If indeed you have a power supply problem, then the BEST plan of attack is to work on the power supply only "outside of it's environment. That is with loads attached at probably 80% of the rating, A lot of times, only one or two supplies need that load. Without it, the power supply can be damaged.
Switching supplies are a "tough beasts" to repair because usually it's all or nothing. Variacs won't usually help.
There is a large number of Tek products that are plagued with bad caps. They leak and destroy the traces. What this means is you can be led astray thinking your looking for a bad component when, in fact it's a "bad wire(PCB trace)".
Make sure you join the tekscopes group at groups.yahoo.com.
I can do both: mechanical and electrical. I had full machine shop privledges where I used to work. Well, almost full. The "director" of our department limited th access to the MIG welder. I did well before the restriction was in place. It was a "new toy" at that point and I got to take it for a test drive. I did well, once the machine was "set-up". I was the best at silver soldering.+
That's how I learned the milling machine. The setup had to be "approved" by the resident machinist before I could proceed. Later, I was one of the people who could provided that service after the machinist left.