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NotTaR of Television Sets : Bad CRT causing retrace lines
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(From: Jeroen H. Stessen (Jeroen.Stessen@philips.com).)
The TV which I bought last started developing retrace lines after a month or
so of use. I took it back to the lab for warranty (special deal) and had it
examined by the real experts. They found that even with the filament supply
disconnected and VG2 at 0V the screen would still light up. They could even
see that the electrons weren't even coming from the cathode. That was with
only the picture tube in a test rig. So in this case the obvious conclusion
had to be that the tube was bad, and it was replaced (32" 16:9 SF, very $$).
It had something to do with processing problems during manufacturing of the
electron guns.
So even if this was a rare case, it CAN happen that retrace lines are due
to a bad picture tube. It's more usual to suspect the VG2 (screen voltage)
or a defect somewhere in the RGB video path.