Section 5 Maintenance
5-24
5-55. A5 CPU Adjustment.
5-56. The only adjustment on the CPU Board is the
Timebase Frequency Adjustment which is adjusted to
provide the specific frequency accuracy for the system
time standard.
5-57. A5Y1 Timebase Frequency Adjustment. Per-
form the procedure as follows:
a. Disconnect power from the instrument.
b. Remove the IEEE-488 interface cable on the CPU
Board.
c. Connect the House Standard frequency reference
to the rear panel X CLK input.
d. Apply power to the instrument.
e. Enter special function 35 to enable the frequency
counter check mode.
f. Observe the SOURCE display and adjust A5Y1
until the display indicates 10000.00 kHz ± 1 count.
h. Disconnect power from the instrument.
5-58. A3 Notch Board Adjustments. The Notch Board
adjustments consist of A3R57 Notch Balance and A3R58
Notch Tune. These adjustments compensate for offsets
in the notch filter which could reduce the effective depth of
the notch.
5-59. A3R57 Balance and A3R58 Tune Adjustments.
Perform the adjustments as follows:
a. Depress the LCL/INIT key to initialize the instru-
ment.
b. Connect the Source HI and LOW outputs to the
Analyzer HI and LOW inputs using the balanced cable
and adapters.
c. Connect the Wave Analyzer input to the MON-
ITOR output on the rear panel of the Audio Analyzer.
d. Set the Wave Analyzer control as follows:
SCALE.............................................. 90 dB
FREQUENCY................................... 1 kHz
AMPLITUDE REF LEVEL................. NORMAL
INPUT SENSITIVITY........................ 10 dB
RESOLUTION BANDWIDTH ........... 10 Hz
AFC .................................................. OFF
SWEEP MODE................................. OFF
e. Set the Source level to 3.000 volts and depress the
Analyzer DIST key.
f. Observe the Wave Analyzer and alternately adjust
A3R46 and A3R49 for a minimum indication. The null
measurement should be in excess of 40 dB.
5-60. A0 Input Board Adjustments.
5-61. The Input Board adjustments consist of four com-
mon mode rejection adjustments: A0R29 and A0C35 3 V
Range CMRR, A0R12 30 V Range CMRR and A0R7300
V Range CMRR, and four flatness adjustments: A0C5 HI
Input 30 V Range Flatness, A0C32 HI Input 300 V Range
Flatness, A0C10 LOW Input 30 V Flatness, and A0C33
LOW Input 300 V Flatness.
5-62. A0R29, A0R12, A0R7 and A0C35 CMRR Ad-
justments.
Perform the adjustments as follows:
a. Depress the LCL/INIT key to initialize the instru-
ment.
b. Enable the Analyzer input float mode and connect
the Source HI output to the Analyzer HI and LOW inputs
using BNC cables and a TEE adapter.
c. Connect the Wave Analyzer input to the MON-
ITOR output on the rear panel of the Audio Analyzer.
d. Set the Wave Analyzer controls as follows:
SCALE.............................................. 90 dB
FREQUENCY................................... 1 kHz
AMPLITUDE REF LEVEL................. NORMAL
INPUT SENSITIVITY........................ 0 dB
RESOLUTION BANDWIDTH ........... 10 Hz
AFC .................................................. OFF
SWEEP MODE................................. OFF
e. Set the Source level to 3.000 volts and enter
special function 28.
f. Observe the Wave Analyzer and alternately adjust
A0R29 and A0C35 for a minimum indication. The null
measurement should be in excess of 75 dB.
g. Enter special function 27.
h. Observe the Wave Analyzer and adjust A0R12 for
a minimum indication. The null measurements should be
in excess of 75 dB. If a 75 dB null cannot be achieved,
alternately adjust A0C5 or A0C10 flatness adjustments
and A0R12 for a null in excess of 75 dB.
i. Enter special function 26.
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