HP 8568B manual LC Dip Adjustments

8.21.4 MHz Bandwidth Filter Adjustments

45.Adjust A4ABR40 XTAL to align markers on display. MARKER A level should indicate 1.00 X. See Figure 3-44 for location of adjustment.

LC Dip Adjustments

46.Refer to the Resolution Bandwidth Switching Uncertainty Performance Test, and check all bandwidth amplitudes. If amplitude of 300 kHz bandwidth is low but amplitude of 100 kHz and 1 MHz bandwidths are within tolerance, LC DIP adjustments must be performed. If all bandwidth amplitudes are within tolerance, do not perform the following adjustments.

47 . Set LINE switch to STANDBY.

48.Disconnect cable 97 (white/violet) from A4ABJl and connect to A4A6 J 1.

49.Remove A4A4 Bandwidth Filter and install on extenders.

50.Set LINE switch to ON. Press ~NSTR PRESET).

51.Key in [CENTER FREQUENCY] 20 MHz, [RES] 100 kHz,

~FREQUENCY SPAN] 1 MHz, [ATTEN) 0 dB, and LOG (ENTER dB/DIv] 2

dB.

52.Short A4A4TP3 to ground.

53.Adjust. A4A4C41 LC DIP for minimum amplitude of signal peak. See Figure 3-41 for location of adjustment. Key in CPEAK SEARCH) MARKER Ln], and adjust LC DIP again to offset the signal peak approximately -17 kHz (to the left). This is done to compensate for the effect of placing the board on extenders. If unable to achieve a “dip” in signal amplitude, increase or decrease value of A4A4R16. Refer to Table 3-3 for range of values.

54.Remove short, from A4A4TP3 and short A4A4TP8 to ground.

55.Adjust A4A4C43 LC DIP for minimum amplitude of signal peak. See Figure 3-41 for location of adjustment. Key in [PEAK SEARCH) MARKER In], and adjust C43 LC DIP again to offset the signal peak approximately -17 kHz (to the left). If unable to achieve a “dip” in signal amplitude, increase or decrease value of A4A4R60. Refer to lhble 3-3 for range of values.

56.Set LINE switch to STANDBY.

57.Reinstall A4A4 Bandwidth Filter without extenders. Short A4A4TP3 and A4A4TP8 to ground. Remove A4A8 Attenuator-Bandwidth Filter and install on extenders. Reconnect cable 97 to A4ABJl and reconnect cable 89 to A4A6Jl.

58.Set, LINE switch to ON. Press QNSTR PRESET).

59.Key in [CENTER FREQUENCY) 20 MHz, CRES] 100 kHz,

(FREQUENCY SPAN) 1 MHz, [ATTEN] 0 dB, and LOG (ENTER dB/DIV] 2 dB.

60.Short A4ABTP6 to ground.

61.Adjust A4ABC66 LC DIP for minimum amplitude of signal peak. See Figure 3-43 for location of adjustment. Key in CPEAK SEARCH) MARKER @, and adjust LC DIP again to offset the signal peak

3-82 Adjustments