"Phil Allison" wrote in
:


"Geoff"

Left side of trace has a ripple, about 1/2 division vert
amplitude and about 25% of horizontal is affected.
Both channels the same
When vert offset is manually swept, the pattern of ripple
changes, still both channels the same
Timebase does not change shape or size of ripple
ripple is 1/2 or 1 cycle but is like someone has put a
magnet on the side of the tube.


** Could the case be magnetised in one area ?




... Phil



I took the case off and no difference, your implied suggestion
that a change in magnetic field caused this matches what I
observe, ie no electronic settings change the waveform, it looks
like when someone shoves a magnet near a crt. I have not removed
the tube screen but I have shaken it and nothing like a magnet
bouncing around can be heard, I may just give up now, it is not
a paying job just an old CRO we use occasionally for R&D work,
we have newer better ones around including tek analog CRO's.