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Old 26th Jun 2013, 4:17 pm   #14
dave cox
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Join Date: Jan 2009
Location: Bristol, UK.
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Default Re: Tektronix 465B Scope - Some problems.

The quick way to check for ripple in the trace is to set the trigger source to line and feed in a signal close to 50Hz. If you just have 'ripple' you should see a clean trace that just wobbles up and down a bit at the beat frequency.

However, to me, it looks like you have a bit of oscillation or breakthrough. Try working your way through the faster time-base settings (and variable) to see if you can get a beat frequency to identify the interference frequency (if there is one).

Your 'single spot' test, to me, would seem to indicate that its coming into the XY plate drivers, this is typically fed from +/- 50-150V rails. In my experience, this area is mighty sensitive to any interference. Is it me, or does the second 'spot' picture look a bit diagonal ? If so then it could indicate some interference common to X and Y.

dc
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