Kramer Electronics VM-1042 - Manual (Page 19)

KRAMER ELECTRONICS LTD.
17
WARNING!
1. The amplifier was calibrated at the factory for
transparent operation at 1 meter. Any re-tuning will
upset amplifier’s transparency.
2. Do not attempt to adjust the Equalization trimmers
without using accompanying standard calibrated
oscilloscope or waveform monitor!
Coupling
The coupling function enables the operator to determine whether the incoming video signal
is DC or AC coupled. When DC coupling is selected and proper standard video signal is
applied to the amplifier’ s input, the output signal is equal to the input signal. When AC
coupling is selected, DC components of the incoming signal are removed. DC coupling is
always preferable since AC coupling might cause some linearity distortions in low and
high frequencies (due to non-ideal behavior of capacitors). A problem may arise when the
incoming signal is riding on a DC offset especially when the acceptors are highly effected
by deviation of DC offsets (A/D converters for example), which in turn results in a
distorted picture.
Black Level Clamping
(VM-1015, VM-1021 only)
In the Black Level Clamping process, the incoming black level signal is "clamped" to
"zero". Whenever this process is activated (by pressing the "BLACK" pushbutton), the
amplifier’ s internal system automatically switches to AC coupling, thus removing the
original DC components of the incoming signal. The black level is clamped to "zero", thus
converting the input signal to a standard video signal. Whenever the picture is distorted,
too dark or too bright the DC offset is probably responsible so it is recommended to choose
AC coupling. If the malfunction still exists, the "BLACK" pushbutton should be activated
to restore the standard DC level of the video signal.
Sync Tip Clamping
(VM-1015, VM-1021 only)
Sync Tip Clamping is recommended for video signals such as RGB. The RGB signal
maximum amplitude is between 0.7V DC to 1V DC and their bottom level should be
always clamped to "zero". It sometimes contains sync signal ("sync on green") and
sometimes does not. When the Sync Tip Clamping process is activated (by pressing the
"Sync Tip" pushbutton), signal bottom level is clamped to "zero" and the whole video
signal is now positive and "zero" clamped.
TAKING CARE OF YOUR VIDEO AMPLIFIER
Do not locate your amplifier in an environment where it is susceptible to dust or moisture.
These may damage the electronics, and cause erratic operation or failure. Do not locate
your amplifier where temperature and humidity may be excessive. Do not clean your
amplifier with abrasives or strong cleaners. Doing so may remove or damage the finish, or
may allow moisture to build up. Take care not to allow dust or particles to build up inside
unused or open connectors.