TM 11-6625-3025-14/ET426-AA-MMA-010/E154 VII210/T.O. 33A1-8-902-1-1
(6) The 10 usec per division oscilloscope sweep rate is suggested for 675-line scan rate when observing
horizontal information.
(7) The 2 msec per division sweep rate is suggested to observe vertical information for all EIA Standard
scan rates and others which have a 60 Hz field rate. The 5 msec per division sweep rate is suggested
for vertical television formats having other than a 60 Hz field repetition rate. Be sure that more than a
full field is visible on the oscilloscope screen for proper vertical rate pulse inspections.
6-38. Signal Level Adjustments. The level of the video, blanking pedestal and sync portions of the composite video
signal output must be verified before inspecting pattern content. Black level, risetime and output impedance must be
checked as well. These tests can be conducted even though pattern proportions may not be adjusted to the exact value
required.
Amplitude and impedance have been outlined in EIA Standards. Television systems universally are at 75 ohm
cable impedance, at the following levels:
Video maximum level of 1.0v (including a blanking pedestal of 0.055v) plus sync of 0.4v,
making an overall composite video signal of 1.4v pk-pk.
This test sequence involves the following circuit cards (see figure FO-21):
Video .................................................................................................... Position 5C
Gray scale control .................................................................................Position 5B
Pulse input ............................................................................................ Position 2C
1
Connect the equipment for test as shown in figure 2-1. Set the oscilloscope sweep speed to 10 usec per
division.
2.
Connect the oscilloscope external sync to the H drive source. Sync the oscilloscope from the leading (-) edge
of H drive.
3. Connect the oscilloscope channel 1 input to the video G composite output connector, properly terminated.
Set channel 1 sensitivity at 0.5 per division.
4. Select the WINDOW function, VIDEO LEVEL at 10. Compare the oscilloscope display to figure 6-7a to
identify and check level of the video, blanking and sync portions of the signal.
6-30
