Is there any way to stop the glowing dot ?
 

I have two 60s zenith sets and they both have the glowing dot with halo after shut off , is there any way to prevent the set from doing this ?
I know if you pull the socket off the CRT and then shut down it won't do it , thought of putting a switch on the filament wire and just flicking it before shut off but there must be a better way.

Period mags had articles on this. IIRC the mod was a cap and one other part added to the circuit...In your shoes, I'd go to American radio history and go through the indexes of the mid 50's Radio and TV news mags to look for the article.

A few sets had a "spot killer" switch built into the on off switch but
Zenith never did. Its part of the charm of an old TV ! Check the
G-1 CRT voltage, there may be something off making it
worse. Other than that the HV will stay charged & cathode stay
hot & emit electrons. Probably a switch to ground out the G-1
at turn off may stop it. But it is normal. Even a lot of color sets
will do it. Growing up we had about a 21" Zenith in our room. With
the lights out that thing would glow for hours although it would
spread out & slowly dim.

73 Zeno:smoke:
LFOD !

It's not the filament you want to kill. You really want to discharge the HV.

Some sets may do this by drawing a lot of cathode current while the raster is still collapsing (somehow the cathode voltage collapses faster than the G1), so you get a momentary bright flash as the raster collapses and no long-term spot. Sets with focus dividers will discharge the HV through the divider.

Motorola's first solid state monochrome chassis had a spot killer that worked when the power switch was turned off, but they didn't think of the case of someone pulling the power cord with the set running. Pulling the power cord was SOP at the end of the production line, and the cathode voltage, derived from the flyback and having no bleed path, stayed up so long that the spot formed many seconds later and burned a spot in the center of the screen after the set was boxed. This was not discovered until sets were unpacked after shipment. A quick fix had to be added to the chassis so that when B+ collapsed, it would pull down the video supply.

In the end, I agree that if a defocused spot is normal operation, you should just enjoy the nostalgia.

Ok I will leave well enough alone , I just was worried it would burn into the phosphor .
It's not the best CRT as far as emissions , it's on the weak side but delivers a nice picture and plenty of blacks , thr dot and halo do last a while compared to a 19" with a really good CRT from the the year before , it's dot and halo doesnt last long and the 23" I grew up with was either a 61 or 62 never had a dot or halo and neither did the 19" from 61 with the tube remote .