Folks
A few months ago I noticed some strange behaviour on a couple of the digital channel on my MSO1074Z-S. Although a signal was showing, the high time was very short, much shorter than expected, of the order of about 15ns or so when the width was really about 40ns in a specific test I made up to reproduce the problem. Other digital (and analogue) channels on the same signal were fine.
The problem was intermittent but more recently it became almost permanent on one of the channels. Because it's my field scope, it doesn't get much use in the lab, so I never got around to fixing it until now.
To cut a long story short, it turned out to be a very mundane fix: clean out the cable and scope connectors with a quick spray of IPA and an air duster. I assume one of the differential connections from the cable connector wasn't making contact.
Frustrating, because I went as far as having the probe apart, and was probing the probe... which is why one scope is never enough!
Hopefully this'll help others if they encounter a similar fault.