For the following designations I'm using PV "XR power amp" schematic as
only preA seems available for the XR684

Two base connected o/p 2SA1302 ,only, of the R ch are heating up for a
second,driven from Q213(E) .
At this stage don't know if an internal problem to one of those pair ,
or as quite accurate "timing" of excursion, I'll put a monitor on
Q213{B} as its probably a further back excursion in the splitting area ,
involving a cap perhaps to give the timing.
Enough for today