14 – Calibration
VLM-40 NTSC T
ECHNICAL
I
NSTRUCTION
M
ANUAL
CALIBRATION
NTSC C
ALIBRATION
...
The VLM-40 has been carefully calibrated for NTSC operation
at the factory. However, the procedure is listed here for your
future use.
NOTE: The VLM-40 is only as accurate as the waveform generator
you are using. Check sync and raster amplitudes before beginning
calibration.
1. With the power off, remove the bottom four screws and lift
off the enclosure to expose the circuit board, as shown in
Fig. 17 (on the next page).
2. Connect a waveform generator to the VLM-40 video input
and turn on the termination switch, SW1. Set the waveform
generator to split-field bar pattern (100% white flag).
3. Apply power to the VLM-40. Adjust the rear panel input
level control VR 13 so that the 100 IRE peak dot LED is lit.
Verify that the -40 IRE sync amplitude LED is lit.
4. Select the full-field white raster waveform (100% white) on
the generator. On the main board, adjust the average
calibration control VR 36 so that the 100 IRE average bar
LED is lit.
5. Select the stairstep waveform on the generator. Verify that
the set-up LED on the VLM-40 is now lit red, indicating a
set-up violation.
6. Disconnect the waveform generator from the VLM-40.
Verify that both the sync and set-up error LEDs are red, and
that the main display is blanked.
7. Turn off power and reassemble the unit.
