Delayed trigger jitter on 535A


cmjones01
 

Tek fans,

My much-loved 535A has been getting a lot of use over the last few
weeks. It lives in my home lab which is where I'm now working due to
the coronavirus situation. Generally it's been a delight to use but
there's one niggle I think I need to sort out.

When using 'A' delayed by 'B' horizontal display mode, the trace has
significant horizontal jitter. For example, yesterday I was viewing a
1kHz rectangular wave and using the delayed timebase to examine one
edge. With timebase A set to 0.5us/cm, the viewed edge jitters back
and forward about 1-2us. The fault isn't always there - trying the
same test with the calibrator output, it was steady for the first 10
minutes or so and then got jittery.

If I back off timebase 'A's stability control so that it's triggering
on the edge after the delay, the jitter disappears as expected, so
it's something to do with the delay.

Before I start digging in to find the fault, has anyone experienced
anything like this with a dual-timebase 500 series scope -
535/545/546/547/549? I guess they're all fairly similar apart from
perhaps the 547.

Thank you
Chris

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