[R-390] Resistors for the R-390A and beginner help

[Bob Camp]

Hi,

One important point about the carbon composition resistors - they never were
in tolerance !!!!

It turns out that in order to properly check a carbon composition resistor
you have to "stabilize it's moisture content". This used to involve baking
them in an oven for a while to dry them out. This would tend to increase
their resistance. If you left them in the oven to long they went out of
tolerance on the high side.

The radio was designed with this kind of behavior in mind. The guys at
Collins didn't know everything but they certainly knew about carbon
composition resistors. I just wish they had figured out PTO's about three
years earlier .... another story.

Any way except for the cathode bias resistors just about every resistor in
the radio will do just fine at 1.5X it's original value. A lot of the
resistors will do fine at 2X the marked value. It's not worth changing them
out unless there is a voltage off somewhere in the radio. Simply changing
out every resistor that measures more than 10% off from marked value is a
good way to ruin a radio. You will do more damage to the radio than the
improvement you will get from fixing something that isn't broken.

Huff, puff. Hard to stomp and shout so much late in the evening .....

    Take Care!

        Bob Camp
        KB8TQ