THE SETSymptom: Search: Solution:chassis in your CT-100 will require newborn-like attention to care, calibration, and overall healing therapy. This anomaly is unaffected by brightness or contrast control setting. The effect was still visible with the brightness and contrast controls fully counterclockwise. Sharply defined edges of the anomalous shapes coupled with the very solid colors suggest dc coupling rather than RC network involvement. In other words, it 'looks' like a short; it is not characteristic of a video signal being processed by amplifiers and reproduced on the screen. A look at the schematic shows two possibilities. Either the 15GP22 is intermittently shorting internally somewhere, or the 6BC7 triple-diode that serves as the dc restorer is shorting. Light tapping of each tube during an episode does not aggravate and therefore pinpoint a perpetrator. Solution: I replaced the dc restorer, but unfortunately the problem has recurred. T'shooting continues... [1-15-2006 update: unfortunately, the consensus is that the CRT is the source of the problem. Fortunately, it has been three weeks since the last episode. Case closed for now.] [12-27-05 Pete Deksnis]
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