James,
The neon, DB1219, should stay lit for a bit of time after turning the unit off. By going off fast, that sure sounds like your main filters are bad. In these in my 7000 series, I used Nichicon LGR 1200mfd 250V to restuff the cans. I also replaced the 150,000 ohm 1W with 100,000 ohm 5W, mounted off the board a bit to allow for more air flow around it, to bleed the B+ faster. With the new guts, the neon takes 30 seconds to stop flashing after turning it off. Check the B+ across the cans or across the 150,000 ohm 1W resistor. It should be 310V nominal. If about 280V or lower, the cans are going/are bad. In mine, I put in a CL60 or 70 off the mains to reduce the inrush current further. Being 50 years old, it would be best to recap the piece. Higher value electrolytics will work - especially on the 50V supplies (raise from 8,2/10mfd to several times the amount of capacitance and use 100V like Nichicon UHE). The originals are likely 60-70V. For the 17V supplies, use 35V. For the 15V lines, 25V. For the low value caps, 1, 2,2mfd for example, I used film types. I did raise the wattage of some resistors in the scopes.
I wonder if you still have the oily grime in areas that are a resistance path causing the crackling sound. The boards and other areas can be cleaned with ammonia or some detergent like Dawn, rinsed with warm water then left to dry for a while. A fan blowing on the pieces and/or over a heat register from a floor vent overnight. The dry heat that long will dry enough.
There could be a gap where the ultor lead goes in the glass at the front of the crt. If so, RTV works to seal that.
Mark
