[R-390] Best ballast tube resistor

Tue, 13 May 2003 10:05:12 -0700

Bill ,  I don't know why you're re-hashing all these mod's again - they are
already available in the archives.  I was at a hamfest in Stanwood,  WA this
weekend and I was discussing the 390 reflector with a local  and he mentioned
that the participants "resonate" with one another.  I think it was a kind
compliment.  And from my short exposure,  I would say it's on the mark.  I
admire the continuity, humor and knowledge that comprise the tuned circuit of
this group.  I didn't see any 390's for sale,  only one SP 600Jx  for $250,  a
shop worn example. I came back with a spool of #40 magnet wire,  a book and a
meter.  I missed a free big chassis?? that had a large number of the good tube
shields still in place.   Dan.

Bill Smith wrote:

> That sounds like a great idea, Jim.  There are lots of tubes around, and so
> what if they don't quite operate at the right voltage as long as they
> operate ok.  You can probably also eliminate drift by adjusting your
> control.  I might try that on mine.  I don't have any space left on the
> front panel, so think I'll use a screwdriver slot type and won't need a
> knob.  It should fit just below the Line Meter switch.
>
> I couldn't find a right meter for my set, so I used a larger meter.  It is
> easier to read anyway.  I had to carve a little out of the washer underneath
> one of the handles, because the meter bezel bumped into it and
> unfortunately, the saw slipped when I was expanding the meter hole, so there
> is a little "air" on that side of the meter, but I used larger sheet metal
> screws and one of them holds it down real good.
>
> I didn't like the on-off switch, so I drilled another hole right above the
> frequency readout and put in a toggle switch.  Also, the calibrator isn't
> very good, and my PTO isn't very linear anyway, so I drilled another hole
> just below the function switch and mounted a rotary switch with 100kHz,
> 10Khz and 1Khz positions.   I put in a transistor crystal calibrator kit,
> mounted it right on back of the front panel.  It only took one screw to
> mount it.   A neat trick is to cut up a piece of innner-tube and put it
> under the circuit card so the parts don't make contact with the panel.  I
> tried using a flat-head screw to mount the card so it would look "original"
> but I don't think it was worth the effort, cause it is real easy to make the
> mounting hole too big.  Its hard get it just right anyway, but it holds ok.
> It shouldn't be too tight, or the card stops working.  I don't know why.
>
> The mechanical adjuster lets me tune to an exact zerobeat now on most of the
> dial, but sometimes I have trouble telling which zerobeat is which.
>
> Unfortunately, I can't turn off all of the calibrator, so some of the
> signals I hear in the radio have a squeel to them now.  But the dial light I
> put in the panel just below the bandwith switch looks great in the dark,
> even if it makes the set hum a little.  I made real short wire connections
> from the guts in the radio to the front panel, too.  They were a bear to
> attach from underneath but they finally made good contact.
>
> On the back, I didn't like the antinnna connectors, so I drilled holes and
> mounted a SO-239 plug and connected it right to the antenna coils.
> Something needs fine tuning, though, because the Antenna Trim adjstment
> doesn't seem to work anymore.  I'll have to try taking turns off the coils
> to see if that helps.
>
> I also mounted a T/R relay on the back.  There is a lot of room to mount
> whatever you want.  Be careful when you drill, though, because there are
> wire harnesses and parts right on the other side of the back panel.  I
> wonder why they made the set that way.  Gees, it is really easy to drill
> into something when you are making a hole.
>
> I've heard you can soup up the set with some more modern tubes, but I
> haven't found step-by-step instructions yet that I can follow to let me make
> the modifications.  I hope one of these days a good article will be
> published on Internet or in a magazine.  The radio works pretty well except
> on the higher frequencies and a preamp should help there.   Of course it
> would be better to modify the front end instead.
>
> Good luck with your radio.  What are you planning to do to it next?  I'm
> just about out of bare spots on mine.
>
> Bill
>
> ----- Original Message -----
> From: Jim Miller
> To: [email protected] ; [email protected]
> Sent: Monday, May 12, 2003 6:53 PM
> Subject: Re: [R-390] Best ballast tube resistor
>
> I drilled a 1/4 inch hole in my front panel to the right of the VU meter and
> installed a 15W wirewound pot.  I am able to adjust the pot for optimum
> operation of the oscillator tubes.  Since the changing filament voltage does
> cause a slight frequency shift, this can also double as a vernier tuning
> capability.  I am now working on calibrating the dial in Hz offset.  You
> must be very careful to avoid turning the pot to zero however, as it will
> fry the oscillator tube filaments.  I am thinking of using a sheet metal
> screw as a safety stop for this purpose.
>
> ----- Original Message -----
> From: <[email protected]>
> To: <[email protected]>
> Sent: Monday, May 12, 2003 9:29 PM
> Subject: [R-390] Best ballast tube resistor
>
> > Should I use a 39 or 40 ohm resistor to replace my bad ballast tube?
> >
> > 1%, 5% or 10% and what wattage?
> >
> > Someone told me that if I use a resistor, my R-390A would not work
> properly.
> >
> > What should I do?
> >
> >
> >
> > The Firebottle
> > The Original
> > Accept No Substitutes
> >
> >
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