monitor question (problem diagnosis)

[Jim Beacon]

From: "Barry Watzman" <Watzman at neo.rr.com>


> Re: " What does a single vertical line in the middle of a display
indicate?"
>
> This is a symptom that is normally never seen.
>
> It would, in theory, indicate loss of horizontal deflection.  The problem
is
> that loss of horizontal deflection in virtually all monitors also causes
> loss of high voltage, which keeps you from seeing ANYTHING.  [The high
> voltage is obtained from the horizontal output transformer ("flyback"
> transformer) in virtually every TV set and monitor made.)
>
> One possibility:  If the horizontal deflection yoke was open, there could
be
> a loss of horizontal deflection while you still had output from the
> horizontal output transformer.  Usually, an open yoke would shut down the
> horizontal output and high voltage, but it's the only way I can think of
> that you might get loss of horizontal deflection and still have high
> voltage.


Not in modern monitors! (in fact not for about 15 years in most "computer"
monitors)

The horizontal deflection is now normally divorced from EHT generation, due
to the large number of horizontal frequencies that the monitor must accept.

The EHT unit of a modern(ish) monitor has more in common with the RF EHT
generators of 1950s projection TVs, than of anything more modern.

Jim.