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
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