[AMRadio] Oscillator Filament Voltage change and frequency drift


Jim Candela jcandela at prodigy.net
Fri May 12 10:27:12 EDT 2006


Don K4KYV said:
> > 
> > I ran the VF-1 off a CVT.  It too, drifted with
> slight 
> > changes in fil. 
> > voltage.  I think both the VF-1 and Collins PTO's
> use a 6AU6 
> > as oscillator 
> > tube.  My "silent" Sola beats fooling around
> swapping tubes.  
> > I suspect even 
> > a good tube would eventually become drifty with
> age.
> > 
> > Don k4kyv


Don,
   
 I'm wondering about those 6AU6's. Not all of us have
a Sola CVT, so I have another idea. Change the tube
for a 5AU6, and then take the 6.3 vac (usually
unbalanced), and 1/2 wave rectify with a low drop
Schotcky diode (about 0.3 volt forward drop), filter,
and then run through a 3 terminal low drop 5 volt
regulator. I'll do some book searching for some
suitable part numbers. I think it will work with
minimal fuss. Some of the available low drop
regulators (use pnp output transistor)only need about
1/2 volt minimum in/out differential to maintain
regulation, so the trick will be to keep the regulator
Vin at the 60 hz ripple minimum value at > 5.5 volts.
This will require a big filter capacitor in value, but
5,000 mfd at 10 volts is still real small in size.

Jim
JKO



More information about the AMRadio mailing list

This page last updated 21 Oct 2017.