Re: Tektronix 7854 Digitization Issue

 

It acquires waveforms, but it's as though it's acquiring two different
waves, one at the correct frequency, and one approximately 1/5 the period.
I posted a video to YouTube showing an acquisition, you can clearly see
another superimposed portion of the wave across the entire sweep.
The "low frequency" that you see is actually the retrace (return of beam to left of screen). Have a look where it "ends" at the right side of the screen: Always where the real trace stops, so it's actually the starting point for the retrace. It should normally be invisible but blanking isn't set correctly for the digitisation.
It's likely that adjusting the "grid bias/blanking" for the digitisation part will solve your problem so check and if necessary adjust Z-axis levels. The Z-axis circuits are on the board mounted at the back, where the GPIB and battery backup connections are. It's not a dangerous adjustment in the sense that you may/will lose calibration.

Also, the rendered text gets wonky during an acquisition.
That is perfectly normal during acquisition.

Raymond

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