[Elecraft] [OT] Grounding negative side of power supply?

[Jim Brown]

>Should the negative side of a power supply be connected to the supply  
>chassis (and thus to the "green wire" AC ground), or should it be left  
>floating? 

As Don says, it depends -- on what design mistakes the engineers made 
who designed the equipment. In other words, there can be a kind of "pin 
1 problem" for power wiring, where noise current flowing on power wiring 
(the black wire in a red/black pair) wanders around the circuit and 
causes mischief. 

The MOST important thing is that every chassis have a low impedance bond 
to every other chassis, so that leakage currents flow outside the 
chassis -- that is, green wire to green wire, chassis to chasssis -- and 
that the voltage difference between one chassis and another is small.  

Henry Ott has the fundamental answer -- figure out where the current is 
flowing by studying the invisible schematic hiding behind the "ground" 
symbol, and realize that there can be other current on that DC conductor 
besides DC. 

Remember -- low impedance means low resistance AND low inductance, and 
low inductance means SHORT and STRAIGHT. 

73,

Jim K9YC