Thread: Ground Loop
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Scott Dorsey Scott Dorsey is offline
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Default Ground Loop

Bob Simon wrote:
My Panasonic TV (TH-50PH9UK) is a video monitor only; all audio is routed t=
hrough my NAD preamp and amp. Last week, a hum started without having made=
any changes to any systems. Today, I tried unsuccessfully to eliminated i=
t by plugging the TV into the same power strip that the preamp and amp are =
plugged into. Lifting the TV's ground eliminated the hum.


The TV has multiple grounds. That's the problem. Likely what you mean is
"lifting the TV's power line safety ground."

Does this suggest that a capacitor shorted last week in the amp, preamp, or=
TV?


No, it suggests that the grounding system on the cable TV line has likely
changed, since this is the most common source of these problems.

As a practical matter, have I created an unsafe or inappropriate condition =
by lifting the TV's ground pin?


Yes, totally. They don't call it a "safety ground" for nothing. Isolate
the ground on the cable TV line, not on the power line.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."