Agilent Technologies 856290216 service manual Cal fist Troubleshooting Nude

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; A5 IF ASSEMBLY

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CAL OSC

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W27

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( O R A N G E )SK171

Figure 9-2. IF Section Troubleshooting with the TAM

Both the digital control and DACs are multiplexed onto test point “channels” through resistive networks. One DAC from each of the quad-DAC packages feeds into a network. The TAM varies each DAC individually to isolate which ones failed. Similarly, 10 digitally-controlled lines feed into a network and are monitored by the TAM. The channels used to monitor the DACs are listed below:

Channel A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A5J9 pin 1 (MSl) Channel B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A5J9 pin 3 (MS3) Channel C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A5J9 pin 4 (MS4)

Channel D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A5J9 pin 2 (MS2)

1.On the HP 85623 spectrum analyzer, press (PRESET), MOIIULE , and Diagnose. Select

Cal fist Troubleshooting Nude.

2.On the HP 85623 spectrum analyzer, disconnect W27 (coax 3) from A5J5 and monitor the output of A5J5 with a second spectrum analyzer.

IF Section 9-7