HV Arc on CTC-5

[TVBeeGee]

Any advice on high voltage arcs on a CTC-5? I have not yet measured the HV on my "new" CTC-5, but it has arced once and we assumed this was due to a combination of dirt and humidity. (The chassis has been recapped some time ago by a different owner.) In addition to a thorough cleaning of the chassis and especially the HV cage, would it also be a good idea to remove and clean the area between the CRT and its plastic insulator, or is this area normally sealed enough to prevent dirt and moisture from getting in? I do not plan to power the set again until I have protected the HV from arcing. After the arc occurred, we still had horizontal sweep and high voltage, but vertical deflection was missing. I don't know if the missing vertical sweep was related to the arc. Could be a different problem, even a bad tube socket. The set was working fine before this attempt to power it, which caused the arc during warm up. The set had been sitting in a garage for some time before this attempt to power up.