R760 and the associated components (Q708, Z702) are a quick and dirty voltage regulator that provides the initial voltage needed to start up the horizontal circuit. The circuit supplies roughly 8-9 volts to get the horizontal circuit running, once running, 15v from a secondary of the flyback takes over, supplying the needed current for normal circuit operation.
This startup circuit cannot supply any significant amount of current for any extended periods of time, if the horizontal circuit doesn't start up for any reason, the startup circuit, which r760 is part of, will continue supplying current and start burning up.
At this point I would go over the entire horizontal circuit. It's hard to be specific, since anything that stops the horizontal circuit from running will give you these symptoms. After checking for cold or bridged solder joints, I would look for improperly installed components (backwards cap, etc..) then I would suggest checking all the transistors and diodes in the horizontal circuit for shorts, then open resistors and so forth.
It's a bastard of a chassis to work on, so I do wish you the best of luck with it.
D