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JPAC - help me understand what it does for video signal?

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  • JPAC - help me understand what it does for video signal?

    Hi guys,

    Maybe its because its Friday and my brain hurts... but can someone please clarify what the JPAC does?

    I know it allows me to plug into a cabinet wired for Jamma (ie JPAC plugs into the harness).
    I know it functions like the ipac that it allows the controls to go through the keyboard encoder (so instead of a jamma PCB you're running a MAME PC for example)


    ... but what I'm not clear on is the video... does the JPAC actually act as a conversion from a regular VGA signal on a normal video card, in a PC running windows, to the CGA signal for the arcade monitor? Or do I still need an 'arcade vga' card aswell, or a VGA to CGA board?
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  • #2
    The jpac will not convert the signal, but will block the wrong signal.

    If you run soft15k, this will send 15khz from your video card to match the arcade monitor. Before soft15k kicks in (bios and windows startup screens) the video card will send the video signal using 31khz. the jpac can block the 31khz signal from getting to and harming your monitor. Once soft15k starts, the jpac with left the signal through.

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    • #3
      It also amplifies the voltage that the PC video card outputs from 1v to 4-5v - apparently 5v is a much better match for arcade monitors than 1v.

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

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      • #4
        So basically if you are wanting to run Mame on a PC in your cab, you will definitely want a JPAC, and 2 servostiks

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        • #5
          Jpac is for a jamma standard wired cab and adding a pc .

          Pc will need arcade VGA too.

          1 So you got pc with arcade VGA
          2 USB port and VGA plug into Jpac ,
          3 Jpac plugs into standard jamma bus ,

          Now you get a nice pc setup driving a cab without rewiring or cutting any joystick wires , monitor wires or button wires . Can still get rid of PC and plug jamma board back in as it was originally

          Note it will not switch seemlessly between all games

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          • #6
            Originally posted by Mikie View Post
            Jpac is for a jamma standard wired cab and adding a pc .

            Pc will need arcade VGA too.

            1 So you got pc with arcade VGA
            2 USB port and VGA plug into Jpac ,
            3 Jpac plugs into standard jamma bus ,

            Now you get a nice pc setup driving a cab without rewiring or cutting any joystick wires , monitor wires or button wires . Can still get rid of PC and plug jamma board back in as it was originally

            Note it will not switch seemlessly between all games
            I like the idea of leaving the lowboy that I'm fixing up at the moment as a proper jamma setup to run PCBs as required, but running a MAME setup for most of the time. I've heard of soft15khz before, but hadn't looked much into it.

            Can you elaborate on why I should go arcadeVGA over soft15khz, and what you mean by not switching seemlessly? I assume its because of different games wanting to run at different resolutions, in which case what is the user friendly workaround?

            Is a seperate VGA to CGA adapter the better option then (+ jpac for the controls into the harness)
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            • #7
              Yeah I really like it too and like to leave the original pcb in to show what it was

              The advantage of arcade VGA is it drives the monitor correctly from power on while soft15khz is a windows driver which supports specific video cards, so that is only going to display after windows loads the driver

              Not seemless as a mame player expects with a computer monitor. The original jamma cab has a specific monitor and chassis and is tuned for the original pcb

              So when you load different games it can require adjustment on the chassis . Sometimes this doesn't work and may need to instruct mame to run game at different size / freq this may not look / feel right for the specific game

              Also not expect to use setup for other than arcade gaming from this low rez era . I used vnc to remote over wireless to make pc changes

              Least frustrating setup it to select a series of games that require no monitor adjustment and that fully fill the screen and mame front end those ones per cab , then will get the most enjoyment out of this setup

              Gives that true retro feel , quite an effort expense with conditions, could put some x in 1 box instead
              Last edited by Mikie; 15th September 2012, 05:46 AM.

