I convinced myself that the low switch on surge was not for the main Tx
and should have checked there first. Went down the farting about route.
Removing a cable tie to move a filter toroid and rats nest of thick cables
I could see one end of the elusive fuse. The primary side of the Tx is
not probable except at that point and 2.1R to mains neutral, standby Tx
4.4K. Pushing a thin brazing rod through a hole in a rear pcb it was
possible to make contact with the other end of that fuse and ok.
Powering up and 5.9V over the 6V power relay and clickover.
2 lots of +/-44V dc off the main ps and 23,19,19,23 Vac on the minor
secondaries.
So next to check the minor DC rails and whether the preamp is working.
Looking more like something silly like a child-proof lockout via some
set of keypresses or something like that. But nothing like a key symbol
appearing in the display.