RE: Noticed new vector monitor discussions, this is my input...

>Wouldn't it just be simpler to intercept the
>signal to the deflection amps and insert the
>vector signal there?

That's what I first thought until I looked at a schematic on
a raster monitor. They use oscillator circuits instead of deflection
amplifiers. The drive voltages would way too low for fast movement
on the y axis too. A lot of this has been discussed already,
but it's good to re-think to make sure we're on the right track.
============================

-----Original Message-----
From: owner-vectorlist@lists.cc.utexas.edu [mailto:owner-vectorlist@lists.cc.utexas.edu]On
Behalf Of Matthew Sell
Sent: Friday, October 22, 1999 11:37 AM
To: vectorlist@lists.cc.utexas.edu
Subject: Re: Noticed new vector monitor discussions, this is
my input...

  
Wouldn't it just be simpler to intercept the signal to the deflection
amps and insert the vector signal there?
A daughter-board for an exisiting monitor could then be made
that has the proper connector for the vector game, and place
simple protection and spot killer circuitry on it.

This way an exising monitor could be used, with simple trace
cutting and soldering of wires from a daughter board to the existing
monitor board, and installation into the game.

Thoughts? It would probably be much cheaper than replacing the
yoke, assuming of course that the existing yoke could handle
that form of deflection.

    - Matt
  
  
  

James Nelson wrote:

Thanks for your input. Here are some comments on it: >...winding
your own yoke may well be almost impossible... I agree and I
plan to have them done by a standard yoke winding company. >...electronic
pin correction... Thanks for mentioning it. If pincushion is
a problem, I can inject some of the y signal into the x drive.
 I'll probably put a trimpot in for this adjustment. I noticed
that some of the 19" units seem to do this with one or two turns
on a separate winding too. I need to take the time to understand
what Clay's display corrector is all about too. http://www.multigame.com/display.html
>...double the drive-use 2 driver boards, and 2 sets of outputs...
The topology and devices are all wrong for that use, especially
the way you described using them on each side of the winding.
 They use the ground side for feedback, and feedback is what
will get you in trouble every time with this. The closest thing
you could do that would to beef up the drive wouldn't require
a second control board at all: Just get an extra set of identical
transistors, put it them parallel, with the first set, and connect
the outputs of each through a resistor like 1 ohm, 3 watt. >How
about boosting the voltage to the board?>The driver bias could
be adjusted to compensate,>and getting hi-power transistors at
6 Amps and>200 Volts are possible now. I don't quite understand
what the voltage increase is supposed to accomplish. You can
try this right away by bypassing the voltage regulator transistors
on your power supply. In fact, there is an evil tech document,
http://www.gamearchive.com/video/manufacturer/atari/vector/monitors/wg_color/final_solution.txt,
that someone actually reccomended this. (What were they thinking?)
The power dumped across a transistor (or any device) is going
to be precisely equal to the voltage across it times the current
through it. The current, in a correctly working drive, at any
given moment will be the same no matter what the voltage input
is becuase the current is what is fed back. The conclusion to
draw here is that you want the voltage to be as low as you can
make it so that you are just above the threshold of degrading
performance. Increasing the voltage would be desirable only if
you couldn't get enought deflection or your draw speed was being
limited (warped vector draws). In your case, where you are going
to make a custom vector game from scratch, maybe higher voltage
would be good, but I wouldn't do it ever unless the monitor couldn't
keep up with the game. By the way, I think those existing transistors
are 10 amp 100V devices. Good enough on paper. Have a nice day,James====================================

----- Original Message -----
From: Aaron Howald
To: vectorlist@lists.cc.utexas.edu
Sent: Friday, October 22, 1999 2:49 AM
Subject: Noticed new vector monitor discussions, this is my input...
 Hi to all of you! Since I work on TV's for a living, I thought
I'd add my input to the fray... Firstly,I think winding your
own yoke may well be almost impossible. Unlike a standard coil
(like a relay) the windings are staggered, crossed over on each
other in a wild fashion, and precisly placed. All of this is
for convergence assist+pin correction on some yokes. Doing this
by hand is a grisly task, at best!Second, some obsevations on
standard tv yokes. 13" tv's NEVER have any electronic pin correction
at all. I assume this is because of the small screen size...
19" sets generally do not either, but most 25" do, and 27"-up
ALWAYS have the correction. I assume with larger max deflection
angles+longer beam travel, it becomes a nessessity. There is
1 25" set I know of that has no correction, and looks fine-other
sets use a complex board to do it...but I wonder, if the yoke
can be wound to fix the pin, why use a more expensive correction
board? Third, I thought of an easy way to double the drive-use
2 driver boards, and 2 sets of outputs! Drive board 1 (say a
P327 from a WG) is X only, 2nd for Y. Feed drive 180 deg out
of phase to one input, and connect the yoke winding between
the 2 outputs. Has anyone tried this? I'd like to, but I need
a P327 WG defelection board. Anyone have one for sale?! The
yoke would have 2X the "kick" on it, for 2X beam draw speed.
DC hold current would be the same, but drawn from both supplies
(+-) equally (at 1/2 voltage each Of couse 2X parts=2X chance
of failure! How about boosting the voltage to the board? The
driver bias could be adjusted to compensate, and getting hi-power
transistors at 6 Amps and 200 Volts are possible now.I'm still
working on my game system-slowly. It will be awsome when done-A
modded 19" WG with a vector drive board of my own design,
with a computer driver program/game engine of my own design.
If I can get a deflection board, I am keen to try the board doubling
idea and the voltage increase.Keep up the stimulating conversation!
 
Aaron Howald
ahowald@w-link.net

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