Tuesday, September 28, 2021

Tek 7A26 Problems

 Not to pile on re 7A26es, but I have one that is misbehaving and wanted some help finding the starting point to the debugging process. The problems are as follows:

(1) The top channel "IDENTIFY" button does not work. I've been through the manual and schematics -- admittedly, not thoroughly -- and am unable to find the "secret workings" of that device. I pick up the  push button at the CH 1 AMP schematic where is says "probe identify from R13" but cannot seem to locate R13. et seq.

Also, if anyone knows the theory of how this works, I would be much obliged.

(2) The top channel (except for the "IDENTIFY" problem) works fine. The bottom channel does not. Plain and simple the display is faulty. The two channels are shown below for comparison and taken from the 4V 7044A frame square wave standard. Both are measured with a stock Tek P6131 probe. Any thoughts on this would be welcome.

Thanks in advance.


Channel 1 (Top) Good

Channel 2 (Bottom) Bad