"James Sweet" wrote in message
news:q1N9i.6545$UD4.952@trndny07...

"Peabody" wrote in message
...
In article YSH9i.8670$fX4.7651@trndny03,
says...

And I wonder if I could do this by adding additional
inductance in series with the horizontal deflection
yoke, with the idea that more inductance would slow
down the rate of change in the yoke, so that the beams
don't progress horizontally as fast as before, and
therefore finish the line before reaching the edge of
the screen.

Usually that's precisely how it's done. Look for an
inductor in the horizontal section with an adjustable
slug, it may have enough range to do what you want
without even modifying anything.

I don't see anything adjustable. There's a big IC that
produces an "HD" output, which goes to the base of the
Horizontal Drive transistor (NPN), the collector of which
connects to the Horizontal Output transistor by way of a
transformer. But there's nothing on the schematic
suggesting anything is adjustable.

Any idea what kind of coil I would need to add? How many
turns? What gauge wire?



It's usually a coil about 1/2" diameter and an inch tall wound with what
looks to be around #14 Litz wire in series with the yoke. If you can find
an older junk TV you could probably salvage something.


Is there not a set HT pot in the power supply ? Usually, turning this down
by a few volts will shrink the picture all round. You can then just correct
the vertical via the menu. I would not personally try adding inductance into
the H-OP stage or scan coil path. This is a very stressed and very carefully
designed bit of circuitry, and some extra L that it doesn't want, could lead
to all sorts of unwanted effects such as ringing, poor linearity, or even
overheating and ultimate failure of the H-OP transistor. If you were to
start adding L, then you would probably also have to alter the value of the
S correction cap in series with the scan coils, as this forms a tuned
circuit with the scan coils to deliberately make them ring in order to
achieve the velocity modulation of the beam required to get a linear sweep
on a flat(ish) tube face. I'm actually surprised that you feel that you have
that degree of overscan that it's affecting your viewing. If you really are
missing actual picture, then it must be significantly more than the 'normal'
7 - 10% raster overscan. Remember that the broadcast picture is not as wide
as the scanned raster, and a lot of the relationships that we used to use to
judge picture width, have now gone out of the window, with all the different
'widescreen' formats that they keep broadcasting now, and which many older
TVs just don't look good on. Have you actually looked at the picture on a
proper 4:3 test pattern ? It's the only way really to make a valid judgement
on the picture geometry. You may of course have an actual fault. It's not at
all uncommon for the values of the components in the set HT circuit to
drift, resulting in a slowly 'growing' scan.

Arfa