William Mutch wrote:
I'm curious about what is invloved in converting boatanchor
(specifically my NC-125) power supplies from tubes to solid state bridge
rectifiers. I understand that most guys will mount the bridge and
dropping resistor on a tube socket so that the conversion is easily
reversable. How do you determine the difference between (a) the
voltage drop of the tube and the solid state bridge, and (b) the working
current so that you can calculate the appropriate values of the dropping
resistor and its power rating ??

One approach...

Often the increase in B+ is not enough to fret over. But if you want to
do it "right" its a simple matter of measuring the B+ with the tube and
then remeasuring with the ss rectifier to see how much you want to drop.
Start by using say a 100 ohm, coupla watt resistor and you can
calculate the current draw and then calculate a final value accordingly.

This also gives the advantage of KNOWING the ACTUAL B+ current draw
which may point you to other problems the set may have like leaky caps,
too much audio tube current draw, etc.-

-Bill