Actual purpose of dag coating?
 

I looked around and couldn’t find an actual described purpose of the coating. I ask because I have a few TVs with various states of missing dag, But don’t seem to have any operational issues, however, there is room for improvement. Wondering what I could be missing should I redo the dag.

Its the negative plate of the vacuum capacitor of the pix tube glass bell

All right, so what would happen should the dag not be present?

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:smoke:
LFOD !

Basically, old models using eg. metal coned CRT uses external capacitor (a "doorknob" type).

Slipplate is a good replacement coating. Generally you want to avoid dag islands as they can arc to each other and cause picture disturbance/video noise, and if arcing between islands (or between the dag and a poorly contacting ground strap) is constant and bad enough it can unevenly heat the glass and cause implosion.

dag islands ? aren't they just off the coast of Florida? :D

They could be yours if the price is right :yes:

If you have graphite dust / -flour you can mix it with wood glue and paint it with a paint brush on the right areas.
That advice came from my physics teacher in the 70s and it worked very well!
Please clean areas in question before.

Regards,
TV-collector:stupid: