Extron electronic VSC 150 Troubleshooting, Oscilloscope displays, Superimposed waveforms

Installation and Operation, cont’d

10. Check the display(s) for proper colors and for undesirable artifacts in the image(s). Make adjustments as necessary. Once the genlock timing has been adjusted, it should not require readjustment when changing to a new computer video signal input.

11. If other VSC 150s are part of this genlock daisy chain, connect the oscilloscope to each device, and repeat this procedure.

Oscilloscope displays

What you see on the oscilloscope while adjusting the

VSC 150 to match the genlock signal depends on the type of signal used, the type of oscilloscope, and the procedure the scope requires. This section shows some examples of oscilloscope displays.

The figure below shows the genlock input signal (top) and an out-of-alignment NTSC composite sync output signal (bottom) displayed on a waveform monitor to check for alignment. When the phases are aligned, the wave peaks on the bottom waveform should line up with those in the reference signal above it.

With this method there is no way to know if the signals are 180º out of phase. A delayed sweep on a time-based scope would allow a more accurate display of the input and output signal phase relationships.

Superimposed waveforms

A vectorscope is more accurate than a waveform monitor. The next figure shows an example of a vectorscope display when the horizontal phase is adjusted to align it with the burst (genlock) vector. Adjust the Horz Phase control until the difference between the two vectors is 0º. This example

shows black burst only (with no color). The burst vector is pointing to the left from the center.

350	0	10
340		20
330		30
320		40
310		50
300		60
290		70
280		80
270		90
260		100
250		110
240		120
230		130
220		140
210		150

200160

190 180 170

Vectorscope screen during horizontal phase adjustment

The figure below shows an example of a view of a vectorscope during adjustment of the color subcarrier phase (SC/H). The subcarrier phase should be aligned to 0º (indicated in the figure by the triangle).

350	0	10
340		20
330		30

A1+40	320		40
	310		50
	300		60
A2	290		70
	280		80
A3	270		90
	260		100
B1	250		110
	240		120
B2	230		130
-40	220		140
B3	210		150
	200		160
	190	180	170

Vectorscope screen during

color subcarrier phase adjustment

Troubleshooting

The image should appear properly on the screen(s).

If the image does not appear

1.	Ensure that all devices are plugged in.
2.	Make sure that each device is receiving power.
3.	Check the cabling, wiring and grounding, and make
	adjustments as needed. Ensure that the rear panel
	output selection toggle switch and PAL Out DIP switch

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