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Troubleshooting sampling scopes: Difference between revisions
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The second step is to get the timing (horizontal) unit working. The best | The second step is to get the timing (horizontal) unit working. The best | ||
technique here is to apply a pulse train waveform to the external trigger | technique here is to apply a pulse train (100mV, 1MHz, for example) waveform | ||
input of the timing unit while observing its | to the external trigger input of the timing unit while | ||
observing its outputs on a second oscilloscope. | |||
Some timing plug-ins such as the 3T77 provide a trigger pulse output on the | |||
front panel. Other plug-ins such as the 5T1A and 5T3 do not provide this | |||
signal on the front panel, so for those you have to probe the signal inside | |||
the plug-in. The timing plug-in is supposed to produce strobe pulses that | |||
are sent to the vertical sampling plug-in. If the timing plug-in isn't producing | |||
strobe pulses, typically you won't see anything on the screen. If it is producing | |||
strobe pulses, but they are not correct, you will get garbage on the screen. | |||
The two most common problems are that the timing plug-in either doesn't produce | |||
and strobe pulses, or the strobe pulses are not synchronous with the trigger | |||
signal (free-running). There should be some range of settings of the trigger | |||
sensitivity control where the plug-in produces strobe pulses when the trigger | |||
signal is applied and does not produce strobe pulses when the trigger signal | |||
is removed. | |||