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Thread: JPAC Video Issue

  1. #11
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    What is the sync pot labeled as? I have an Nanao MS8-29FSG I think.

  2. #12
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    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?

  3. #13
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    This might be sound obvious but are you running an interlaced resolution?

  4. #14
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    I don't think so, I'm using Groovymame with the super resolution modes installed.

  5. #15
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    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?

  6. #16
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    Long overdue update

    Shortly after my last post the picture on my Astro City started surging and eventually got to the point where it faded out to a black screen and didn't come back. So I sent the chassis off to @Jomac for a service. When it came back it was working about the same as it had been before it started surging, still had the high pitch squeal noise and it still had the jittery graphical issue that has haunted me for years. So I gave Jomac a call and he suggested the squealing noise might be caused by a failing step down transformer so I plugged in a spare one that I had for a US N64 console. Instantly all the noise coming from the cab disappeared and the graphics were perfect, everything I’d ever hoped for. The edges were stable and the whole image was rock solid. Happy as a pig in mud I went and had dinner with my family but when I came back 15 minutes later the picture had started surging again, so back to Jomac. While the chassis was away I replaced the temporary transformer with the brand new toroidal transformer. A few days later the chassis was back at no extra charge and the surging was fixed. I fitted the chassis to the tube, plugged everything in externally and tested with my MVS hardware. Now I'm presented with an entirely new graphical issue, the picture is still solid and sharp but I have a ripple effect rolling across the screen at a 45 degree angle. I soon figured out that grounding the jamma harness to the back of the cabinet fixes this new issue. The color is a bit washed out so I move on to adjusting the flyback, brightness and color pots and now the picture looks better than it ever has before. After playing Metal Slug 3 for about an hour I'm really happy with the results and power everything down and fit the tube and chassis back into the Astro City. I power everything up again only to find that I'm getting a new humming noise from the neck board that changes in time with the graphics and a graphical issue very similar but different to the original problem. Its at this point that I spit the goo, turn the machine off and not look at it for six weeks.
    Today before writing this post I thought I'd turn it on to see if it was behaving, it blew the main fuse and didn’t turn on.
    I think I can safely say my issues are not related to the jpac.

  7. #17
    Join Date
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    This cab has been much more trouble than it should for you.
    I hope you get to enjoy it working properly soon.

    Sent from my SM-A505YN 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. #18
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    Holy crap this cab has been a lot of trouble! My two lowboys need attention about once a year each when something goes wrong but your story is shocking :/

  9. #19
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    So I brought a fuses to replace the blown one about 6 week ago with the same rating (3A 250v) and since then its worked fine every power on with the exception of two times.

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