When I worked in television shops almost 30 years ago, I was sent out in
the field with a De-Gaussing coil and a tool roll for playing around with the
screens/guns/convergence, Etc. I'm not sure how good I did but the people
seemed happy

.... I'd flip ye ole set-up switch in the back or get the
bar generator out an play around for awhile ---- Darn those old flybacks
could bite though !!! ---- That darn De-Gaussing coil made me so much
easy money, and knowing to flip that set-up switch did too --- Then there
was the usual, horizontal output regulators/Vertical and retrace regulators...
You really couldn't go wrong with the SAM's and the fricken library in my town had so many ......... Those were the daze ...........