[Tomcomm]

After a few months activity on a couple of my 70s rectangle ss tvs I got back to my "custom installed" 21CT55. It had been ignored for about four months and I was curious if would come up with the same demonstrated picture quality it had before. It did after a 15min warm up and all was well.

I'm now running the AC power input off a computer power stabilizer and a big Powerstat so I can maintain the same voltage out of the silicon rectifiers that replaced the original selenium rectifiers. I adjust the Powerstat for a nominal B++ of 400v specified by RCA. This occurs with an AC input of 110vrms. Since I don't have access to an ultor HV meter probe I run the HV adjust fully cw max. At this setting I read a boost of 1010v! Nothing seems stressed, everything in the HV cage looks normal and the HOA 6BC6 has no plate glow or blue gas. I get very good focus and run the horz size at minimum. Gray-scale is near perfect, with very good PQ. RCA rates the
21FBP22 ultor at 27.5kv max. I may be exceeding this, but ignorance is bliss.

The only real problem I see with this operation is a very slight uniform screen glow in a totally black room with no video applied and the brightness, contrast and color fully ccw. No glow is seen at turn on and holds black for about 5min then ever so slowly starts becoming noticeable. This increases with time and becomes quite noticiable when compared with the Sony monitor after about 30min. I reduced the HV adj to min with no difference in glow.

I used my newly acquired Sencore CR70 (ebay $149) to check for element leakage that prevents complete gun cutoff, all read good. Cutoff on the CR70 all made the Good Box and all emissions were at half good meter reading. the lifetime test on each gun went into the bad zone when the heaters were reduced 25%. Seems like a good candidate for a mild Auto Restore. Only problem is the CT70 increases the heaters from 6.3vrms to 12.5vrms for 40 seconds during each gun test! That bright yellow heater glow scares me on such an old crt, so I'm reluctant to rejuvenate.

I would appreciate any comment on this cutoff glow phenomena and the advisability of submitting this really neat crt to unnecessary abusive. Tom