For all the seasoned CRT techs, I have a question I think I know the answer, but wanted to confirm.

I was working on an Arcade monitor and had issues with the flyback and CRT focus. It was making a slight arcing sound, so I replaced the tube connector on the neckboard (CR-31) and flyback, which fixed the problem. Out of curiosity, I took the connector apart and wanted to know how the focus part was connected and if the following is the spark gap for the focus.

Picture 1 - CR31 assembled, removed from neck PCB
Picture 2 - Bottom of CR31, the connector circled is soldered to the neck PCB ground plane
Picture 3 - CR31 disassembled
Picture 4 - Circled is the focus connector. On the top is where the ground connector from picture 2 comes into the CR31 and has a dip. Question is: is the reason the ground connector has a "dip" that about 5mm away from the focus connector plane for spark gap for the CRT focus? If so, I'm assuming being 5mm allows up to 15Kv before arcing and grounding the over-voltage.


Picture 1


Picture 2


Picture 3


Picture 4

 

Looks about right, as I can see burn marks from arcing where the e-field would be directed.

 

Certainly there are (were) CRT circuits that had to be protected from excess voltage, some voltages would cause internal arcing that damaged the CRT, while other over-voltages would produce X-rays that were deemed unhealthy.