HP 83522A Service Notes page 186

A4 ALC TROUBLESHOOTING (CHANGE 8) (Cont'd)
RPG / POWER DISPLAY FAILURE
Check that the POWER display changes when either the RPG is rotated or data is entered via the
Model 8350A/B keyboard. This verifies that the digital information is reaching the mainframe,
is properly processed, and is then displayed.
If the display is flashing rapidly or showing random patterns, refer to Al/A2 Front,Panel or
A3 Digital Interface Troubleshooting. If the RPG causes a change in the measured RF
power level, but the POWER display remains the same, refer to Al/A2 Troubleshooting. If
the RPG produces no response whatsoever, or if the front panel display is blank, refer to
A1/A2 Troubleshooting, and trace the problem back to the Model 8350A/B mainframe.
UNLEVELED (LED)
If the UNLEVELED light turns on during the sweep, enter a sweep time of 2.4 seconds (i.e. one
second per GHz). Observe the SWP light on the Model 8350A/B Sweep Oscillator, and
determine at which times during the sweep the UNLEVELED light turns on.
If the UNLEVELED light remains lit during retrace, suspect problems in the front panel
annunciator drivers. Refer to AlIA2 Troubleshooting.
If the UNLEVELED light blinks briefly at the beginning of the sweep, the plug-in may be
sweeping through 0 Hz and causing an ALC drop-out. Check this by slowly increasing the
start frequency. If the UNLEVELED light stops blinking, enter a CW frequency of 50 MHz
and adjust the Model 83522A front panel FREQ CAL screw until the MKR light stays on.
Press [INSTR PRESETJ and observe the UNLEVELED light.
A
frequency counter may be
used to check frequency accuracy at 10 MHz or 50 MHz. If necessary, refer to Section
V,
Adjustments, in this manual, and perform the Frequency Accuracy calibration procedure.
If the UNLEVELED light flashes briefly during the sweep, but does not imply the above
failure modes, check power flatness. See below.
FLATNESS
/
OSCILLATIONS (Power Dropouts)
Monitor the RF output with the HP 8756A as shown in Figure 8-26.
If the power level is constant across the sweep within approximately 5 dB, then the plug-in
may only require ALC flatness adjustments. Refer to Section V, Adjustments, in this
manual, for the Internal Leveled Flatness adjustment procedure.
If the measured power level lies between
+
13 and
-
2 dBm, but cannot be controlled via
the front panel, refer to the Digital Control section under Troubleshooting Diagnostics.
If the trace appears chopped or broken, the loop may be oscillating. Refer to Section V,
Adjustments, in this manual, and perform the ALC Gain adjustment procedure.
CHANGE 8