Most failures I've seen in Tek scopes were in the high voltage section. They like to use quadruplers, and tend to lose the occasional diode. They are high voltage types, and do not check with just a few volts applied. Not too big a deal to replace, though.
We had a 475 that turned into a turkey, though, because the switches in the second vertival channel did not make reliable contact. They were little gold leaves, and hinged down to make contact. They never were reliable, even after sending the scope in for cal/repair.
I've got a Tek 2221A now. It's only 100 MHz, so it's pretty weenie for logic work. I do mostly analog work, so it's great. Dual analog channels and digital storage. Couldn't be better.