[Hallicrafters] More on solid state rectifiers

[Craig Roberts]

Hi again,

On the topic of possibly damaging inrush currents being unleashed when 
substituting solid state devices for tube rectifiers, here's when Ted 
Weber himself -- maker of the luxurious Weber Copper Cap -- said a few 
months ago. He's talking specifically about using them in Collins 516F-2 
power supplies, but the same principle applies elsewhere.

73,

Craig
W3CRR

Ted says:

"The tube rectifier has around 8 seconds of warm up time. Since the 
internal
resistance of the tube is high until the tube is warmed up, the B+ rises
slowly as it charges the HV filters. At that same time, the other tubes are
also warming up. When they get up to temperature, they provide a load that
drops the B+.
So, the long delay of the rectifier warmup prevents a high voltage B+
condition on the other tubes in the rig until they warm up. Our copper caps
have an inrush themistor that has a negative temperature coefficient, 
and as
the B+ current increases, its internal resistance decreases. Hence, it 
has a
warmup time like the tube rectifier. However, the warm up time of our 
Copper
Cap is only about 1-1/2 to 2 seconds, depending on the current draw as the
filters charge. Bottom line is, with the C-Cap, the B+ might ramp up higher
than some may be comfortable with until the other tubes warm up and pull 
the
B+ back down to normal operating level."