[R-390] Selenium Rectifier

[Barry Hauser]

Hi Don & gang

Seems to be general knowledge, perhaps peppered with some urban (plus 
suburban and rural) legend, that selenium rectifiers often fail.  Some of 
this, no doubt is because the last ones were made sooooo long ago.  Failure 
modes include sudden death with acrid, noxious fumes, or slow deterioration, 
and I suppose, going open as K2CBY reported.  For example, it's SOP to 
bypass them with an individual rectifier and dropping resistor in tube 
Transoceanics.  In those radios, they tend to develop higher resistence with 
age and affect performance, well before they go up in smoke. (That said, 
most of my T/O's are running on the finned wonders, but I don't run them 
unattended.)   There are a couple of non-finned ones in AN/GRR-5's which 
tend to fail, including the one built into the cabinet, though I think 
that's a copper oxide rectifier.

The thing is -- with so much pre-emptive replacement, it throws the stats 
off, so we will never know just how many fail in what mode by when.  And as 
far as those that fail in catastrophic noxious gas mode ... have we heard 
from K2CBY .. lately? ;-)

Only the Shadow knows ...

Barry


>I don't recall anyone ever reporting a catastrophic failure of this
> rectifier.  Anyone?
>
> About two years listmember K2CBY posted this:
> -----
> I had the selenium rectifier fail one leg to open on my Motorola Contract
> 363-PH-54 chassis about 10 years ago. No short, no smoke, no smell. The
> symptom was a very loud buzz from the antenna relay and a failure to pull 
> in
> completely when the FUNCTION was switched to CAL. I assume the same 
> symptom
> would appear if BREAK IN was enabled and the ptt line grounded. The 
> symptoms
> of a failed selenium rectifier are so obvious and it is so easy to get to
> that I wouldn't bother with pre-emptive replacement.
> Miles, K2CBY, Sag Harbor, NY
> -----
>
> Anyway, along with not eating R-390 meters (ala Roy Morgan), you shouldn't
> be grinding up used selenium rectifiers as dietary supplements (ala Barry
> Hauser).
>
> Don
>
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