[R-390] 51J-3 PTO AGC Audio Fun

[David Wise]

> From: Tom M. [mailto:courir26@yahoo.com]
> 
> I went back in to the 51J-3 PTO this weekend after setting it 
> properly in 1996.
> 
> It was 4 kcs in the usual direction (I've been admonished for 
> calling it "long"
> so I'll refer to it as the "usual direction" from now on to 
> avoid confusion). 
> This was on 120V supply.

I hope I didn't come across as the Endpoint Terminology Police.
I only meant to express a preference, and I understand that
everyone's used to what they're used to.  I chuckled at
your coinage of "usual direction".  If we had a FAQ,
that would fit in just fine.  Maybe it should be
capitalized, like the Usual Suspects.
 
> This radio exhibits endpoint deltas with differing supply 
> voltages.  The OA2
> regulator is regulating, so I'm not sure if this is just my 
> radio, or a 51J-3
> thing.  

It's probably related to oscillator heater temperature.
We all know that the freq can drift if the temperature
changes.  It never occurred to me that the *spread* could
change, but it makes as much sense.  That puts the last
nail in the coffin of my attempt to linearize PTO warmup
by controlling heater current.  Speaking of which, I
suppose you could rig a filament regulator a la R-390A
Solid-State Ballast.

73,
Dave Wise