Kramer Electronics VM-3Sxl - Manual (Page 12)

11
KRAMER ELECTRONICS LTD.
Problem Remedy
Noise bars "roll" up or
down in the output image
or:
Low frequency hum in the
output signal
Hum bars (ground loop) are caused by a difference in the ground potential of any
two or more devices connected to your signal path. This difference is
compensated by passing that voltage difference through any available
interconnection, including your video cables.
WARNING!
Do not disconnect the ground from any piece of video
equipment in your signal path!
Check the following to remove hum bars:
1. Confirm that all interconnected equipment is connected to the same phase of
power, if possible.
2. Remove equipment connected to the phase that may be introducing noise,
such as motors, generators, etc.
3. Disconnect all cables and reconnect them one at a time until ground loop
reappears. Disconnect the affected cable and replace, or insert an isolation
device (opto isolator or transformer) in the signal path.