[R-390] R-390A power switch

[Roy Morgan]

On Jan 23, 2014, at 4:29 PM, Chris Farley <kc9ieq at yahoo.com> wrote:

> ...  Perhaps using a Y safety capacitor instead of a normal disc ceramic would be beneficial?

Good idea.  I will after a while make another order to justradios.com who sell these caps.  If that cap failed with the switch open, it would mean an amp of current through the 100 ohm resistor - smoke would come out for sure.

>  Inrush MOV's are good devices too,

I wonder if they make too much heat in the place they are often installed: near the fuse holder.

> but don't have the best reliability long-term.

Do they short or open up?

> Using a Triac to power the rig might also be a worthwile consideration,

Or even a relay.  There has been published a modification to the Collins S-Line 516F-2 Power supply to install a relay for the job.  The power switch is at the back of  a volume control in the transmitter itself, and is both failing due to the inrush overload and very hard to find.

Roy

Roy Morgan
RoyMorgan at alum.mit.edu
K1LKY Since 1958