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

[Tom M.]

Gentlemen?

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.

One turn of the endpoint screw remedied the 4kcs endpoint problem exactly (I'll
tell you tomorrow what the new endpoint error is after it drifts overnight).

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.  

I also slowed down the AGC (thanks group for the tips) by jumping the .1 uF
C205B with an additional .5 uF to ground.  This slowed the AGC down, and the S
meter no longer pegs upon switch-on (but when going from stand by to on, I get
an alarming arc in the on/off switch!! Yikes, what is that?  Charging of the
new caps?).

Also did an audio mod by uping coupling caps C209 and C211 from .01 to .1 uF.

C209 is behind the front panel, which I had access to from the PTO work, but
otherwise this would be a P.I.T.A. to change.

Audio is a little better.

In all, fun work on the 390's light weight brother.  The 51J is a fine receiver
IMHO.

73 Tom N5OFF

__________________________________________________
Do You Yahoo!?
Yahoo! Tax Center - online filing with TurboTax
http://taxes.yahoo.com/