PARSEC Supergun Project

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    • PARSEC Supergun Project

      Here is my attempt at designing a Supergun PCB, I call it the PARSEC. While I have built a number of superguns in the past, they used off the shelf video converters and were mounted in enclosures. I've designed and built many circuit boards over the years, including a RGB - NTSC converter board and the Super 8 bit game console, so I figured why not try a supergun project.

      Testing and customer feedback so far has been great. Compatibility is looking pretty good. I'll post more pictures soon with different games.

      The PARSEC is powered by a standard ATX power supply for PCs (not included.) Since newer ATX power supplies do not provide -5v, the PARSEC has an on-board -5v regulator so the JAMMA connector has the necessary +5v, -5v, and +12v for arcade games. An arcade power supply can also be used (by modifying an ATX power extension cable.)

      PARSEC has a built-in NTSC video converter that provides composite and s-video as well as RGB output. A Sega Genesis 2 compatible A/V connector is used for RGB connection, and is compatible with all Genesis 2 A/V cables (even RF.) All outputs have 75 ohm drivers.

      Audio line out is provided through a 1/8" stereo headphone connector or the Genesis 2 A/V connector. Since the signal from an arcade game is intended for speakers, this signal is attenuated to an amplifier safe level. Audio isolation transformers protect your TV or receiver.

      Neo Geo compatible DB15 controller ports and kick harness connection header make the PARSEC compatible with 6 button games.
      A 6 pin connector is included to make your own kick harness (soldering required.)


      • JAMMA, JAMMA+ compatible
      • 24 pin ATX power input connector (also works with 20 pin ATX)
      • Push button on/off switch
      • On-board -5v regulator provides up to 1.5A
      • Power on/off switch for -5v regulator
      • LEDs indicating presence of +5v, -5v, +12v, and standby power
      • Built-in NTSC video converter
      • Genesis 2 compatible A/V connector for RGB video
      • Composite video and s-video jacks
      • 1/8" stereo line out jack or Genesis 2 A/V connector provides audio
      • Genesis 2 A/V audio output disabled when 1/8" audio is connected
      • Stereo / mono switch
      • Audio attenuation circuit with isolation transformers
      • Neo Geo compatible controller ports for players 1 and 2 with standard pinout
      • Credit, test, and service buttons on-board
      • Kick harness connector
      • Buttons 4 and 5 on JAMMA connector can be disabled with DIP switches
      • Basic button remapping option: credit and button 5 can be swapped by moving jumpers

      I've been offering these on and ebay.

      Price is $124.00 plus shipping.

      I am working on a HAT board with VGA connector for RGB which I hope to have available soon as well.

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    • The PARSEC has straight through power connections from ATX to JAMMA. A good ATX supply should keep consistent voltage regardless of current draw. There is no voltmeter built in, mostly due to lack of room. There are points on the pcb for measuring voltage or soldering wires to connect a voltmeter.

      I'm working on a arcade power supply adapter for the PARSEC also. I may offer a version that omits the -5v regulator to save money since this wouldn't be needed. The Texas Insturments PTN78000AAH regulator is $14 by itself.
    • Welcome! Good to have some superguns shipping stateside, yours look promising. Maybe some folks on here with audiences will want to review ‘em for you... And also I’d expect folks will want to know about how you’re dealing with two troublesome/variable topics when it comes to arcade boards - your rgb amp/decisions and how you’re dealing with sync (both hard-to-sync arcade boards like Taito F3, and sync as it relates to arcade vs consumer gear).
      cabs: sega blast city x2 | taito vewlix c + egret ii
      links: klov/vaps games list | custom fight sticks
      working on: dumping GALs and ostensibly repairing stuff
    • Nice project!
      Wondering what the mono/stereo switch does? Allow for MVS pinout or is there a stereo input header in so I can boards like Konami etc and run them in stereo via the Sega Genesis 2 cable?

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

    • It looks like RGB is amplified using discreet components and the S-Video/composite output is achieved using a BH7236

      The RGB may also be output through the BH7236 since it has that option and has 75R on each output line which means 3 less components required

      Sync is going through an LM1881 and then I assume via the BH7236

      Interested to see what low_budget says though :)
    • I have set aside a PARSEC review system to anyone who wants to try one out. I'm always looking for feedback and info on compatibility.

      I don't have any Taito F3 boards, so I honestly don't know how the PARSEC would do handling the video. I am also curious about OSSC compatibility.

      I use a XRGB mini framemeister to convert the RGB to HDMI. The Genesis 2 RGB cable needs 220uf capacitors and 75 ohm resistors inline the RGB lines to work correctly. I use a quality Genesis 2 SCART-J cable to the SCART adapter included with the XRGB.

      Here's the games in my collection and have been tested working

      Mortal Kombat 2
      Neo Geo MVS
      Bad Dudes
      Pit Fighter
      Street Fighter (the original)
      Double Dragon
      Killer Instinct 2
      Altered Beast
      Primal Rage

      For video I am using resistors to bring the RGB DC bias and voltage range down to acceptable levels. This is then input to the BH7236AF video encoder. For sync I am using a LM1881 with the composite sync output going to the BH7236AF. This chip has 75 ohm drivers on all the outputs, so I figured there was no need for any additional RGB buffer or amplifier.

      There are some sync options available with a HAT option I should have ready in a couple weeks. It will have a switch to select composite sync from the BH7236 or composite and vertical sync from the LM1881. This HAT will have 8p XRGB compatible mini DIN connector as well as a VGA connector.

