HP 8568B Figure 3-55.Location of A27A2 Adjustment, 12.Time Base Adjustment (SN 2848A to 3217A05567)

12.Time Base Adjustment (SN 2848A to 3217A05567)

15.On the Frequency Counter, select a 1 second gate time by

pressing, t-1 1 @Y%YiK]. The Frequency Counter should now display the difference between the frequency of the INPUT A signal and 10.0 MHz with a resolution of 0.01 Hz (10 mHz).

Note Do not use a metal adjustment tool to tune an oven-controlled crystal oscillator (OCXO). The metal will conduct heat away from the oscillator circuit, shifting the operating conditions.

16.Use a nonconductive adjustment tool to adjust the 18-turn FREQ ADJ capacitor on the A27A2 10 MHz Quartz Crystal Oscillator for a Frequency Counter indication of 0.00 Hz. See Figure 3-55 for the location of the A27A2 10 MHz Quartz Crystal Oscillator.

R F S e c t i o n ( b o t t o m view)

Figure 3-55. Location of A27A2 Adjustment

17.On the Frequency Counter, select a 10 second gate time by pressing, [GATETIME) 10 C-1. The Frequency Counter should now display the difference between the frequency of the INPUT A signal and 10.0 MHz with a resolution of 0.001 Hz (1 mHz).

18.Wait at least 2 gate periods for the Frequency Counter to settle, and then adjust the FREQ ADJ capacitor on the A27A2 10 MHz Quartz Crystal Oscillator for a stable Frequency Counter indication of (0.000 + Frequency Correction Factor) fO.O1O Hz.

19.Replace the RF Section bottom cover and reconnect the short jumper cable between the FREQ REFERENCE INT and EXT connectors.

3-102 Adjustments