User Manual

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KRAMER ELECTRONICS LTD. 12
11.3 Video Signal
(VM-80V, VM-10AN)
Problem Remedy
No video at the output
device, regardless of
input selected
1. Confirm that your sources and output device are turned on and connected
properly. Video signals connected to the input of your amplifier should be of an
identical signal format at the output of your source. Video signals at the output
of your amplifier should be of an identical signal format as at the input of your
display or recorder.
2. Confirm that any other amplifiers in the signal path have the proper input and/or
output selected.
3. Use the Video Tester to test the video path leading to/from your amplifier (see
section 4.1 " Video Tester")
Video level is too high
or too low
1. The amplifiers in this manual have termination switches on each input. Verify
that the video line is well interfaced through 75ohm impedance; otherwise it
results in a video level that is too high or too low. Check if looping is used and if
termination switch is in the proper position for this state.
2. Confirm that the connecting cables are of high quality, properly built and
terminated with 75ohm BNC connectors. Check level controls located on your
source input device or output device.
3. Adjust (VM-80V), only if necessary, video output levels using the front panel
trimmers. Bear in mind that the machine was fine-tuned at the factory for
transparent operation, and unnecessarily adjusting the trimmers will upset this
transparency.
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. Passing that voltage difference
through any available interconnection, including your video cables, compensates
this difference.
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.
2. Remove equipment connected to this 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.