[sdiy-interim] first commercial video module?

[ChristianH]

On Wed, 28 Mar 2007 12:31:39 -0400 "Roy J. Tellason" <rtellason at verizon.net> wrote:

> On Tuesday 27 March 2007 20:03, Paul Perry wrote:
> > Back in the Good Old Days, one converted a TV to a crap
> > oscilloscope thusly:
> >
> > Take a line out from the horizonal scan.
> > Take a line out from the vertical scan.
> 
> I always wondered how they did that without messing up the high voltage,  
> which is typically derived from the horizontal sweep...

IIRC, the deflection coil usually is coupled via a separate output
winding of the line transformer. So I guess you could remove the coil
from the transformer and feed it with other signals without disturbing
the tranformer/hi voltage generation too much.

But for some fun, it's possible to just play with the vertical coil, and
let the horiz scanning run as usual. That's what I did back then.
Aah, those were the days... Imagine kids, you could actually obtain a
schematic for a TV set :-)

I wouldn't be surprised if in today's CRT TV sets the line and vertical
frequencies were software generated, which would make things a bit less
obvious.

Christian


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