[R-390] Another (perhaps) silly ballast question

[Barry]

I got part of this mod finished this evening.  I ran a teflon-insulated,
20GA wire neatly from the IF deck plug to pin 5 of the ballast tube socket.
At first I thought this wasn't going to work because the compartments are
completely isolated from each other between where the plug is located and
the tube base; however, there is a very tiny opening where the sheet metal
was folded in just the right way to allow the wire to snake very neatly
beside the AGC amp and AGC detectors, beside the BFO and on to the tube
socket.  I ran the wire from the center tap through the plug on the IF deck
(even was able to snake the new wire inside the large boot where the rest of
the wires go into the plug and inserted a jumper between pins 5 and 7.  I
works great.

All I need to do is run the new wire through the plug on the PS.  Kind of a
pain when a resistor or appropriate tube will work, but I really wanted to
do away with the unnecessary heat source.

Regards,

Barry - N4BUQ

----- Original Message -----
From: "Barry" <n4buq at aol.com>
To: "R-390 HF Receiver List" <r-390 at mailman.qth.net>
Sent: Wednesday, January 04, 2006 3:13 PM
Subject: Re: [R-390] Another (perhaps) silly ballast question


> Well, I was going to wait until I tried it to make sure there weren't any
> "gotchas", but it appears someone else (Dan?) has mentioned this recently.
>
> I kept trying to think of a clever way to get 12.6VAC to the oscillator
> tubes -- even to the point of adding a filament transformer somewhere (it
> would be cheaper than a ballast tube costs these days and last longer) --
> when it occurred to me that if the 26.2VAC winding were center-tapped,
that
> voltage could be used.  That's when I looked at the schematic (and
confirmed
> on the unit) that the 26.2VAC winding is indeed center-tapped.  This tap
can
> be run through unused pins from the PS deck to the IF deck.  From the IF
> deck plug, I plan to run the wire to an unused pin on the ballast tube
> socket and plug in a jumper from that pin to pin 7.  This allows the
> original oscillator tubes to be used and if someone decides they want to
use
> a ballast tube, all that will be necessary is to unplug the jumper and
plug
> in the ballast tube.
>
> Barry - N4BUQ
>
>
> > Oh?  Well TELL us what the plan is!
> >
> > Roy
> >
> >
> >
> > - Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
> > 7130 Panorama Drive, Derwood MD 20855
> > Home: 301-330-8828 Cell 301-928-7794
> > Work: Voice: 301-975-3254,  Fax: 301-948-6213
> > roy.morgan at nist.gov --
>
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