Re: New Vector monitor project progress : YOKES

IF the inner winding is the horizontal axis (it very well may be) it
may be usable as-is. The high inductance winding of a raster yoke
is the vertical one. TV yokes seem to run around 30 mH, VGA
monitor yokes are closer to 5 mH.

NASTY MATH DEPARTMENT: Assuming you want to move
the beam from the center to an edge in 150 uS AND it takes 3
amps to do that a 5 mH yoke will need 100 volts of drive (plus
whatever is lost in the coil resistance) to work. The 30 mH part
will need 600 volts. A 1 mH coil will need 20 volts.

Now that assumes a LOT! The lower the inductance is the higher
the current to deflect the beam will be. So the numbers above are
pulled right out of clear air and have nothing to do with the real
world.

Another interesting thing, though, is that magnetic field is
proportional to the number of wire turns, but inductance is
proportional to the SQUARE of the number of wire turns.
Cut the number of turns in half and the current you need will
double but the inductance (and the voltage drive) will be one
quarter. Vertical yokes are usually wound with the two halves
in series. Reconnecting them in parallel effectively cuts the number
of turns in half, inductance by a factor of 4, drive current doubles,
and drive voltage drops to a quarter.

So a VGA monitor yoke looks ALMOST useable. However, I
priced a 19" VGA tube with yoke and was told I was in for over
$600! Once you go back to a regular tube with a VGA yoke the
price would get reasonable, BUT that combination isn't offered as
an off-the-shelf part.

Clay Cowgill wrote:

> > I thought of hand winding, but I wouldn't want to wind that inner
> > yoke winding. Take a look at one. I can't be done by hand,
> > unless you had a custom form and epoxy dip for winding. I might
> > entertain winding the outside coil by hand, for testing or in
> > a fix.
> >
> I was thinking more along the lines of the thicker amplifone-like windings
> for both axis. Those looked possible to hand-turn to me. (But then again,
> I'm not keen on trying it. ;-)
>
> -Clay
Received on Wed Oct 20 13:38:57 1999