[Milsurplus] DY-105/GRC-9X Relay K3

[WA5CAB at cs.com]

Actually, the deterioration mode of aged seleniums is that the front to back 
ratio tends to 1:1 and you are left with a resistor of several tens to several 
hundreds of ohms.  What happens next depends upon the circuit it's in.  
Response time of ballast tubes is a few seconds, not many minutes.  Unless you have 
no ballast tubes the simplest solution both electrically and mechanically is 
to replace the seleniums with a silicon equivalent.  You can pull the stud 
through the selenium out and insert common stud mounted diode insulating washer 
or washers.  Then use the selenium terminals for mounting the silicon diode or 
diodes.

In a message dated 9/3/2008 9:26:38 PM Central Daylight Time, 
brunneraa1p at comcast.net writes: 
> In the transmitter the 3A4's are fed by a dropping resistor from the 6.3 
> volt line, and regulated by a selenium rectifier.  After 60 years the selenium 
> rectifier is probably non-conductive in both directions, giving no 
> regulation.  The solution is to put the ballast tubes in a safe place, and provide 
> regulated voltages to the 2E22 and 3A4 tubes.
> 

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480   
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