[R-390] R-390A -relay problems

[Miles B. Anderson, K2CBY]

The fact that the antenna relay pulls in after warmup is not unusual even
though the selenium bridge recifier is starting to fail in the open mode.
The filament current load drops considerably as the tubes warm up. Once the
heater current stabilizes, the voltage on all of the power transformer
secondaries (including the 26 volt winding that drives the antenna
changeover relay) goes up. This is true even without inrush protection.

I use a CL-80 thermistor for inrush current protection and have never had a
problem with relay buzz -- but then I've used a silicon diode bridge to
rectify the antenna relay AC for the past 15 years -- ever since the
selenium rectifier made a loud buzzing noise and failed open.

Miles Anderson, K2CBY
k2cby at optonline.net