Actual purpose of dag coating?

[CJVx]

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.

[ARC Tech-109]

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

[CJVx]

Originally Posted by ARC Tech-109

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?

[zeno]

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 !

[Alex KL-1]

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

[Electronic M]

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.

[Yamamaya42]

Originally Posted by Electronic M

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?

[ARC Tech-109]

Originally Posted by Yamamaya42

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

They could be yours if the price is right

[TV-collector]

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