The Frequency Counter - HP 8753E Service Manual

The Main ADC
The main ADC is located on the A1~~~digita.l IF assembly and makes voltage
measurements in two ranges. See ~~~~~~~~~:,~, under "Analog In Menu".

The Frequency Counter

The frequency counter is located on the Al4 assembly and can count one of
three sources:
selected analog bus node
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range is 100 kHz to 16 MHz)
The counts are triggered by the phase lock cycle; one at each pretrme, acquire,
and track for each bandswitch. (The service mode, SOURCE PLL, must be ON
for the counter to be updated at each bandswitch). The counter works in swept
modes or in CW mode. It can be used in conjunction with ~S~~~~~.~~~~ for
troubleshooting phase lock and source problems.
To read the counter over HP-ES, use the command OUTPCNTR.
Notes
The display and marker units (U) correspond to volts
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Nodes 17 (1st IF) and 24 (2nd LO) are unreliable above 1 MHz.
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About 0.750 MHz is a typical counter reading with no AC signal present.
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Anything occurring during bandswitches is not visible.
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Past-moving waveforms may be sensitive to sweep time.
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The analog bus input impedance is about 50K ohms
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Waveforms up to approximately 200 Hz can be reproduced.
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