Tech: Major Havoc adapter board.
Michael Wiener
Is the adaptor board required to run this game.
And, how do I get around using it?
Thanks,
Mike
mik...@aol.com
Clay Cowgill
In article <01bc00d3$e2c82c00$a212b8cd@mikey-s-c-puter>, "Michael Wiener"
<mik...@aol.com> wrote:
Not required, it just correct for display "bowing" on a Wells Gardner
Color XY monitor. You can use the X/Y outputs directly off the board if
you can live with the "bow" on the screen.
I'm working on some replacement "display corrector" boards now, but it's
got cold in the garage and I haven't finished yet. (I have a real ugle
one bread-boarded up on my Star Wars though... ;-)
-Clay
Clayton N. Cowgill Engineering Manager
_____________________________________________________________________
/\ Diamond Multimedia Systems, Inc. cl...@supra.com
\/ Communications Division http://www.supra.com/
Jess Askey
Michael Wiener wrote:
>
> Is the adaptor board required to run this game.
> And, how do I get around using it?
> Thanks,
> Mike
> mik...@aol.com
The adapter board (either from Space Duel/Gravitar or Tempest
conversion) is used mainly for two
reasons.
First, so that when doing the conversion you could use the existing
wiring harness and not
have to mess with re-wiring and jumpering.
Second, to correct the X-deflection output. Space Duel, Gravitar and
Tempest all used Wells-Gardner
monitors, while the dedicated Major Havoc game used the amplifone. Im
not sure of the exact reason
but the Wells-Gardner monitors have a pincusion effect on a linear
input. Because of this there was
corrective circuitry on the game PCB's of SD,G and T. These are
analog multipliers that correct for
this non-linearity. Since Major Havoc used the Amplifone, none of the
analog multipliers were needed.
No big deal, but if you run a Major Havoc game PCB on a Wells-Garner
monitor you will have some pincusioning(arched in top and bottom,
looking at a drawn square box, such as self test). The adapter
board contain the necessary circuitry to remedy this. But to tell you
the truth, when the game playing
it is hard to see any effect from this pincushioning.
Any additions Clay??
Later!
--
Jess Askey Atari Game Page:http://magenta.com/havoc
The Audio Analyst
509 S 2nd St Unit B Wanted: Atari I,Robot PCB
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(307)721-9001 Atari Quantum PCB
Clay Cowgill
> Second, to correct the X-deflection output. Space Duel, Gravitar and
> Tempest all used Wells-Gardner
> monitors, while the dedicated Major Havoc game used the amplifone. Im
> not sure of the exact reason
> but the Wells-Gardner monitors have a pincusion effect on a linear
> input. Because of this there was
> corrective circuitry on the game PCB's of SD,G and T. These are
> analog multipliers that correct for
> this non-linearity. Since Major Havoc used the Amplifone, none of the
> analog multipliers were needed.
> No big deal, but if you run a Major Havoc game PCB on a Wells-Garner
> monitor you will have some pincusioning(arched in top and bottom,
> looking at a drawn square box, such as self test). The adapter
> board contain the necessary circuitry to remedy this. But to tell you
> the truth, when the game playing
> it is hard to see any effect from this pincushioning.
>
> Any additions Clay??
Nope. Well put. ;-) I'm not sure if the Ampliphone has the correction in
the yolk response or on the deflection board somehow. It looks like
Cinematronics might have solved it by using a smaller section of the
"sweep" developed by the analog integrators, although they also have some
funky analog stuff in there as well. I guess Atari used more expensive
caps to try to get a more linear charge curve.
At any rate, the WG monitor will "bow" as Jess describes unless a
correction board is used. I've got a breadboard version of the correction
board working (mostly) in my garage, but I've yet to produce any PCB's for
it...
Zonn
cl...@supra.com (Clay Cowgill) wrote:
~ In article <32DA9A...@magenta.com>, je...@magenta.com wrote:
~
~ > Second, to correct the X-deflection output. Space Duel, Gravitar and
~ > Tempest all used Wells-Gardner
~ > monitors, while the dedicated Major Havoc game used the amplifone. Im
~ > not sure of the exact reason
~ > but the Wells-Gardner monitors have a pincusion effect on a linear
~ > input. Because of this there was
~ > corrective circuitry on the game PCB's of SD,G and T. These are
~ > analog multipliers that correct for
~ > this non-linearity. Since Major Havoc used the Amplifone, none of the
~ > analog multipliers were needed.
~ > No big deal, but if you run a Major Havoc game PCB on a Wells-Garner
~ > monitor you will have some pincusioning(arched in top and bottom,
~ > looking at a drawn square box, such as self test). The adapter
~ > board contain the necessary circuitry to remedy this. But to tell you
~ > the truth, when the game playing
~ > it is hard to see any effect from this pincushioning.
~ >
~ > Any additions Clay??
~
~ Nope. Well put. ;-) I'm not sure if the Ampliphone has the correction in
~ the yolk response or on the deflection board somehow.
By extending the neck of the CRT, Amplifone lowered the distance_to_center to
distance_to_outside ratio allowing for less of a bowing effect, they then glued
little magnetic strips of metal to strategic spots on the yoke's perimeter to
help linearize the display.
~ It looks like
~ Cinematronics might have solved it by using a smaller section of the
~ "sweep" developed by the analog integrators, although they also have some
~ funky analog stuff in there as well.
Cinematronics used a diode/resistor ladder in the feedback of their integrators
to compensate for the yokes greater effect on the outside edges of the CRT.
Using the a smaller section of the "sweep" allowed them to draw straight lines
*anywhere* on the screen. Since the charging of a capacitor in an integrator is
non-linear, they chose the most linear section of the charge curve to be used as
the "vector".
~ I guess Atari used more expensive
~ caps to try to get a more linear charge curve.
Perhaps, but that's not the reason for "bowing", this is caused by the yoke's
greater effect, on the CRT beam on the outside edges of the CRT. This is
because of the longer distances traveled by the electrons as they flow from the
CRT guns, to the outside edges of the CRT, as opposed to the center of the CRT.
The greater distances give more time, for the yoke, to effect the path of the
electrons. You end up with bowing, and if not corrected for, the images
displayed will grow in size as they approach the edges of the CRT.
Atari chose multipliers to correct for the bow, and VDRs to correct for the
image growth and ended up with the nicest picture of the lot. (IMHO)
~
~ At any rate, the WG monitor will "bow" as Jess describes unless a
~ correction board is used. I've got a breadboard version of the correction
~ board working (mostly) in my garage, but I've yet to produce any PCB's for
~ it...
I look forward to it!
-Zonn
Clay Cowgill
> Atari chose multipliers to correct for the bow, and VDRs to correct for the
> image growth and ended up with the nicest picture of the lot. (IMHO)
So *that's* what the VDR's are for. I've never got a definitive answer on
that before. Any idea what kind of values those VDR have? I've never
found them described...
Thanks!