[AMRadio] Solid State 575 mercury vapor RectifierReplacementsneeded


Jim Wilhite w5jo at brightok.net
Sun Oct 4 11:40:48 EDT 2009


Steve,

What kind of resistor do you use in this type of rectifier build to 
simulate the voltage drop?

Jim/W5JO


----- Original Message ----- 

> I've made my own solid-state plug-in replacement rectifiers for a
> variety of tube types.  I look up the tube specs and select 
> solid-state
> diodes that stack up appropriately for current and forward and reverse
> voltages. I usually end up using either 1N4007s or 1N5408s.  From
> on-lline sources like Digikey or Mouser or All Electronics the diodes
> are very inexpensive, ten cents to maybe 30 cents each.
>
> I put the diodes on a rectangular piece of perfboard sized to fit
> upright with its bottom end tucked within the sides of the base of the
> defunct tube it is replacing.  A small L bracket holds it in place.
>
> If you use diodes from the same "run" (which is easy if they are sold
> on the paper tapes used by manufacturers today) then I find no
> equalizing components are needed.  I add a few more diodes than the
> calculated voltage required for an extra measure of safety and have
> never had a failure, even in broadcast rigs on the air 24/7 with lots
> of lightning and power bumps to deal with.
>
> You can expect somewhat higher voltage from the new stack than the
> original tube rectifier - if that is a problem for the rig, then add a
> series power resistor to simulate the internal voltage drop of the
> earlier tube.  So far I've only needed to do that once when the new
> higher B+ exceeded the rating of the by-pass caps in the other 
> sections
> of the rig.  Otherwise the rigs seemed to thrive on the higher 
> voltage.
>
> Steve WD8DAS



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