Ultimarc J-Pac Question - confused

[willmame]

Hi, I'm a little confused and could do with some advice...

I have a Jamma cabinet with arcade monitor that I am putting a PC into.  I had previously been told I would need a J-Pac adapter, and an ArcadeVGA video card.  However, I have just read that if you do not have an ArcadeVGA card, the J-Pac adapter will convert a 31kHz video signal into a 15kHz video signal to work on the arcade monitor.  If this is the case, do I need an ArcadeVGA card at all?  Are there any advantages to having one?

Thanks for your advice!

[CheffoJeffo]

First -- welcome to the boards!

Second -- Not really -- the J-PAC is not a scan converter. You may have heard about the half screen mode (see below), but that is different from what you want.

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.

http://www.ultimarc.com/jpac1.html

[willmame]

I'm still a little confused (I understand very little about video modes etc) but basically, if I was highest compatibility and ease of use (plus better quality) I should use J-Pac AND ArcadeVGA?

[CheffoJeffo]

Assuming that you have a Standard Res monitor (what game was in the cabinet before ?) , using a JPac and ArcadeVGA is how I would connect a PC.

At some point, you need to drive the video signal to 15khz for a Standard Res arcade monitor (VGA cards typically output at 31khz). The ArcadeVGA is an easy way to do that.

There are other options (other cards that can be forced to 15khz, software options, etc):

http://wiki.arcadecontrols.com/wiki/Arcade_Monitors

Without one of these solutions, the JPac on its' own won't give you what you want (nice single screen video on you arcade monitor), but it will protect your monitor (from being driven at the wrong frequency).

The JPac/ArcadeVGA combo is what I use to convert existing cabs -- they may be pricey, but, to my mind, well worth it.

[willmame]

Not sure what game was in it, I think I still have the board - I will look.

Thank you for your help, I think I will just buy the J-Pac and ArcadeVGA as it sounds easiest

Thanks!