[Elecraft] New KX3 reverse voltage smoke

[David Woolley]

I'd definitely expect the chassis ground to have a low impedance 
connection to the negative power supply rail, and normally that would be 
a DC connection.  Without it the screening of internal circuitry would 
be less effective.

The K2 definitely has a DC path from supply negative to the case.

I'd also expect any power supply large enough to require a ground 
connection, and eventually have exposed voltage output rails, to have 
ground connected to one.  Without that, capacitive leakage can generate 
a significant electric shock hazard, or even cause damage when the 
powered equipment is being interconnected with equipment on another 
power supply.

If the safety earth rises significantly above that of other conducting 
items during a fault, there is a defect in earth bonding in the 
installation as a whole, that needs urgent rectification.

-- 
David Woolley
Owner K2 06123.

On 05/09/2020 19:32, Alan - G4GNX wrote:
> I don't understand why the antenna being connected provided a path to 
> ground for the supply.
> 
> If that really is the case, there would seem to be a fault with your 
> power supply. The secondary (low voltage) side of a PSU should never be 
> connected to ground. Both poles should always 'float'.
> 
> I'd be very surprised if Elecraft had connected the negative supply to 
> chassis ground inside the KX3 either.