[Heathkit] DX-60B Function Switch

[Mark K3MSB]

For the 260V secondary that gets switched by the function switch.....

A relay is the best solution,  but why hasn't anybody just put in a 3 ohm
inrush current limiting resistor just before the voltage doubler diodes?

The manual says to load the radio to 150 mA.   Let's double that to 300 mA
for the following:  0.3x0.3x3 ohms = 0.27 W,  so a 3 ohm 5W resistor is
overkill, and very small.

Putting in such a resistor in the 117V primary is a bit harder, but parts
are readily available.  Let's say 3 A.  3x3x5 ohms = 45 W,  but one can
drop the resistance and 3 A is being liberal according to the specs in the
manual.

Is it the voltage that kills the switch, or the current?   Each time that
switch is closed for the HV,  you're going into a filter cap bank that may
very well be drained (nasty stuff at those switch contacts...)

As I said, relays are the way to go, but I'm curious why I've never seen
the Inrush current solution used.

73

Mark K3MSB