Center Frequency - HP 85662A Troubleshooting And Repair Manual

Spectrum analyzer if-display section

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A4A5 Step Gain, Troubleshooting

Operation of the Step Gains and AO.O to A15.9 Attenuator can be determined from the

display by several easy tests.

The Step Gains are checked in the following way. Connect a 10 dB step attenuator between

CAL OUTPUT and the input to the analyzer. Set this attenuator to 90 dB, press Instrument

Preset, and key in the following:

equal to the CAL OUTPUT frequency

f FREQUENCY SPAN)

[VIDEO B W )

( S W E E P )

[REFERENCE LEVEL)

sweep key and press the DATA STEP QQ key to display each step. Figure 5

should be displayed. If one or more of the steps is missing, refer to Note 8 for the Step Gain

truth table to determine which stage is faulty. 0 V in the table indicates that a control line is

R E F - 9 9 . 9 dBm

CENTER 2 0 . 0 0 0 0 0 0 MHz

RES BW 1 kHz

NOTE: C e n t e r

F r e q u e n c y r e a d o u t w i l l be 1 0 0 . 0 0 0 000 MHz for an HP8566B

Figure 5. 10 dB Step Gain Test

If a component has been replaced, a simple calibration/diagnostic program exists. The

calibration routine is started by connecting a cable from CAL OUTPUT to the input of the

analyzer and then pressing

(SHIFT") FRIQUENCY SPAN)

When this program has finished, press

TRIGGER w ichwill list the calibration data. (Refer to Figure 6). Lines 19

Troubleshooting