[Hammarlund] HX-50 VFO Wobble

[Glen Zook via Hammarlund]

EKB beat me to to it!  The 6AH6 generally works considerably better than the 6AU6 as an oscillator.  The tube is a direct substitute.  That is "plug and play".  The only thing is that, because of slightly different inter-electrode capacitance, any frequency calibration may have to be "touched up" slightly. Glen, K9STH

Website: http://k9sth.net
      From: Kenneth G. Gordon <kgordon2006 at frontier.com>

6AU6s are somewhat problematic: their quality varies a lot.

My advice is to replace that 6AU6 with a 6AH6WA or the military numbered 
equivalent, the 6485.

I routinely use 6AH6s in every oscillator circuit that would normally use a 
6AU6 since I discovered a long time ago that the 6AH6WA when used in a 
VFO works much better.

Also, if you use a 6AH6WA, you can reduce the plate voltage from the 
normal 150 VDC to 108 VDC, thereby reducing heat, drift, and chirp.

Ken W7EKB