2. Service
Assembly/Module Diagnostic Trees (Diagnostic Section 3)
118
3.8.3.2 A15 +4.5V Test
1 Measure the dc voltage on the +4.5V terminal on A15 (accessible on the
underside of the instrument when the bottom cover is removed).
2 Verify voltage between +4.4V and +4.6V.
QUESTION: Is voltage correct?
If Yes: Go to, 3.8.3.2.1.
If No: Go to, 3.8.3.3.
3.8.3.2.1 A15 320 MHz Input Test
1 Disconnect cable from A15J4. Adjust input attenuation on spectrum analyzer
for +30 dBm. maximum signal.
2 Connect free end of cable to spectrum analyzer.
3 Verify the presence of a signal with a frequency of 320 MHz and amplitude of
at least +18 dBm.
4 Reconnect cable to A15J4.
QUESTION: Does the analyzer show a signal with frequency of
320 MHz and amplitude of at least +18 dBm?
If Yes: Remove power, replace A15, and retest.
If No: Go to, 3.4.1.0 (A9 diagnostic tree).
3.8.3.3 A18J3 DC-Voltage Test
1 Disconnect cable from A18J3.
2 Use a DMM to carefully check the dc voltage of the A18J3 center pin.
3 Verify that the voltage is between +4.4 and +4.6V.
QUESTION: Is the voltage between +4.4 and +4.6V?
If Yes: Go to, 3.8.3.4.
If No: Remove power, replace A18, and retest.
3.8.3.4 A18J3 to A15/+4.5V Cable Test
1 Remove instrument power.
2 Check continuity of A18J3 to A15/+4.5V cable with a DMM.
3 Check for short or open condition.
QUESTION: Is it shorted or open?
If Yes: Replace cable.
If No: Replace A15.
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