[Boatanchors] TCS dry disc rectifiers

[w8au at sssnet.com]

At 12:25 PM 8/25/2016, WA5CAB--- via Boatanchors wrote:

>what you should replace without bothering to determine whether or
>not it is still working is the dry disc 12VDC supply rectifier. It may be
>copper oxide, in which case it may still work. Or it may be selenium in which
>case it most likely does not, or if it appears to work, you aren't yet
>seeing the characteristic decline of front to back ratio and the increase in
>forward resistance.

Robert:  Just going over my GRC-9 which contains a selenium 
rectifier.  I thought
about replacing it with silicon, but wanted to learn more about it first.  The
GRC-8 manual gives no info except for a single statement in the circuit
analysis.  Nothing in the parts list. Turns out it is hooked up as a 
3.6 volt shunt
regulator for the TX 3V filaments. :-[

I haven't returned to the bench today to actually measure that fil voltage buss
but curious about the application.  Did the seleniums have a Zener effect
in reverse mode?    Would this predate Mr. Zener's early fifties invention?

Perry   w8au