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Thread: Problems with building my own supergun / jamma test rig

  1. #1
    . Cloud's Avatar
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    Sep 2018


    Problems with building my own supergun / jamma test rig

    Hello everyone,

    The last time I posted new thread someone told me that I should do some introduction to myself so there I go .


    My name Is Marcin, I'm from Poland I'm a retrogaming enthusiast like most of you I think . Currently I own over 60 consoles (many doubles) and a collection of over 850 games in total. It is hard for me to pick just one favorite system so I picked three - NeoGeo MVS (or arcade in general), Sega Genesis and NES.

    That much for the general info. Now about my background in arcade. I'm collecting arcade games for like 3 years now but I played MAME since I was 10 or so :P. Most of my collection consist of MVS cartridges although I have some arcade PCBs as well and an actual vintage arcade cabinet. I also have my raspberry pie set up to work with crt tv and recently I digged out my old pc to try out the groovy mame. Apart it is loud as hell it otherwise runs beautifully. Two years ago I consolized my first MVS system and since then I did two more and bough a supergun online from Retroelectronik (i hope I haven't misspelled the name). Since then I always wanted to take on the project to create one for myself and here is the reason why I'm starting this thread .

    I hope you guys will help me with the issue I came across. Please note that I do not have any electronic education whatsoever so I hope for your understanding. All I know is self thought through learning by doing. Oh and my English is lacking in some areas so please forgive me that too .


    Recently I've put together a supergun setup using ATX power supply from an old PC. I took care to pick a PS that supports -5V line. Firs I got rid of the all unnecessary cables and left only what is essential. I forgot that to start a PS I need to shorten the "PSU ON" with the ground so I need to add the momentary push button later on this project but for now a simple bridge with a cable will do.

    I wired everything as in this schematics:

    Then I connected the wires to the SCART socket like so:

    And... It does not work :/. I thought of some issues that may occur so also did this things:

    - I've checked if the PSU actually works on an old PC. It did.
    - I've checked weather the power cables after reattaching them together are at the same position as before de-soldering.
    - I've checked with continuity test if there are no broken wires.
    - I've checked the power switch for continuity when it is in its ON position.
    - I've checked whether the game boots on the other hardware.
    - I've populated the JAMMA cable with missing wires (except for key) just to be sure.
    - I've checked if the jamma edge connector and SCART are connected in a proper manner.
    - I've checked several different power cables and yes they work (PC turns on and the PSU in my supergun starts quietly buzzing when turned on).
    - The fuse on the PSU is intact. Also checked with continuity test.

    Then ting that I know I did wrong is when I put 22 Ohm resistors on RGB signals instead of 220 Ohm ones but I doubt I would change anything is case of simply working.

    I've ran out of ideas what cloud I did wrong here. Probably it is something simple. Something that I cannot see... So I need someones help on this. I will try to make some pics of the actual hardware although it is a tangled mess so don't hate me :P.

    Many thanks for any help! I would appreciate even smallest advises !

  2. #2
    Armored Scrum Object
    DasiyAge's Avatar
    Join Date
    Jun 2018
    United States

    What arcade boards are you testing with? I would check voltages at the jamma edge with your supergun plugged in and turned on. It's possible that a fuse is blown on the arcade board or that there is not enough amperage to drive all the components. Also what display are you hooking this supergun up to? Could be out of tolerance sync, but you should at least get audio that way. Also make sure you didn't mistake the 5v and -5v lines coming from the PSU

  3. #3
    I asked for a
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    Learned My Lesson.

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    Oct 2005

    Use a voltmeter to check the voltage coming out of the power supply. Check the voltage at the PCB edge, as well.

    Check the voltage on the SCART "trigger" pins.
    I turned off signatures. So should you.

  4. #4
    Akari's Big Brother
    awbacon's Avatar
    Join Date
    Jan 2009

    Quote Originally Posted by SpamYouToDeath View Post
    Use a voltmeter to check the voltage coming out of the power supply. Check the voltage at the PCB edge, as well.

    Check the voltage on the SCART "trigger" pins.
    Second this with additions; what PCB are you trying to make work? Google to make sure its not sensitive to variances in the 5V rail. Some boards don't seem to care if you are off at 4.98 or 5.02 but some boards are picky AF about their 5V line. It could be that it is WORKING, just not with the board you are testing it with.

    If you get all the proper voltages at the JAMMA edge, then yes check your video circuitry / cables...make sure its not WORKING but not getting an image.

    If you have one, or have access to a scope, you can check to see if you are getting a video signal on that. Granted it won't look like perfect NTSC signal, but you should still be able to see frames with color burst / sync signal before the frame.

    I'd really google the PCB you are using though. It could be as simple as THAT PARTICULAR GAME hates the power supply.

  5. #5
    Atro's Avatar
    Join Date
    Jan 2002
    Game Room.


    First of all, check if the TV you're using has RGB. Some TV's have SCART, but not all support RGB. Do you get any sound of it?

    And you don't need the +5v on pin 16. Just put a 560ohm resistor between pin 8 and 16. Then tie a +12v wire to pin 8 and you're good to go. That'll make you 4:3 ratio right away without the need to manually switch.

  6. #6
    . norton9478's Avatar
    Join Date
    Oct 2003
    Sombra Corporation

    Is it playing blind?

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