HP 8924C Assembly page 586

Chapter 14, Diagnostics Descriptions
Description of RF Diagnostics (RFDIAGS3)
Table 125
Measurement
Output Detec- The detector is checked with the carrier level DAC at
tor, Detector a high level (4000). Then the detector caps are
Caps switched in separately and together. The detector's
voltage should not change as the caps are switched in
and out. If the jumper coax between the output of the
signal generator's Synthesizer and the input to the
output section fails, the detector capacitors test will
fail. This is a rather common failure.
Output Detec- The carrier-level DAC is set to a low level (0) so there
tor, Low Level should be no RF signal reaching the RF detector.
Output The ALC loop is closed and the signal generator Syn-
Frequency thesizer's frequency is set to all values from 1 to 1001
Range, Loop MHz in 100 MHz steps. The detector voltage is mea-
Closed sured at each frequency.
Bandwidth The bandwidth control bits are set to all combinations.
Control This should not change the output level.
Tracking Filter The ALC loop is opened and the tracking filters are
Rejection checked by setting the RF frequency to the center of
the 2 bands (375 and 750 MHz) that use these filters.
Then the filter DAC is changed to tune the filters
below the RF frequency. The RF level as measured by
the output detector should be close to zero.
586
A26 Output Tests (Continued)
Explanation and Suggestions Measurement Point
DVM:OUT_OUTPUT_ LEVEL
DVM:OUT_OUTPUT_ LEVEL
DVM:OUT_OUTPUT_ LEVEL
DVM:OUT_OUTPUT_ LEVEL
DVM:OUT_OUTPUT_ LEVEL
N:\mkt\MANUALS\HP8924C\ALR\diagnos.fb