Jamma Supergun I built works but 1 issue

ctozzi

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I built this Supergun to occasionally test my PCB collection and to show the working one's I trade or sell here, Anyways it works great however on my favorite series (Mortal Kombat ) all the games get stuck. The board goes through it's rom chip tests and after all show green they get stuck on that screen while the game plays in the background (I can hear it on the speakers). Every MK PCB does this, every other board, Killer Instinct, gauntlet legends, street fighter....and so on all test and play fine. I'm confused by this as all the MK PCB's are perfect, test &play perfectly in their respective dedicated cabinets. This all started when I removed the isolation transformer from this test rig figuring that an LCD doesn't need that. Take a look and see if I'm missing something here.
Thanks
Chris
 

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Probably the VGA to CGA converter pcb. IIRC, MK's sync signal was a little off from the normal and some converter pcbs wouldn't sync with them. I would try to adjust the settings on the converter or use the auto sync when you have an MK hooked up and see if you can get it to work.

Brian
 
I use that same video converter and I dont have issues with my MK boards (not saying that isnt the issue). Does your test rig have the pins connected for all the voltages including the negative ones? Maybe you have the +5 volts one one pin but need it on all the pins the way MK boards are setup? Just spitballing here...
 
maybe you need to change the video configuration on the adapter itself in its menu to something different.
 
Use the auto correct function for the converter.

there is no auto correct on the convertor. As soon as i re-hooked my 19" wells to the test rig without the convertor card the MK's all work perfect. Sucks because I wanted to use an LCD instead of the monitor to save bench space, which is very limited in my garage.
 
mk's output a strange video signal that cga>vga converters don't support (atleast none that i've seen).

feel free to correct me if i'm wrong but that's what i remember reading.
 
ya i figured that out through this process, I decided to go back to an actual arcade monitor. Just picked up a 5" one to try before i get a 13". thanks for all the help guys I'm going to custom build a control box to house this rat's nest of wires all over my bench.
 
You know we are all talking about your RGB to VGA converter, right?

I can see in the pic that there are 4 buttons, auto sync is the button in the south location of the 4.
 
Ya man, I missed them the first time when I had the same converter. Let us know what happens. I'm typing this as I watch your test rig video.
 
No good on the auto button, still the same issue, I'm going to go back to the arcade monitor it works perfectly like all the rest.
 
Here's my two cents. MK boards use a 53 hertz refresh rate. Most every other game is 60 hertz. I have heard of issues with these converters before and after getting a replacement, they are good. The converter doesn't know what to do with the 53 hertz because it's looking for 60 hertz and just craps out (freezes the image.)

I would vote for that being the issue. Sounds like these converters are hit and miss with who they end up working for.
 
Here's my two cents. MK boards use a 53 hertz refresh rate. Most every other game is 60 hertz. I have heard of issues with these converters before and after getting a replacement, they are good. The converter doesn't know what to do with the 53 hertz because it's looking for 60 hertz and just craps out (freezes the image.)

I would vote for that being the issue. Sounds like these converters are hit and miss with who they end up working for.

to add, I tried JROK's sync cleaner with his video encoder and it won't help the 53 Hz thing either. when I try to play them on my supergun through a TV the picture's shifted down a little bit, and of course, you have nothing to adjust it. lol
 
No good on the auto button, still the same issue, I'm going to go back to the arcade monitor it works perfectly like all the rest.

So no go on holding it for 5 seconds? Hmm. Might be like he said about the quality control. I used mine most on midway board like 2 on 2 Hockey, NBA Jam and MK1 and MK2.
 
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