L Hb And L Lb Lines - HP 8753D Option 011 Service Manual

These complementary signals toggle when the instrument switches from

L HB and L LB Lines.

low band to high band as illustrated by Figure 7-16.
Figure COMPSIG7 here.
Figure 7-16. Complementary L HB and L LB Signals (Preset)
If all of the digital signals appeared good, the 12 assembly is faulty.
A 3/A 4 Fractional-N Check
Use the analog bus or an oscilloscope to check the 14 VCO's ability to sweep from 30 MHz
to 60 MHz. The faster analog bus method should suce unless problems are detected.
Fractional-N Check with Analog Bus
1. Press
RESET SYSTEM
5
ANALOG IN Aux Input FRAC N
2. Then press
MENU CW FREQ
5
3. Set the instrument as indicated in Table 7-5 and see whether the VCO generates the
frequencies listed.
Instrument etting
1 MHz
60.999999 MHz
4. Check the counter reading at the frequencies indicated.
If the readings are within the limits speci ed, the probability is greater than 90% that
the fractional-N assemblies are functional. Either skip ahead to the \ 7 Pulse Generator
Check," or perform the more conclusive \ 14 VCO Range Check with Oscilloscope"
described below.
7-22 Source Troubleshooting
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ERVICE MENU ANALOG BU ON
5
to switch on the analog bus and the fractional-N counter.
to set the analyzer to CW mode.
5
Table 7-5. VCO Range Check Frequencies
PARAMETER
MEAS
5
Counter Reading
0 0.0 0 MHz
60 0.060 MHz
3/21/106 15:13
RAFT