TB 9-6625-1982-24
(4) CHANNEL B - AUTO TRIG LEVEL knob to mid point.
(5) CHANNEL A and CHANNEL B COUPL buttons AC (in), all other buttons
(SLOPE, ATTEN, COUPL) in (out) position.
d. Pull mainframe power module ON-OFF PWR switch to ON and allow at least 30
minutes (60 minutes if in high humidity) for equipment to warm-up and stabilize.
41. 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 time/frequency workstation 1 MHz OUTPUT using cable and 50
termination (if needed) to TI CHANNEL A EXT INPUT.
(2) Set the TI CHANNEL A LEVEL control for a stable readout.
(3) Verify that the TI readout is within 6 PPM (999994.0 to 1000006.0).
(4) If within tolerance disconnect connection made in a (1) and proceed to next
paragraph. If out of tolerance perform b below.
b. Adjustments
(1) Adjust C1602 Osc Adj (fig. 8) until the TI readout indicates between 999.99990
KHz and 1.0000001 MHz. (OPT01) Adjust Y1531 (through an access hole in the back of
oven timebase located on back side of Analog board) to indicate between 999.99998 kHz and
0.00000002 MHz (display flashing indicating OVERRANGE).
NOTE
Depending on AVERAGES setting it could take 1-10 seconds
for the display to update after adjusting the oscillator.
(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 step a (1) above.
(4) No further adjustments can be made.
