[R-390] Selenium rectifiers

[Don Reaves]

Less than a half dozen folks reported actual real-time failures with noxious
odors of their antenna relay rectifier stacks.  Most who reported broken
units indicated they had failed open; no bad stuff.  Still, it could happen
but its not a foregone conclusion they are going to fail catastrophically.
These parts are mil-spec, not the consumer grade stuff we had so many bad
experiences with in early tube gear.  As to whether they are selenium or
copper oxide, the parts list (R-389 manual) specifies: Rectifier, Metallic,
27V, Selenium.  

I asked this question because I have one of the R-391 matching 28V power
supplies, PP-629.  It has a beautiful selenium rectifier stack in it about
the size of a loaf of bread.  I'm going to leave it alone and use it as is.
It's job is to run the autotune circuits in the R-391.  

My elmer used to call these things rectum finders.  I suppose there was some
double meaning to that term based on their failure modes, but as a kid I
knew not.

<grin>

Don