[TenTec] Model 963 questions

[Don Allen]

I have two Astron RS-35M supplies, one purchased about 12 years ago, and 
the other about 6 months ago.  One constant discussion on this supply's 
design is "to chassis ground or not to chassis ground" the 13.8VDC 
negative output line.  Some RS-35's have the negative line tied to 
chassis ground, e.g. the AC line's green chassis ground wire through a 
inside jumper or pig-tail lead, others do not.  This was a running 
production change at some point in time.  And here's where the 
discussions begin... an example of this discussion can be found here: 
http://www.repeater-builder.com/astron/astron-index.html

Repeater-Builder.com says specifically not to tie the output's negative 
line to chassis electrical ground, due to the creation of ground loops.  
Astron says to tie the negative line to chassis ground to eliminate the 
possibility of RF getting into the supply.  This discussion has gone on 
literally for years.

The jumper from the negative output line or post to ground is simply a 
wire jumper from the negative post to the bottom of the chassis or 
cabinet through a machine screw with an external tooth lock washer and 
nut.  Due to the thickness of the cabinet's paint, this external tooth 
lockwasher may or may not provide a good chassis ground.  Also, the 
Astron RS supply's chassis' top, sometimes electrically floats, as the 
screws often do not make contact with the bottom of the chassis or 
cabinet due to paint at each contact point for each screw.

Some of my best friends who've been in EE for decades even differ on 
whether or not to ground the 13.8VDC output negative lead.  And, Astron 
does not seem to be consistent, as I just purchased a SL-11A slimline 
11A linear supply, and its 13.8VDC negative lead is _not_ tied to 
chassis electrical ground.

73
Don W9CW