On 3/21/2011 7:57 PM, Christopher E. Brown wrote:
> The green wire in the AC cable bonds the the inside of the steel chassis
> and the circuit board, the chassis bond is on the outside. Bonding the
> outside lug to the same gnd as the power plug corrected things for me.
I find the description a bit confusing, BUT -- I suspect a problem with
PAINT preventing an electrical contact between the green wire and the
chassis. The inside of the chassis and the outside of the chassis
SHOULD be the same point. Further, the green wire in the AC cable MUST,
by law, go to the chassis.
There CAN be magnetic coupling of noise from a switching power supply to
the outside world, but that is NOT what gets fixed with the ground lug.
In general, it is NOT a good thing to bond V- to the chassis of the
power supply. The reason is that doing so can couple the IR drop on the
V- lead to accessory equipment that is powered from same supply. When
running SSB that IR drop will sound like SSB detected by an AM
detector, which in turn will show up as distortion in the transmitted
signal. Bonding V- to the chassis also can couple buzz from power line
leakage currents to the audio signal.
If I were you, I would carefully scrape the chassis at the point where
the green wire connects to make sure it is making good contact, but I
would remove any connection between V- and the chassis.
73, Jim K9YC
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