[R-390] A few SP-600 questions

[Barry Hauser]

Jack wrote:
> Is the stock power plug a readily available item? Mine came
> with a line cord running through one of the vent holes on the chassis
> and the power receptacle well taped up.

They vary.  A lot of them have a regular strain relief on the left side of
the rear panel.  Some may have a round 3-pin Navy style connector.  Not sure
what power receptacle you mean (that's taped up). Some may have one of two
early generic equipment connectors -- forerunners of the PC/office equipment
type that's now standard.  One is just a pair of flat blades that will fit a
cut down single socket extention cord.  Another type has the curved,
twist-to-lock prongs.  There were two prong and a grounded version of those
with a center pin.  Not sure where to get those anymore.  But, I'm guessing
as to what you have there.  Take off the tape and take a peek.

>
> How stable should the local oscillator  be on 6 meters?  I can tune SSB
> on 27 mcs with good stability, but the local 6 meter beacon
> warbles all over the place. SSB would be impossible to tune,
> the short term stability is just too bad.  Is this normal, or
> do I have a problem to solve?

Someone else will have to answer.  My take is that the high end freq. range
on these was a bit of a reach, but may be possible to tweak up with
component replacement and maybe some tube swapping.

When you checked for tubular caps, did you look inside the turret and under
the RF strip?  There are also caps hiding in the IF transformer cans.
Chances are all are disk ceramics, but, if you don't look, don't assume.
Also, prevously considered "good forever" silver mica caps have been
reported as troublesome here and there -- I guess the 50 year warranty ran
out.

BTW -- How much warmup did you allow? Probably needs a good hour.
>
> Is the stock antenna connector supposed to be an
> SO-239?  Mine looks like it has been replaced.

In almost all cases, this is an SO-239 mounted at the rear of the RF strip
facing up.  Very often, there is (should be) an elbow connector on it so the
connection faces rear instead of straight up.  Originals tended to be silver
plated, so may be tarnished black now.  If it's bright and shiny, it may
have been replaced by previous owner or depot with a non-tarnishing type.

>
> Tried to see if there is an SP-600 group on qth.net, but
> that page is loading super slowly today.

There is no SP-600 group as such, but there is a Hammarlund list, which is
not limited to SP-600's.  However, most of the SP-600 people are here too,
and it's one OT subject that's highly tolerated here.  The SP-600 is the
official antidote for R-390 Wrist-itis, for those who forget themselves and
try to band cruise the '390.  A few spins of the highly flywheeled SP-600
will unravel the kinks in the wrist and elbow.  More effective as a
preventative -- bandcruise on the SP-600, like it?  Lock it in on the '390.
Want to "channel surf"?  Turn down the audio on the '390, go back to the
SP-600.

Barry




>
> Thanks
> Jack Antonio WA7DIA
> scr287 at sbcglobal.net
>
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