TB 9-6625-1982-24
(4) INTERNAL INPUT COUPLING switch to DC (up) (Two-position slide switch
AC or DC coupled) (fig. 4). Position all other internal switches in the down position (remove
side cover for access to internal switches).
CAUTION
To avoid damage to the plug-in circuitry, power must be OFF
on the mainframe power module before connecting the TI.
b. With power OFF, connect TI to mainframe power module using extender.
c. Pull mainframe power module ON-OFF PWR switch to ON and allow at least 30
minutes (60 minutes if stored in high humidity environment) for equipment to warm-up
and stabilize.
d. Remove left or right side covers of TI as necessary to make connections or
adjustments. Replace cover(s) after completing adjustments.
25. Time Base
NOTE
Adjustment of the Time Base Oscillator is no longer performed
unless an out of tolerance value is determined while
performing the Time Base Performance Check.
a. Performance Check
(1) Connect TI 1 MHz Test Point near C172 (fig. 4) using 10 X probe to frequency
difference meter SIG INPUT.
(2) Connect time/frequency workstation 1 MHz OUTPUT to frequency difference
meter REF INPUT.
(3) Verify that the difference indication on the frequency difference meter is within
130 PPM.
(4) If within tolerance disconnect connections made in a (1) and a (2) above and
proceed to next paragraph. If out of tolerance perform b below.
b.
Adjustments
(1) Adjust time base oscillator 1 MHz Clock C172 (fig. 4) to obtain minimum
(2) Allow oscillator time to settle (at least 1 hour) after making adjustment and
verify it has not drifted. If needed repeat (3) above.
(3) Disconnect connections made in a (1) and a (2) above.
(4) No further time base adjustments can be made.
