Reduce Scan Size on a Video Monitor?

[Clive Tobin]

Back in Ye Olde Tymes the tube sets used to have Width slug-adjusting
coils, as well as pots for Height.

New stuff seems to have no adjustments whatever for Width, and only for
Height if you are lucky.

I would like to be able to eliminate overscan on some monitors, to see
the whole video signal. I have one supposedly Underscan-capable monitor
that still does not show the corners of the video. Underscan monitors
are harder to come by and expensive.

What part does the factory select to adjust the width? Can you stick a
coil or resistor in series with the yoke winding to reduce the width?
Will any of this mess up the geometry, disturb the high voltage, or
result in a frantic call to the fire department? Thanks.

 

Clive Tobin <clive@webband.com> wrote:

Can you stick a coil or resistor in series with the yoke winding to
reduce the width?

I saw an illustration to do exactly this in a Don Lancaster book. (The
original Secret Money Machine - it was used as an example of a sketch
vs. a printed illustration). Cut one wire to the yoke and add a coil
in series, that can be shorted out by an SPST toggle switch when not
required. I _think_ it was just on the horizontal but I don't remember.
I don't have the book anymore and I don't remember the specs on the coil.
This probably applied to a garden-variety TV set of ~1980; it may not
work as well on a 1600x1200 VGA monitor.

I know that when line voltage is low, the image on some sets shrinks.
If the set B+ is adjustable (with a pot), maybe turn that down and see
what happens?

Matt Roberds