[R-390] Best ballast tube resistor

[John Kolb]

On Mon, 12 May 2003, Bill Smith wrote:

> 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
>
> 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.

I thought about doing that the the xtal calibrator, but found it was
a lot easier to just take out the speedometer dial and replace it
with a solid state frequency counter. Never have any more of those
zero beat problems.

>
> 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.

Kinda hard to find enough transistors to replace all those tubes,
What you need is to get some of the IC thingies that have lots
of transistors inside them.

John