WHAT YOU SEE IS WHAT YOU GET ?
By G8MNY
Camera View finders often lie about what you framed the camera on.
Height is normally set by a preset pot, but the width is factory component
set.
There are 2 ways of width adjustment.
1. Change the tuning capacitor across the line output transformer. Reducing
it's value will reduce the scan width, but it will increase EHT, (tube
heaters?). But sometimes this is the only option. This method does speed
up the flyback time and can stop picture wrap-around at the edges on slow
flyback designs. Careful selection of value and type of capacitor is needed,
as a failure could blow up the line output transistor, EHT tripler, line
output
transformer etc.
2. Increase the inductance that is in series with the scan coil, by adding
one or modify the existing inductor. On linearity corrected line scans
designs, there is a magnet biased inductor to correct for the one sided
saturation that occurs on the line output transformer. On large TVs (and
Computer Monitors) this parameter may be adjustable both in inductance
(width) and magnet strength (linearity). But modern small and miniature
designs use fixed production selected values or non at all.
Option 2 is the the simplest to try first.
Adjustment of the inductance can be done by;-
a) adding external ferrite pieces,
b) adding tiny bias magnet to alter the cores magnetic properties.
c) adding or removing a few turns,
In practice for a) & b) a section of rubber sleeve around the inductor
to hold on a piece of magnet or ferrite is all that may be required.
With both 1 or 2 option, locating the components concerned may be difficult
and a diagram and layout might be needed.
|
