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JPAC Video Issue

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  • JPAC Video Issue

    Hello Everyone

    My MAME cab has always been very hard to look at, the image is really unstable and has a sort of horizontal gitter to it. I always thought my chassis just needed a service but then I connected an MVS with Metal Slug X and the picture is really stable. I'm using a HD5450 with CRT Emudriver installed and a JPAC into the Astrocity cab.
    I've made a comparison video, the focus is a bit dodgy but you can see what I'm talking about.
    Would love to know how to fix this if anyone has any ideas.

    Cheers, Ben

  • #2
    Is this running through groovymame?

    If so, I'd suggest posting on this forum too,52.0.html


    • #3
      Cheers for the suggestion [MENTION=3942]mR_CaESaR[/MENTION]
      I'll head over there and post now.


      • #4
        Groovymame is awesome but it can be a very complicated beast to get set up right, I'm running the same set up as you and my Astro's look great, I'm far from an expert but I would guess that you might have some shielding issues from the video output cable from your PC maybe?

        I bought a shielded cable and it was a great improvement for one of my cabs.
        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


        • #5
          I had considered that, I'm only using the flimsy little VGA cable that was provided with the JPAC. I have gone to replace it once before only to realise it's a male-female cable and I've been too cheap to buy a good one to test with. And just now, while I am typing this post the solution came to me.
          Click image for larger version

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          Sent from my Nexus 9 using Aussie Arcade mobile app
          Last edited by Rustler77; 16th April 2019, 03:25 PM.


          • #6
            Didn't make any difference unfortunately, so I guess I can eliminate poorly shielded VGA cable as the cause.

            Sent from my Nokia 6.1 using Aussie Arcade mobile app


            • #7
              Do you have that motherboard mounted in the cab without a case? Perhaps the PC is picking up interference from within the cab or power supply? Can you run the PC outside the cab and plug it into a different power point to the cab?
              I leave my PCs in cases behind my cabs for easy access.
              Not as pro but you don't see them while playing.

              Sent from my SM-G920I using Aussie Arcade mobile app
              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


              • #8
                Hey Rat

                Its been setup externally and on a different power supply while I've been trouble shooting and its made no difference.

                I started this post on ArcadeControls and someone there is suggesting that I adjust the sync pot on the chassis. I didn't realize that was some thing that needs to be done when swapping out PCB's. Its a bit of a mission to get to the back of my cab but I'll give it a go I guess?
                Last edited by Rustler77; 17th April 2019, 08:39 PM.


                • #9
                  I just run my cabs with PCs and don't swap out boards so I have no experience with sync issues when doing that, but it's easy enough to mark your pot and take a picture of it so you can return it if needed then carefully adjust and see if you can get it looking better. Sometimes these old pots can break when adjusting them, but I have adjusted pots in both my cabs and not broken one.

                  If that doesn't work then I suggest showing your video to Jomac as he will know what's going on and what to do about it.
                  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


                  • #10
                    For sure adjust the sync pot. Hopefully that will fix the problem.


                    • #11
                      What is the sync pot labeled as? I have an Nanao MS8-29FSG I think.


                      • #12
                        It was suggested to someone on a different forum with a similar sounding problem that the MAME PC needs to be grounded to the JAMMA harness. I'm in Australia so my Astrocity has been fitted with a 240-110V step-down transformer and my MAME PC gets power from the back of the cab before it hits the step-down.

                        Also, sometimes I get a decent tingle from the JAMMA harness or the ground shields of things connected to it. I might have a bit of an earth leak or something, not sure if this would have anything to do with my video problem?


                        • #13
                          This might be sound obvious but are you running an interlaced resolution?


                          • #14
                            I don't think so, I'm using Groovymame with the super resolution modes installed.


                            • #15
                              Had my electrician brother and his multimeter around over the weekend. He pointed out that the power supply in my Astrocity wasn't grounded at all and that there was a 75V voltage drift between the mains ground at the back of the cab and the Jamma harness ground. Shouldn't the AC100V in and the DC out to the JAMMA harness have a common ground to stop this voltage drift?


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