Gordon,
You could have the black slick slime that is on the ceramic part of the funnel on the crt. I have seen this before. That will cause a leakage path and possibly corona. Clean the high voltage area. There is most likely black dust there. I used ammonia and a brush to clean this area, rinsed then let dry. The carbon resistors there could be bad. The arcing could be one or more opening internally. I have had ones like this break as soon as a leg is unsoldered then lifted enough to be away from the place it was soldered to, not bent back enough with force to stress the body.
The high voltage regulation could be off due to R803 being overstressed. I put a 5W in mine. C802, C806 and C802 could be bad. The first two, if replaced, should be a PP type at 600/630V. The high voltage pot wiper could be dirty. Turning it back and forth several times will help as this is a sealed 2W pot. Sometimes the 500mmfd condensers in the high voltage will get leaky. The 453/4 series have this problem.
You may have a bad tunnel diode, D85, in the B sweep. Check the waveform at the junction of D59 and D85. Condensers C76/276 could be open. These two I used ULD types. A 50/63V film such as a Wima could be used. These two original electrolytics were open in mine. You could have leaky 'holdoff capacitors' in the timing circuit. The red body ones I replaced in mine.
The ripple on the 350V supply sounds like any/all electrolytics in that supply are going bad, C701, C730 and C709A. The ,01mfd condensers from the regulated outputs back to the grid of the control valve are known to go bad. These are an automatic replacement when I work on this type of supply after seeing enough bad ones over the years. The cans in the supplies can be restuffed with larger values, e.g. 100mfd to 150mfd. Ones like Nichicon LGR series are great replacements for the larger value and voltage types and ULD/UCY for the lower values such as 10-40mfd.
In mine, I put in 1% tolerance resistors with only a few 5% in areas where the tolerance and 200ppm/deg C would be fine. I restuffed cans. I did find a number of resistors that should be increased in wattage. I was glad I spent the resources after seeing the results. I know it is a labour of love.
Mark
