9. Change the TIME/DIV to MNL, deactivate VIEW
A/VIEW B, reduce the FREQUENCY SPAN/DIV to
50 kHz, then increase to 100 kHz and center the crt
beam on screen with the MANUAL SCAN control. Now
adjust FREQUENCY for a null (zero frequency) of the
display on the test oscilloscope.
Calibration—492/492P Service Vol. 1 (SN B030000 & up)
Adjustment Procedure
10. Adjust MANUAL SCAN to position the crt beam
four divisions from the center screen reference (four divi
sions represents 400 kHz).
11. Monitor and trigger the test oscilloscope on
TP1031 at the top of R1038 (Fig. 3-54B) and adjust the
Error Count Breakpoint potentiometer R1061, from its
mid-range position, clockwise until the display just starts
to break up.
12. Move the crt beam four divisions to the other side
of center with the MANUAL SCAN control and note that
the square wave response again starts to break up
400 kHz from center. As the beam crosses center, the
display on the test oscilloscope should go through a null.
If a null is not found, readjust center frequency. Adjust
R1061, if necessary, so break points are 400 kHz either
side of the null at center screen.
13. Reconnect P2035 between pins 1 and 2 and in
stall P3057. Disconnect the test oscilloscope trigger and
probe connections. Insure that P2035 and P3057 are in
stalled correctly; their absence will produce spurious re
sponses on the display.
14. Reduce FREQ SPAN/DIV to 50 kHz and ensure
phaselock occurs.
15. Replace the covers on the assembly and reinstall
the module in the 492/492P.
16. Perform the phaselock noise check as described
in the Performance Check part.
This concludes the Adjustment Procedure. Repeat the
appropriate Performance Check to verify specification.
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