Dolby
®
Model CP650 Installation Manual
Maintenance and Troubleshooting
9-3
Alignment
Warning: Class 2 LED Product per EN 60825-1:1996. Do not stare into
the red LED beam. Do not attempt to view the LED beam with any type of
optical device.
1. Connect an oscilloscope (20 MHz minimum bandwidth) to test points on the setup
control panel. Some digital oscilloscopes may not be usable for this procedure
even though they may have the required bandwidth.
a. Ensure that the probes are 1X and connect scope Channel 1 to the “Video” test
point. Connect only this probe's ground to the ground test point.
b. Connect scope Channel 2 to the “Clamp” test point.
Mic Bypass
Video Clamp
Ch 1
Ch 2
GND
RTA1 RTA2
1 2 3
7
4 5 6
8
SIGNAL
PRESENT
Lt
Rt
Lt
Rt
Oscilloscope
c. Set both channel vertical input sensitivity controls to 1 V/div, DC coupling.
Set the vernier to calibrated (usually the inner knob—rotate until it “clicks”).
d. Set horizontal sweep rate to 2 µs/div.
e. Set the trigger source to Channel 2 and positive polarity.
f. Turn on power to the digital soundhead and the CP650.
2. Set the oscilloscope display.
a. Thread and play a Cat. No. 69T Dolby tone test film loop.
b. Display only Channel 2, and adjust trigger level to lock onto the clamp signal.
c. Adjust horizontal position to line up inside edge of left clamp signal with left
screen graticule.
d. Adjust the timebase sweep vernier to line up the inside edge of right clamp
signal with right screen graticule.
e. Select Channel 1 display.
f. Temporarily switch the scope channel 1 input (video) to GND and adjust the
vertical position to coincide with a horizontal screen graticule. This is the 0 V
reference baseline.
