The CRT bell is a big capasitor. One plate is inside the CRT & hooked
to the HV lead. The glass is the dielectric. The dag is the other plate
of the cap. Without the dag the HV is unfiltered & instead of DC the HV
will be pulsating.
You can recoat it but MUST follow the old pattern.
The dag usually goes to chassis ground via a long spring across the dag.
If much of the dag is missing you may get arcing, hissing & ozone smell.
HV will also be reduced. The other thing is if the dag is flaking off the
flakes fall onto the chassis & can cause shorts.
73 Zeno
LFOD !