B&K Precision 1249B - Manual - Manual (Page 26)

26
OPERATING INSTRUCTIONS (CONT.)
scan. It is not compatible with high resolution graphics monitors
which use special high frequency scan rates.
Some color monitors accept either composite video signals or
RGB signals. Often, positive polarity vertical and horizontal sync
is required in RGB monitors. Some RGB monitors use low level
RGB signals and vary color saturation in response to analog
changes of the signal level. Others use higher TTL level excitation
and display only fully saturated colors- The Model 1249B NTSC
Generator provides signals for most versions.
Separate R, G, and B outputs with selectable TTL or LOW
level are available at BNC connectors on the front panel. In
addition, positive polarity Vs (vertical sync) and Hs (horizontal
sync) are available at additional BNC connectors, also on the front
panel. To simplify connections, a 9-pin connector (sub-miniature
D-type) is provided which mates with the 9-pin connector used on
the most common RGB monitor configuration (the connector is
IBM PC compatible). This duplicates the functions of the R, G, B
Vs, and Hs jacks in one connector so that all connections are
made simultaneously with a single cable.
The procedure for using the RGB outputs is as follows:
1.
Connect the RGB outputs of the NTSC Generator to the
inputs of the color monitor.
a.
Connect the R, G, and B outputs of the Generator to the
corresponding red, green, and blue inputs of the color
monitor.
b. If composite sync is required, connect the
COMPOSITE SYNC output of the Generator to the
sync input of the monitor.
c. If separate vertical and horizontal positive polarity sync is
required connect the Vs and Hs outputs of the generator to
the corresponding vertical and horizontal sync inputs of the
monitor.
d. If the color monitor is equipped with a 9-pin connector that
mates with the RGB receptacle on the Generator, connect it.
All necessary connections are made simultaneously.
2.
Select TTL or LOW level as appropriate for the monitor
being tested.
3.
Select the desired pattern.
WAVEFORM MONITORING
It is often desirable to examine the waveform on an oscilloscope
or waveform monitor. For example, in troubleshooting a television
receiver, the COMPOSITE VIDEO output may be applied to an
oscilloscope or waveform monitor and the waveform used for
reference. Meanwhile, the rf or i-f output which is modulated with
the same waveform may be applied at various points in the equipment
under test. The waveform measured at the video detector of the unit
under test may be compared to the reference waveform generated by
the NTSC Generator. Degradation of the waveform indicates poor
circuit performance or misadjustment. A dual trace oscilloscope is
very handy for such wave-form comparison.
1. Connect a coaxial cable from the COMPOSITE VIDEO
output jack to the vertical input of the oscilloscope.
Terminate into 75
Ω.