[Hammarlund] HX-50 VFO Wobble

[Kenneth G. Gordon]

On 20 Nov 2014 at 18:57, Bill Stewart wrote:

> I have changed the VFO tube...6AU6 (V105) and replaced a few O/T resistors
> around the VFO tube. I re-heated solder joints around the VFO. Tried to polish
> the VFO capacitor wiper and de-ox'ed it. Also de-ox'ed the 6AU6 tube socket. 

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