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Space Invaders: Reset Line Mystery

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  • Space Invaders: Reset Line Mystery

    Hi all,

    I've just been testing a SI Power supply. The 12,5, and Neg 5 volt lines are good. On power up the reset line is going high ( 5 volts), and pulses (negative low) for a bout 5uSec. The frequency is about 8.3 hertz. Bit confused why this would be doing that

    I don't have a working SI cab at this point so I'm kind of in the dark when it comes to getting a SI board going. I know there's some difference between SI Delux and the Original, some sort of watch dog circuit was mentioned in a very short article I got off the net. Any one know what's going on here. I figure a cpu that's continually reset will not work, or is this part of the hardware's operation?

  • #2
    If it keeps pulsing then the watchdog curcuit is working either because the curcuit itself has a fault or the CPU has crashed for whatever reason.
    Even if you have tested the PSU it depends on how you tested it (multimeter vs scope) and where you measured it (at PSU at edge connector or at back of PCB furthest from edge connector)
    Caps may also play a role in PSU's and wont always make the power "bad" with a simple multimeter test.
    If all thats OK better crack out the skills and a probe at the very least....
    Always interested in Retro and Current gaming

    https://www.gamedude.com.au

    Comment


    • #3
      More on the topic of reset lines

      Thanks for your reply. Most pinout diagrams I have found on the net say you can ground the reset line, and after a bit of noise the game will start (Midway).

      I used a suggested circuit that made use of a small electrolytic, a resistor and a 7404 driver(inverter), to emulate the reset. Starts High when powered on, stays that way for a second, then drops to GND level.

      The supply is in question is a Taito and I checked it with a scope and multimeter. This supply was said to be for Taito SI tabletop and crazy climber. I think Taito PCB's have a pulsing reset line from the Power Supply, where as Midway doesn't. If anyone knows any different, please let me know.
      Last edited by taito; 21st January 2010, 12:01 AM.

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      • #4
        I have never heard of a CPU that needs a pulsing reset line to operate. It should be high unless theres a fault.

        Edit: Or low, in this unusual case.
        Last edited by Hewitson; 21st January 2010, 08:28 PM.

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        • #5
          If you want to move away from the Taito supply for bench testing, you can just use a switch mode supply and tie the re-set low.

          Regards,

          Johns-Arcade.

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          • #6
            Unless you want to keep the linear psu for originality purposes I'd be doing what John suggested and installing a reliable switcher.

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            • #7
              Thanks for all the replies guys. Yeah, I've been using a switching power supply for bench testing and I recently purchased the Taito PS a while back and if it's not broken, I think it does have a pulsing reset line, but it's not directly connected to the reset line on the CPU, goes via counter territory etc and other stuff. Forcast: Common sense should prevail shortly.

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              • #8
                Six years on. Thought I'd tie up this thread.

                The Taito power supply was faulty.

                Used a switching power supply instead for testing and set the POR, (power on reset) line to zero, using a ground.

                End of.

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                • #9
                  Originally posted by taito View Post
                  Six years on. Thought I'd tie up this thread.

                  The Taito power supply was faulty.

                  Used a switching power supply instead for testing and set the POR, (power on reset) line to zero, using a ground.

                  End of.
                  Is the original a AAM60009?


                  Sent from my iPhone using Tapatalk

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                  • #10
                    Yes one of the original tabletop switching power supplies.

                    "Got to fix it one of these days"
                    - Ma and Pa Kettle

                    Ro

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                    • #11
                      Power supply schematic for future reference...





                      Namco Starblade - Taito Cocktail 14" x 3, 20" x 2 - NZ SI PtII Upright - Chase HQ DX, Taito Top Speed - Taito Grand Champion - Taito Safari - LAI SI Head to Head Cocktail - SI Cocktail Clone x 2, Pong Clone x 3

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                      • #12
                        Thanks Kaizen!

                        Thanks Kaizen!

                        That's great to have. I've always wondered about the little coin/credit PCB circuit.

                        And behold!

                        "Thoust has bestowed upon me the sight that makes no longer the mysterious ways of ye board that credits"

                        Much appreciated!

                        Ro

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                        • #13
                          This is just a follow up. The reset line starts low and goes high, a very short time after powering up the supply. And then it should stay there. A pulsing reset line is a symptom of a problem on the PCB. Hope this helps someone out there.

                          Comment


                          • #14
                            Originally posted by taito View Post
                            This is just a follow up. The reset line starts low and goes high, a very short time after powering up the supply. And then it should stay there. A pulsing reset line is a symptom of a problem on the PCB. Hope this helps someone out there.
                            Hmmm... thought it was the other way around.
                            Namco Starblade - Taito Cocktail 14" x 3, 20" x 2 - NZ SI PtII Upright - Chase HQ DX, Taito Top Speed - Taito Grand Champion - Taito Safari - LAI SI Head to Head Cocktail - SI Cocktail Clone x 2, Pong Clone x 3

                            Comment


                            • #15
                              Originally posted by Kaizen View Post
                              Hmmm... thought it was the other way around.
                              Hmmm, yeah you're right Kaizen,

                              I'd been spending a lot of time on the Spy Hunter, it's reset line is Active LOW.

                              So after a brief time the reset line on a Space Invaders should go LOW. I used a switcher, so I just hooked the reset line to GND, and that works fine.

                              On another front, I took that diagram you posted and fixed my supply. Thanks again for uploading that. It was a challenging repair, but the schematic made it possible.

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