"In the cases I have come across (two or three, I didn't document everything as well as I should) the accompanying symptom is severe aberration on the edges of the square wave from the calibrator."
Thanks to all for the helpful thread. In re Roger's comment above, the offending channel is characterized by the "severe aberration" he mentioned.
A fellow TEK junkie and I have several ill 7A26s and plan to correct them with a group session in the coming week.
Will report back!
--
William, k6whp
"A friend told me to cheer up, things could be worse.
So I cheered up and, sure enough, things got worse!"
k6whp