Pacogun (prototype)

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    • Pacogun (prototype)

      Hi! I'd like to show this awesome device... its' called Machine Gun Pacogun. I want it to be a simple, safe and cost-effective way to connect JAMMA boards to SCART TVs and audio amplifiers or speakers, with a focus on audio and video quality, reliability and electrical correctness.

      This a hobbyist project and a work in progress.

      Latest version

      The current version has with new features like brightness control knob, components placement and plexi covers inspired by the HAS and shares some components and pinouts with the Minigun. I got the idea of using an isolation transformer from the PARSEC:





      Features

      • R,G,B and Sync buffered and 75 ohm impedance matched using the famous THS7374
      • Individual pots to adjust R,G,B to achieve perfect color balance in any TV set
      • Pot to adjust Sync voltage level for picky boards / TV sets with tests points for easier adjustment
      • +5V and GND footprint
      • SPK+, GND and SPK- footprint for direct speakers with MVS Stereo or Konami Stereo games
      • Switch to select Line Level audio or direct speaker output
      • Molex Mini Fit PSU connector with the same pinout than Minigun
      • 2x DB15 connectors following Undamned pinout
      • Extended JAMMA Buttons 4 & 5 support via switch (thanks to plasia)
      • Buttons 4, 5 and 6 through JST Kick harness
      • Mini DIN-8 AV connector with the same pinout as Minigun / HAS / XRGB Mini
      • Audio atenuation featuring galvanic isolation with high-pass filter using polypropylene capacitors
      • 3.5mm Mini jack audio output that disables audio through Mini DIN 8 when used
      • AUX connector with DC coupled R,G,B, raw CSYNC, attenuated audio, +5V and GND
      • Three CSYNC modes: Buffered, Raw and through AUX connector
      • Discreet looking with no leds
      • Plexi covers for comfortable and safe use
      Extras
      • CPS1 Kick harness with JST connectors. Same pinout as Minigun and HAS
      • ~9-10 inches long PSU cable featuring Alpha Wire's 16AWG for low voltage drop
      • Minidin8 to SCART cable with XRGB Mini pinout

      The post was edited 37 times, last by rsignal ().

    • I like it.

      I particularly like how we are starting to establish a standard with superguns re power / controller / kick / video connectors.

      P.s. I'm going to announce yet another new supergun; the...

      Rocket Launcher Bazooka Nuclear Missile Cat Shooter Hyper Induced Mega Blaster Ring Stinging Sailor Butt Slut SUUUUUUPPPPPEEERGUUUUUNNN.

      Beat that. :D
    • Frank_fjs wrote:

      I particularly like how we are starting to establish a standard with superguns re power / controller / kick / video connectors
      I fully agree. The Mini Fit Jr is very nice! I use 16 AWG cable with this crimp tin:

      mouser.es/datasheet/2/276/0457…RIMP_TERMINALS-228628.pdf

      It's compatible with the same housing and receptacle.
    • This looks really nice.

      Regarding:
      • Galvanic isolation with high-pass filter using polypropylene capacitors and voltage divider for line level audio
      I'm curious about this circuit.
      I assume the transformer has two windings, and you use one per audio channel?

      How do you calculate the specs of the polypropylene capacitors to get the filter that you desire? Any pointers to how to do this?

      My existing knowledge of audio circuitry is basically none, but when I've been doing dumb superguns for myself, I've just copied this circuit:
      hacks.slashdirt.org/hw/supergun/
      where the thinking is stated as "Note: there’s no AC coupling (no capacitor on the signal path) because I didn’t think it was necessary: on the input side, JAMMA boards’ output should be clean enough. They’re driving a 8Ω speaker, any significant DC bias would destroy it, much more than such (reduced thanks to the higher load) bias would destroy the transformers. On the output side, measurements show that secondary DC bias is negligible, as expected. Also, 1/4W resistors are just fine. Given the load, they won’t see half that much power, and if something goes wrong, they’ll be nice little fuses."

      Do you get noticeable better audio with the caps?

      The post was edited 1 time, last by buffi ().

    • Level 1: MVS needs K4 on Jamma. (You are here)
      Level 2: Atomiswave needs K5 on Jamma. (Personally I like switchable up to this)
      Level 3: Chamma stuff needs k4-6 on Jamma. (Booo Chamma!)

      :) Looks nice. As Frank said, cool that we've got some real standards going. Now we can make a standard RGB->YPbPr converter, power adapters etc...!
    • @buffi my Supergun is Mono, so there's only one audio channel. However, I use SPK+ and SPK- terminals. They go to one side of the transformer and I get the sound from the other side, so the audio circuit of the arcade board is electrically isolated.

      I'm using a 1:1 transformer, the formula for the cutoff frequency is fc = 1 / (2 * PI * R * C). I place the voltage divider before the audio transformer. These links have all the information you need, check out the chapter "Subsonic protection" that explains the convenience of using a high pass filter:

      sound-au.com/articles/audio-xfmrs.htm
      electronics.stackexchange.com/…te-75w-speaker-to-line-in

      The Supergun sounds very nice, anyway I've only tested them with some cheap pc speakers and TV speakers so I've not made comparisons with different capacitors. I prefer to use the direct speaker connection when possible.

      Thanks for the suggestion @plasia , that's an interesting feature. I've not included it because I don't plan to have that hardware, but that option would make the Supergun more versatile, so I take note.

      The post was edited 7 times, last by rsignal ().

    • rsignal wrote:

      @buffi my Supergun is Mono, so there's only one audio channel. However, I use SPK+ and SPK- terminals. They go to one side of the transformer and I get the sound from the other side, so the audio circuit of the arcade board is electrically isolated.

      I'm using a 1:1 transformer, the formula for the cutoff frequency is fc = 1 / (2 * PI * R * C). I place the voltage divider before the audio transformer. These links have all the information you need, check out the chapter "Subsonic protection" that explains the convenience of using a high pass filter:

      sound-au.com/articles/audio-xfmrs.htm
      electronics.stackexchange.com/…te-75w-speaker-to-line-in

      The Supergun sounds fine, anyway I've only tested them with some cheap pc speakers and TV speakers so I've not made comparisons with different capacitors. I prefer to use the direct speaker connection when possible. Polypropylene caps are more reliable than electrolytics, that's a reason why I've chosen them.

      Thanks for the suggestion @plasia , that's an interesting feature. I've not included it because I don't plan to have that hardware, but that option would make the Supergun more useful, so I take note.
      Thanks for the pointers.
      The reason I'm asking is that I'm constructing a Jamma A/V splitter which has a pretty similar circuit (see bottom of schematic: i.imgur.com/8RFPc2n.png)
      It is also using a 1:1 transformer after a voltage divider from SPK+ and SPK-.

      I don't however use any caps whatsoever for my circuit (since the place I took that part from (hacks.slashdirt.org/hw/supergun/) didn't seem to think it was needed.

      Now I'm sortof curious, and think I'll try caps in the circuit and see if I can hear a difference. If not, then I can just bridge the connections I guess.

      Your supergun looks real nice. Basically a Minigun ADV beefed up with isolated mono audio. I like it!
    • Thanks! initially I planned to offer 5 of these boards as experimental prototypes to cover some costs but I'm waiting for a new revision and I want to do more testing, so I prefer to wait.


      I'm looking for an alternative DB15 part without screws from a reputable distributor. In order to avoid touching the metal case and the pins is to use a bottom and top case as the HAS does. Since these are the firsts prototypes, this will come later than sooner.

      The post was edited 2 times, last by rsignal ().