Re: Advice on fixing 2465B slow horiz sweep


Siggi
 

On Thu, Jul 22, 2021 at 6:02 PM Grayson Evans <wa4gvm@gmail.com> wrote:

My 2465B has been sitting on the shelf for a few months. I notice when I
fired it up today that the horizontal sweep is slow, by that I mean that
the
calibrator square wave does not line up with the screen scale lines. It
sweep starts out on the left correct but by the time it reaches the right
side, it is off about 1/2 cm.
I checked the calibrator output on another scope and it is correct. The
Delta T measurement shows that the calibrator timing is correct, but it
just doesn't line up with the screen scale. Same for B sweep.
If you're seeing this only for the sweep speed, but consistently for *all
sweep speeds* *and for the cursors*, then possibly your horizontal gain has
drifted.
What's more likely happening is that your scope is suffering from the 2465B
capacitor plaque, where the electrolytics on the A5 board leak and wreck
the DACs reference (among other things). This would affect the sweep speed,
but also a whole lot of other functionality on the scope. If you haven't
already changed the electrolytics on the A5 board, it'd be my bet that
that's your problem.

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