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KRAMER ELECTRONICS LTD.
21
Problem Remedy
Noise bars are “rolling” 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 that phase that may
introduce noise, such as motors, generators, etc.
3. Disconnect all interconnect cables and reconnect them
one at a time until ground loop reappears. Disconnect the
affected cable and replace, or insert an isolation
transformer in the signal path.
14.3 Audio Signal
Problem Remedy
No audio at the output device,
regardless of input selected
1. Confirm that your sources and output device are powered on and connected
properly. Audio signals connected to the input of your switcher should be properly
wired to the output of your source. Audio signals connected to output of your
switcher should be properly wired to the input of your switcher or recorder.
2. Confirm that any other switchers in the signal path have the proper input and/or
output selected. Pay special attention to input switchers that may be built into your
switcher or recording device.
Audio level is too low
1. Confirm that the connecting cables are of high quality and properly built. Take
special care in noting the wiring configuration of balanced to unbalanced cables.
2. Check level controls located on your source input device or output display or
recorder.
The switcher switches the
video but does not switch the
audio.
One of the audio cables leading to the main board is disconnected and cannot transfer
the switch command to the video.
The switcher will not switch
via the RS-485 control
The RS-485 control is fed by a flat cable from the upper audio board to a socket on
the main board. One of its connectors may be disconnected.
Turn OFF the mains switch, remove the power cord from the mains socket and
carefully remove the cover of the switcher. Verify that all the flat cables from the
main board to the control board, from the audio board to the main board and from the
switchboard to the main board are undamaged and properly connected.
NOTE
Sometimes connectors work loose and have to be reinserted.
(Perform this firmly but with care).