Help with a Tek 7A26

k6whp
 

Gentlemen (and ladies),

I have a sick 7A26 which I would seek advice on. The symptoms are as succinctly as follows:

(1) The vertical measurements are inaccurate; they are approximately 2/3rds of the correct value.
(2) The problem is common to both channels.
(3) The calibration of the unit does not provide sufficient range to correct the problem.

I have gone through the manual and have run the troubleshooting flow chart cursorily (he shamefacedly admits) and have scoured the schematics but would request help. I am NOT looking for a solution to be suggested (although, if something occurs..) but would appreciate a pointer or two on where to begin. I am going to borrow a friend's good 7A26 and "ohm the rails" as well as take comparative measurements on both. (I have a 7704A and can put the 7A26 in the left most slot to do the probing.) I would be grateful of some recommendations as to where to start snooping.

I am more interested in learning than ONLY fixing.

Thank you for your patience and suggestions.
--
William, k6whp
"A friend told me to cheer up, things could be worse.
So I cheered up and, sure enough, things got worse!"

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