The first symptom was two pictures, one upside down,
separated by a thin white line which got smaller as the set
warmed up. The picture then went completely due to loss of
e.h.t. The line output and boost diode valves are glowing bat
the e.h.t. rectifier heater does not light up. There is line
whistle present, varying in pitch as the line hold control is
moved, so the line drive must be there.
There is a lack of boost voltage. Check the PL81 and
PY81 valves, the boost capacitor C93, the decouplers C89
and C91 and the boost smoothing capacitor C92 before
suspecting the line output transformer.