(From: Bert Christensen (firstname.lastname@example.org).)
|NotTaR of Television Sets : Comments on vertical problems
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<< Vertical foldover |
| Jagged or uneven vertical.. >>
As a general rule, vertical faults can be divided into two types: ones that
cause geometric distortion (a circle will not be round) and those that simply
black out a portion of the screen. The former are faults in the vertical
oscillator, drive, or output stages. The latter are blanking faults. Blanking
faults are almost always caused by electrolytic capacitors changing value and
thereby changing the timing of the pulses which blank the screen during
vertical retrace. In other words, the pulses are turning off the video signals
at the wrong time.
The most common true vertical fault is geometric distortion and a foldover of
white lines at the top of the screen. This is almost always caused by the
electrolytic capacitor on or near the collector of the vertical output
transistor or part of the IC which has the supply voltage (B+) on it. In the
old tube days, the general rule was that bottom distortion was in the cathode
of the output tube and distortion at the top was caused by a fault in the