On Fri, 22 Jan 2016 15:45:32 -0800, John Heath wrote:

Interesting problem. Many great suggestions have been put on the table
from different members so there is not much to add. The resister that is
running too hot is telling us something. Why is that resister not a
happy camper? What is it connected to. There is a hiss or possibly
plasma arcing and a resister that is not happy. looking at a diagram to
see what the unhappy resistor does in the power supply could provide a
clue.

Yes, a schematic would be extremely useful but I don't have the precise
one; just a similar model of scope with a similar ps section. Some parts
are correct and in the right place, others aren't. You have to work with
what you've got. Hopefully tomorrow I'll discover a few more clues...