Re: Tektronix 2465. Odd wave pattern superimposed on waveforms.


Siggi
 

On Mon, 11 Jun 2018 at 22:12 John Osborne via Groups.Io <JohnROsbor=
aol.com@groups.io> wrote:

The scope displays a good sine wave on all inputs. But superimposed on the
perfect sine wave is a rippling wave that travels from right to left in
quick succession. Perhaps 6 waves per second. It does not distort the sine
wave in any way but travels along the wave on both the top and bottom edge
of the trace. The wave is much lower in intensity than the sine wave
displayed but is very noticeable.
Hey John,

welcome to the group and congrats on the 2465 - sounds like you'll feel
right at home here :).
At low sweep speeds, the 2400 scopes borrow the beam during the sweep to
update the on-screen display (OSD). This causes a little bit of artifacting
in the waveform that could manifest as you describe.
If this is what you're seeing, you should be able to verify that the
artifacting goes away when you turn off the OSD, which you do by turning
the display intensity pot to the 12 o'clock position.

IIRC there's an adjustment for this somewhere, though I'd have to grouse
through the service manual to find it.

Siggi

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