[Boatanchors] One Tuff 6146

[Glen Zook]

The tube should actually be identified as a 6146B / 8298A.  Like most of the older transmitters, the Eico 720 often just doesn't "like" the 6146B / 8298A / 6146W tubes.  Those tubes, generally, need changes in the neutralization circuitry to prevent "taking off" which generates all sorts of spurious emissions plus additional heat generated by such.

If you haven't read the article on the 6146 family of tubes that has been published in a number of amateur radio publications, it can be found at the following URL:

http://nebula.wsimg.com/e7364f5298b88b460a668216b4be5946?AccessKeyId=D1250C433DB440D6B60D&disposition=0&alloworigin=1


 Glen, K9STH 
Website: http://k9sth.net

      From: Bill Stewart <cwopr at embarqmail.com>
 To: boatanchors <boatanchors at mailman.qth.net>; eico <eico at mailman.qth.net> 
 Sent: Thursday, December 29, 2016 10:17 AM
 Subject: [Boatanchors] One Tuff 6146
   
I am replacing some pilot lamps and dusting out my Eico 720. Took out the 
final tube and noticed it has a fairly deep dimple which is surrounded with 
a black spot. The sunk in spot is probably a fat 1/16" deep. The depression 
area is just under the size of a dime...gradually rolls off into the deep spot. 
The tube is a Sylvania 6146/8298A. I'm sure I didn't run it that hard, but 
previously, it musta had a hard life. Final loading and output still where it 
should be. It's going back in....