Re: Quasi-interesting CRT puzzler

In article <1155812670.217029.191880@xxxxxxxxxxxxxxxxxxxxxxxxxxx>, grg2
@comcast.net says...
Okay, this is kind of a retarded question, but here goes.

Let's say you want to convert you basic PC monitor from raster scan to
vector.

You pull off the yoke connector from the main board and find out the it
still runs okay, well except that you've burnt a little spot of
phosphor in the center of the screen unless you were prescient enough
to back off the brightness, contrast, and the three screen controls
first.

Then you hook up a DC supply to the V and H yoke coils and find out it
takes about 3 AMPS to do a full screen deflection in the vertical
direction, about TEN amps in the horizontal direction.

(I think that's because the horizontal deflection has to happen faster,
therfore lower inductance in the h coil, therefore fewer gausses per
amp).

So we need some pretty hefty drivers, many amps plus many volts if we
want fast deflection.

Not a huge problem so far.

But now we realize we don't want to burn the screen if we're drawing
short or slow vectors, and we don't want the lines to be invisible if
we're drawing them long or quickly.

So we need some sort of Z-axis brightness modulation, somehow
proportional to the "writing rate", like in inches per millisecond or
thereabouts.

Anybody have any idea how to compute this on the fly as it were?

Ideally I'd like to be able to draw 6000 full length vectors per
second.

A quick web search didnt find anything promising.


Regards,

George


Get a few schematics for the old WellsGardner Color XY monitors used in
the likes of Atari Tempest and so on.
They basically had a deflection coil that was symetrical for the X and
Y, used identical X and Y deflection circuits and used the amplitude of
the drive circuit to handle the bigger X than Y (yes it could drive the
guns off the edge of the phosphor). The guns were driven just like they
are in a raster scan system just with the addition of a "Spot Killer"
circuit that would kill the guns if there were no X or Y deflection,
keeping you from burning a hole or line in the phosphor.
The X and Y amps look a lot like a beefed up audio amp.

Jim
.

Relevant Pages

  • Re: Quasi-interesting CRT puzzler
    ... You pull off the yoke connector from the main board and find out the it ... about TEN amps in the horizontal direction. ... (I think that's because the horizontal deflection has to happen faster, ... somewhere to take it off the signal path before the coil drivers. ...
    (sci.electronics.design)
  • Re: Quasi-interesting CRT puzzler
    ... You pull off the yoke connector from the main board and find out the it ... about TEN amps in the horizontal direction. ... (I think that's because the horizontal deflection has to happen faster, ... But now we realize we don't want to burn the screen if we're drawing ...
    (sci.electronics.design)
  • Re: Quasi-interesting CRT puzzler
    ... You pull off the yoke connector from the main board and find out the it ... about TEN amps in the horizontal direction. ... (I think that's because the horizontal deflection has to happen faster, ... But now we realize we don't want to burn the screen if we're drawing ...
    (sci.electronics.design)
  • Re: Quasi-interesting CRT puzzler
    ... about TEN amps in the horizontal direction. ... (I think that's because the horizontal deflection has to happen faster, ... Tuned deflection coils, ... The energy stored in the inductor provided the high voltage ...
    (sci.electronics.design)