There are a few hi ohm 2W resistors in the focus on the fiber FBT board IIRC.
Check them 1st. Also the spark gaps in the CRT socket can short. Just
unhook the focus wire & see if the F at the chassis comes up to 5-7 KV.
If it goes beyond that I will pull the manual if I got it.
BTW FBT's on most tube color sets will kill the raster & give little or no
HV etc.
73 Zeno
LFOD !