The Family DuMont

[Phil Nelson]

Originally Posted by jr_tech

Sometimes I have observed, when re-installing a round P-4 CRT after work on the chassis, that orientation of the CRT is critical otherwise "blueish" areas of the CRT are illuminated.

That reminds me, I saw that effect when I reinstalled a CRT in my RCA T-100. What's causing those faint blue areas on opposite corners, I wondered? Then I realized that if I rotated the tube and reduced the height to normal, they would exactly match the areas never scanned by the electron beam. The center portion that had been scanned was warmer in color.

The color difference was subtle. It didn't really register in a photo unless I cranked up the contrast & brightness beyond normal levels, high enough to make retrace lines.

Phil Nelson