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              • #8
                If you like being able to configure mame settings then be careful buying a Chinese xxxin1. I hate mine, it's slightly better after dropping in a new hdd, but I still would prefer a PC in my cab. Having trouble with my jpac on 3 sided cocktail though, I suspect it's not standard jamma. Hoping to get some hands on advice with that at my meet

                Sent from my MB526 using Tapatalk 2
                Winter is here and I'm still riding more than gaming, my current goal = 100,000 meters elevation gain for the year - well ahead so far

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                • #9
                  Yeah I don't like the bootleg xin1s , some of the early ones are vbad

                  Let's say you want to run dk in a jamma cab with a pc , then Jpac and arcade VGA should give an excellent result. Then can add similar ones from the same era like Juno first and galaga and it will switch these with no problems

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                  • #10
                    Originally posted by Mikie View Post
                    The advantage of arcade VGA is it drives the monitor correctly from power on while soft15khz is a windows driver which supports specific video cards, so that is only going to display after windows loads the driver
                    If money is no object then get the AVGA, but if you prefer to spend the money on beers for when you are playing, then soft15k works fine.

                    Soft15k supports many video cards. The only real disadvantage is you get a black screen for the first 20-30 seconds until the driver kicks in. But there is an advantage with this too though. Original arcade machines don't show the bios screens, or windows load screens. Some take a while for the tubes to warm up. You are emulating the slow warm up.

                    I am a distributor for the AVGA but I think it is over priced. I would rather not make a sale than selling something overpriced.

                    But the AVGA is a great video card fi you still wish to go this way.

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                    • #11
                      what I've done is got an ati video card, and using windows x64, with the CRT_EmuDriver here: http://mame.3feetunder.com/windows-ati-crt-emudriver/
                      using groovymame, and everything is running great!
                      everything looks very authentic.

                      So as Danny said, if money isn't an issue then get the ArcadeVGA, otherwise i recommend one of the ati cards supported by the emudriver, or if you have Nvidia already, then use Soft15khz.
                      Either way, you'll be needing a JPAC.
                      even without using groovymame, you can try MameUIFX, which also gives a very good result on the arcade monitor.
                      Mine works seamlessly in that everything just works... yes, you get a strange looking screen on startup, but once the drivers kick in, everything is awesome!

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                      • #12
                        Careful with that strange looking screen at startup as it can damage your screen with the wrong frequency.

                        Jpac avoids this problem.

                        Does anyone know of any other circuits which will block the wrong signal?

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                        • #13
                          Originally posted by gameroom View Post
                          Careful with that strange looking screen at startup as it can damage your screen with the wrong frequency.

                          Jpac avoids this problem.

                          Does anyone know of any other circuits which will block the wrong signal?
                          yes, this is running through the Jpac.. i get 2 screens side by side, and the top half is a bit crooked... then once the drivers kick in, it switches to a res that the jpac allows through

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                          • #14
                            Thanks for all the info guys. I really like the idea of keeping my cabinet wired for Jamma now that I have a working CRT or two. However the issues with game/resolution switching is turning me off the idea because I don't want to make chassis adjustments for particular games.

                            I'm intending to run this setup in a lowboy with 3 buttons per player, so I'm ok to lose things like SF etc, but if it meant games like Wonderboy couldn't be played on the same cabinet as moon patrol... hmmm.

                            There are plenty of CGA>VGA converters around, is there an option of VGA>CGA or other alternatives that work around the limitations of using the arcade CRT? Although not as authentic, I guess I could put a PC Monitor in there and run a CGA to VGA converter between the Jamma harness and the monitor (for arcade PCB), and just hook up the PC directly to the monitor when in "MAME" mode?
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                            • #15
                              Originally posted by dmworking247 View Post
                              However the issues with game/resolution switching is turning me off the idea because I don't want to make chassis adjustments for particular games.

                              I'm intending to run this setup in a lowboy with 3 buttons per player, so I'm ok to lose things like SF etc, but if it meant games like Wonderboy couldn't be played on the same cabinet as moon patrol... hmmm.
                              Don't worry about that, you'll be fine with what you have. Especially if you get a compatible ati card!

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