
Service Related Menus 8712ET/ES and 8714ET/ES
Analog Bus Menu RF Network Analyzers
5-16 Service Guide
Analog Bus Menu
The analyzer has an analog bus that can be used to troubleshoot hardware problems on
some of the boards in the analyzer. This is done by sampling analog bus nodes, which
provide measurements at selected points on the boards. Nominal values for each node are
provided in Table 5-4.
: Allows you to select an analog bus node to be measured. The currently
selected node description and number are displayed. A node may be selected by using the
keypad to enter the number, or by using the front-panel knob or the keys to scroll through
the list.
: Triggers a data measurement of the selected analog bus node.
Table 5-4 Analog Bus Nodes
Number Name Description
A4 Source Assembly Nodes
1 +47 V (for 8712ET/ES)
+22 V (for 8714ET/ES)
Source assembly power supply. Nominal value:
+44 V to +50 V (8712ET/ES)
+20 V to +24 V (8714ET/ES)
2 VCO RF 1 Tune VCO tuning voltage for the RF1 phase lock loop on
the source board (RF1_TUNE on the schematic).
Typical values are 7 to 11 volts. A value higher than
about 11.5 V may indicate a saturated op amp or
bad VCO.
3 LO Integrator Output of integrator in the source LO loop (LO_INT
on the schematic). Voltage decreases as source
frequency increases. For the 8712ET/ES, the voltage
decreases about 9 volts over the frequency range.
For the 8714ET/ES, the voltage decreases about 7
volts over a.3 to 1910 MHz range; voltage shifts at
about 1910 MHz.
4 VCO Offset Tune VCO tuning voltage for the RF2 phase lock loop on
the source board (OFFSET_TUNE on the
schematic). Value varies with the source frequency
setting. Normal values are 6 to 10 volts. A value
higher than about 11.5 V may indicate a saturated
op amp.
5 Output Amp Temp Shows the temperature at the output amplifier on
the source board (OUTPUT_AMP_TEMP on the
schematic). Normal values are 30 to 45 degrees
Celsius. Not available on the 8714ET/ES.
6 ALC Log Amp ALC log amp output on the source board (ALC_LOG
on the schematic). Value depends on the source
power level. Normal values are −1.75 to −0.5 volts.
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