  However, the differences are really not that much.  I haven't tried disassembling examples of each type.  There may be something in the actual layout of the elements which contributes to the fact that the 6146B/8298A and 6146W are harder to neutralize.
 
Glen, K9STH


Website:  http://k9sth.com


________________________________
 From: Jim Wilhite <w5jo at brightok.net>
To: 
Cc: boatanchors at mailman.qth.net 
Sent: Wednesday, December 19, 2012 4:10 PM
Subject: Re: [Boatanchors] Valiant 6146 Question
 
You made me think a bit more Glen.  I dug out my old ARRL handbook that had tube specs in it and looked up the 6146.  The Interelectrode Grid 1 to Plate in the old tube is .22 pf and in my later book (c. 1970s) it is .24 pf.  The Grid to cathode in the old is 13.5 and the newer version is 13.0  The plate to cathode is 8.5 in the old and 8.5 in the new.  

So there were redesigns of the tube later along accounting for a small change in neutralizing and, as you describe in the Collins equipment particularly, the cap was already marginal.