What is the difference between J-PAC and I-PAC?
The
I-PAC is a control interface which has all inputs connected into it via screw
connectors, for building your own panel and doing your own control wiring. The
J-PAC has most of the inputs connected to it via an integral JAMMA edge
connector and makes it easy to connect a standard JAMMA pre-wired cabinet by
simply plugging the cabinet connector onto the board. The J-PAC also contains
video circuitry for connecting the PC to the cabinet arcade monitor.
What is a JAMMA cabinet anyway?
JAMMA (Japanese
Amusement Machine Manufacturers Association) is a wiring standard which was
developed in the 1980's to standardize wiring of cabinets to game logic boards.
A JAMMA cabinet has a 28+28 way edge connector for connection to a game board
pre-wired to controls, monitor etc. If the controls you will be using are
not wired to one of these connectors then the I-PAC may be for you
rather than J-PAC.
What controls does the JAMMA connector support?
The
JAMMA standard supports 2 players with 3 buttons per player. There is an
unofficial addition to this, some cabinets wire a fourth button. Plus coin,
start etc.
Thats not many buttons, what about any others?
Game
boards which need more buttons have an auxiliary button connector which can
vary in type. This is not part of the JAMMA standard. The J-PAC caters for
these extra buttons by having screw terminal inputs for these extra inputs.
Inputs supported directly through the JAMMA connector are:
Player 1 and 2 joysticks, Player 1 and 2 buttons 1,2,3,4. Coin 1, Coin 2,
Start1, Start2.
Inputs supported by the screw terminals
are:
Player 1 and 2 buttons 4,5,6,7,8.
Note that button 4 can be
connected via either method as some JAMMA harnesses route this button through
the connector.
If you have a 4 player cabinet you can use an I-PAC2 board as
well as a J-PAC and plug the I-PAC into the pass-through connector of the
J-PAC. You will need to re-program the I-PAC board for correct player 3 and 4
keycodes.
Can I program the inputs?
Yes the J-PAC uses the
same programming utility as I-PAC. It also contains the connector for the I-PAC
LED harness.
What about video?
The J-PAC routes VGA video from
the PC VGA card to the JAMMA connector and therefore to the monitor. But of
course it's not that simple! There are configuration issues when using arcade
monitors on a PC with a normal VGA card (as opposed to our ArcadeVGA card). The
VGA card must be told to output a horizontal sync frequency which is much lower
than the VGA standard. The J-PAC amplifies the VGA 1 volt signal level to
approx 5 volts peak-peak which is the arcade monitor spec.
What does the J-PAC video circuitry do?
Besides
amplifying the video level, the on-board video circuitry also synthesises
composite sync from separate H-V sync from the VGA card. The J-PAC has a jumper
which is set to the frequency that the monitor is designed for (most commonly
15Khz). The J-PAC will not pass the sync signal through unless it detects the
signal is at the correct frequency for the monitor. Some older types of 15Khz
monitor could be damaged if fed with a high sync rate. The J-PAC prevents this
happening. If the sync rate is not in range, the monitor is still powered up
and still has video passed to it but no damage can occur as the horizontal
frequency cannot be driven too fast without any sync present. IMPORTANT: It is
not a scan converter so you will have to configure the VGA card to send the
correct sync rate for the monitor OR you can use our ArcadeVGA card which will
drive a 15Khz monitor with no special configuration.
How does the J-PAC work with the ArcadeVGA
card?
The J-PAC and the ArcadeVGA card (see details under ArcadeVGA
heading) make perfect partners and give the easiest possible solution for
driving a JAMMA cabinet with a 15Khz monitor. The ArcadeVGA card plugs into the
PC and simply plugs into the J-PAC via the VGA cable. Then plug into the
cabinet harness and you should get a perfect picture right from boot-up with no
worries about configuring the VGA card to send 15Khz.
What about half-screen mode?
This is a feature of
the J-PAC which allows a stable picture to be displayed from a PC running in
31Khz (VGA) mode using a normal VGA card (as opposed to our ArcadeVGA card) on
a 15Khz arcade monitor. What actually happens is, as the horizontal sync
frequency is divided by two, there are two pictures displayed on the screen
side-by-side. This is NOT meant for serious PC application use! It is useful
for checking all is well with the boot process. It is usually possible to type
in DOS sucessfully for configuration changes etc. A Windows picture (or rather
two pictures!) can also be displayed for limited use. Some monitors/VGA cards
display this mode better than others.
What about sound?
The JAMMA standard is for only
one speaker, mono sound. This is one of the reasons the J-PAC does not contain
a sound amp. Other reasons are:
There is no readily available 12V supply.
Using the available 5V supply would not enough power.
Using a separate mains
adaptor would create issues with local line cord types.
How do I wire for sound?
There are several easy
ways to do this:
Use a sound card with an on-board amp. Either wire this to
the speaker connectors on the J-PAC to use the cabinet speaker via the JAMMA
connector or by-pass the J-PAC and wire directly to one or two speakers in the
cabinet.
OR: Use a set of mains powered PC speakers. Either remove the
speakers from their cases and mount in the cabinet or simply place inside the
cabinet. This will give the advantage of power stereo sound.
But my JAMMA cabinet DOES have a power supply.
Most
cabinet power supplies will not function unless a game board is connected,
owing to insufficient load. It is best to remove the power supply completely as
the J-PAC does not need any power. All power comes from the keyboard or USB
interface. The monitor power must be left as it is though. DO NOT remove the
monitor isolating transformer if one is fitted.
What about cabinet safety issues?
Definitely a good
question! There are serious safety issues with cabinets containing monitors,
especially older types. I have covered some issues in the J-PAC installation
instructions. It is essential to check grounding thoroughly.
Do I have to have a JAMMA-wired cabinet to use
J-PAC?
Not necessarily. You could solder a JAMMA edge connector onto
your control harness and plug onto the J-PAC. This might be a way to implement
removeable control panels. But the I-PAC might be best for a non-JAMMA set-up
as it has screw connectors for the wiring.
I think my cabinet is a "JAMMA-PLUS" cabinet. What about
this?
JAMMA-PLUS is a fairly loosely-defined standard. It has a main
JAMMA connector and also an additional connector for buttons 4-6 for each
player. Yes you can use a J-PAC with this. The main connector plugs in the
normal way, and the wires from the extra connector can be connected into the
screw connectors.
Is there anything else I need to know before
ordering?
It's important to understand the implications of using an
arcade monitor on a PC before connecting up. The J-PAC is not a scan converter.
For best picture quality the J-PAC does not convert the scan rate, you need to
correctly configure the PC for 15Khz (if you have a 15Khz monitor), just as if
you used a passive cable. Not all video cards support 15Khz mode. ATI Rage Pro
and later ATI cards do and these are a good choice. Earlier ATI cards do not.
Many people use Advanced MAME for arcade monitors because it allows fine tuning
of the picture size etc for each resolution. This is a DOS version.
Some VGA
cards can work in Windows at 15Khz. Don't expect a great Windows desktop on an
arcade monitor though because they can only display 240 lines and so a 640X480
screen must be interlaced which results in some 30Hz flicker on horizontal
lines. This will not affect games, as these were designed to run on this type
of monitor.
Making the effort to get the configuration right will reward you
with an arcade-perfect picture which is difficult to achieve with an expensive
scan converter.
