I made/ obtained some extension cables to run the chassis with the CRT. I powered up the set with the CRT and the sweep circuits appear okay apart from minor vertical non-linearity. All the paper caps on the vertical sweep board have been replaced and since the height control is at it's limit, I suspect the 2.2Mohm oscillator plate resistor has drifted. I will investigate later.
The brightness control functions correctly at turn on but in about five minutes, the brightnes increases. I found the negative voltage for the brightness control drifting upward (towards positive). The negative voltage is obtained from the horizontal output tube grid leak bias and the 470kohm resistor coupling to the brightness control bad. So far so good.
I have been tracking down an intermittent corona from the HV cage. I used a long piece of plastic heat shrink tubing as a listening tube and tracked down the corona to the focus pot. I shall take this apart and investigate. I suspect the focus pot is troublesome in these sets.
I fed an RF modulated rainbow pattern to the antenna and see video of sorts on the CRT. Contrast is low and picture is washed out: I shall go through the video chain later.
Following the discussion on CTC5 low HV, I measured this set's HV at about 23kv. (I measured the HV with the Heathkit VTVM and HV probe I bought new in 1971!) I am pretty sure the calibration is still reasonable as I have recently compared other sets HV measurements. The measurement tolerance I would put at no more than +/-1000v.
In any case, the raster on this set is brighter than I would have expected for a 21AXP22A. It is bright enough to watch in a typical evening lamp lit living room although it may be tough to watch in a sunlit room if the curtains aren't drawn.