[Boatanchors] Identity of plugin solid state rectifier replacement

[Drew P.]

Brian wrote:
 
> The 5R4 has much lower rectification efficiency than
> solid-state diodes. Consequently, the output Voltage will be
> higher. The commutation efficiency of solid-state diodes is
> higher than the 5R4 - so, there will be rectification
> spikes. Suggested solutions to these - put about 100 pF
> (experiment) across the diodes and put suitable resistors in
> series with the transformer windings.

It would seem that in some applications the higher voltage output capability could be used to advantage.  I've seen it "recommended" for the Hammarlund SP-600 to change the 5R4 over to solid state, and then to remove the input filter capacitor after the rectifier, thereby changing the filtering scheme to choke input.  Apparently the "gain" due to solid state rectification is neatly offset by the "loss" due to conversion to choke input, giving the correct output voltage.

The SP-600 filter scheme normally is capacitor input and uses 3 caps interspersed with 2 chokes.  Don't know how well the "suggested" modification would work with the now-input choke not being of the swinging type.

Drew