Re: 7A26 edge distortion


John Gord
 

Raymond,
The 7A26 has a number of small ceramic trim caps of a design that has proved to be prone to going open circuit. You may have failures at the same point of both channels, unlikely as that seems. I would suspect C1432 and C2432 in particular, since they seem likely to affect the highest frequency signals. Try turning them: if they have gone open circuit turning them will have little to no effect. If those are not the problem, try others!
--John Gord

On Tue, Oct 20, 2020 at 07:20 PM, Raymond Domp Frank wrote:


Dear experts,
One of my 7A26's distorts a 1 ns falling edge (PG506, followed by 50 Ohm
attenuator) as shown in this photo:

https://groups.io/g/TekScopes/album?id=255438

Both channels show the same. I've looked for what I considered obvious
problems like the Display Switching area (7A26 SM dwg 4) but haven't found the
cause yet. Other 7A26's show the edge fine.
Any ideas?

Thanks,
Raymond

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