I fixed the 7B53As. The board mounting screws on one of the
inner boards were loose. Tightned the screws and both
the 7B53As now behave themselves.
That didn't help the 7B92. I tweeked the HF compensation
for minimum effect. It's still not right, 20nS ramp looks like
a stairway, but at least the
sweep doesn't run backwards any more. This is gonna be impossible
to find by probing around with a scope. The effect is smaller
than the ambient ground noise. Extender just makes it much worse.
mike
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--- In TekScopes@..., "Craig Sawyers" <c.sawyers@t...> wrote:
I have two 7B53As and one 7B92 sweep plugins.
In a 7704A, they all have similar problems.
There's no pretrigger leadtime, can't see the leading
edge of the waveform.
The trace unblanks about 4 nS after the edge. The sweep isn't even
monotonic in that first 150nS. The sweep actually reverses
in 16nS intervals creating a bright spot and severe distortion
if you move an edge through the region.
I've just checked out my 7704A using a 7B92A - and it works just fine. None
of the effects that you describe.
Craig
