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Triggered Sweep
The triggered sweep modes are very similar to free run operation except that instead of the
Al5 Controller outputting a set HSWP command to the
A3Al
Trigger assembly, it outputs a
trigger enable command. The output of the trigger select circuit (line, external, or video) then
clocks the HSWP line high.
Single Sweep
The single sweep mode is useful in troubleshooting the sweep system because it does not rely
on feedback from Digital Storage before resetting the sweep generator. Whenever the SWEEP
(ZiK$
key is pressed, the Al5 Controller resets the sweep generator and then sets HSWP
high through the
A3Al
Trigger assembly. Digital Storage then stops the sweep when it has
reached the end and the ramp resets to 0 V.
Fast Sweep
Fast sweep is enabled only for 0 Hz frequency spans and sweep times less than 20 ms. HSWP
is forced low, and the Al6 Sweep Generator is not used. See
A3Al
Trigger for a description of
the fast sweep operation.
Service Requests
Any of the Service Requests on the Al2 Front-Panel Interface will force LSRQ low which
forces HSWP low. For example, when a front-panel key is depressed, a keyboard Service
Request is generated. LSRQ goes low, LSTP goes high, and HSWP goes low stopping the
sweep. Depending on which key was pressed, the Al5 Controller will either continue the
sweep or reset it and start a new sweep. Note that the analyzer cannot sweep if any Service
Requests are present.
Sweep System Troubleshooting
The following procedure is an aid to rapidly isolate sweep system malfunctions. When the
malfunction has been traced to a single assembly, check the Service Sheets for that assembly
for a more thorough troubleshooting procedure.
Isolate the Scan Sweep
Disconnect the ramp from
A3A8Jl
and jumper
A3A8TPl
to
A3A8TP2.
This forces the ramp
comparator output high. The Digital Storage Processor Section should continue to process
data and increment the sweep address. The HSWP light should be flashing and HSWP should
have an approximately 16 ms pulse width. (Note that the instrument preset state may appear
to be functioning properly but will become distorted as the sweep time is slowed down.)
If this works, the Digital Storage Processor Section and Al5 Controller, Al2 Front-Panel
Interface, and
A3Al
Trigger assemblies are operating properly. Suspect the ramp generator
or Al6 Scan Generator or ramp converter on the A3A8 Analog-Digital Converter. To further
isolate the scan generator, reconnect the sweep ramp to
A3A8Jl
and remove the jumper. Set
the sweep time to 1 second and press the SWEEP
(ZiKZiY]
key. The ramp waveform will start
at greater than 10 V, go to 0 V when the SWEEP
[SINGLE]
key is pressed, and ramp back
Overall Troubleshooting
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