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 11