      The PARSEC only supports stereo sound on compatible Neo Geo MVS boards. There currently is no option for output of auxiliary audio to the Genesis 2 A/V connector.

      Also, before anyone points this out, there are no RGB adjustment pots on the PARSEC. I didn't really have room to add them, and I like the "neutral" color balance the 1% tolerance resistors provide. Maybe I'm making excuses, but I didn't find any need to adjust color balance in the arcade games I own. There are solder points where these could be added if desired.

      I think I like this forum already. Somehow I like being bombarded with technical questions within 24 hours of first post, LOL.
    • The issue with using fixed resistors for the RGB lines is that the output varies between differing arcade boards. Most fall within a similar range but there are some that output a significantly higher or lower voltage than the 'average'. Sure, it may work fine with a small sample of 10 or 20 arcade boards, but factor in that there are probably 1000s of different arcade boards and you start to restrict your compatibility.

      Not a serious issue, most common mainstream arcade games will fall within range, but there will be some 'exotic' boards that present a problem.

      Not criticising your design, just pointing it out.

      Pots eliminate this issue and can be tuned with 100% precision which is why I like them. They also offer the handy feature of:
      • Being able to completly disable any particular colour channel. Helpful if one wishes to calibrate a monitor.
      • Compensating for a poorly calibrated monitor. E.g. you may need to drive red harder to obtain an even colour balance.
      Using a video buffer such as the THS range places the video circuitry of the arcade PCB under the load that it is expecting to be driven at and acts as a nice little fuse in a worst case scenario, preventing voltage overload being sent to the arcade board or the monitor. It also enables one to boost a lower than normal RGB output from an arcade board if need be, as well as lowering it to within spec by the use of a voltage divider at the inputs.

      Not a strict necessity but if you're going to the trouble of designing a supergun you may as well do it right.

      The LM1881 will add a slight delay and attenuate the sync signal by approximately 15%. Probably not something you'll notice with the naked eye onscreen but it will result in a slight image shift. Something else that can be alleviated via buffering all signals, RGBS, through a video buffer.

      I find the audio transformers an interesting approach but I would be concerned about them limiting the frequency response. I achieve the same result through non polarised caps and not DC grounding any of the speaker lines, thus protecting both the arcade board and any external amp, with wise ground plane management to eliminate interference. I'd like to experiment more with audio transformers though, if I can find one with satisfactory frequency response and cost.

      The BH7236 seems extremely similar to the Sony CXA2075 that I'm utilising. I'd be very interested to compare the differences seeing as they're pretty much pin to pin compatible.

      I'd love to try a prototype for the sake of comparison but really don't need any more superguns, so wouldn't want to deprive someone who is more in need. That said, if you want to send me one I'd be happy to test it out for a short time and forward it on to anyone of your choosing thereafter.

      P.S. Glad you enjoyed my DB15 pinout diagram! :)
    • thanks for the info. The forum here has done a good job of assembling a ton of smart technical people all in the support of the arcade hobby. Two other members use the forum to discuss their superguns ( @RGB’s HAS and @Frank_fjs’s Sentinel) and it’s a cooperative environment more than anything, exemplified by Franks post above. We just want good stuff for arcade hobbyists.

      I think it’s great to have a USA based option, as well as a low(er) budget option, in the market, and look forward to this and your future revisions (and other projects).
      cabs: sega blast city x2 | taito vewlix c + egret ii
      links: klov/vaps games list | custom fight sticks
      working on: dumping GALs and ostensibly repairing stuff
    • Thanks for the suggestions Frank_jfs

      I designed the PARSEC using a 2 layer PCB and I currently assemble them with a soldering iron.

      I really did consider using some sort of video amplifier and/or buffer, but decided on using resistors to place a load on the input signals & provide correct voltage levels to the BH7236 input. The RGB inputs are DC clamped at the sync timing from the LM1881. Those tiny pins of the THS7374 would be a bit challenging for me to solder. The smallest components I can hand solder are 0805 caps & resistors and SOIC ICs.

      I paid special attention to the audio and video grounding. The video ground is on the top ground plane in the center with all video circuitry grounded to it. This is joined to the main system ground at the Genesis 2 A/V output. The audio ground has a small switch that can connect it to the main system ground (necessary for Genesis 2 audio output) or leave it isolated for least interference.

      I'm using these 1:1 audio isolation transformers: Digikey part # 237-1121-ND They have a 200Hz - 15kHz frequency range. Some downsides of using the transformers is the cost and the amount of board space they take up.

      The BH7236AF is (almost) a drop in replacement for a CXA2075. I think it has better composite video output (when you add components for the luma trap.)

      In the future it's possible I could make a small PCB with 3 pots on it (for RGB level adjustment) that can solder on top of the PARSEC.

      While I am enthusiastic to loan out a review system, I may wait 1-2 weeks so I have the RGB video HAT ready as well. I think having the 2 different sync sources would be helpful for some arcade PCBs and the extra ports will make connection easier.
    • The biggest issue I had re composite video and the CXA2075 is dot crawl, but I'm using the internal trap. I did manage to abolish the dot crawl via the addition of an oscillator adjustment pot, which allows one to dial in a perfect image at the detriment of having to adjust the pot. Wish I could have found a way around it so that a pot wasn't necessary but on the plus side, once dialled in the composite output is stunning and I'm guessing most people would be utilising a better video signal anyhow.

      How is composite on the BH7236? Does it's performance vary pending on which arcade game you're running?
    • I would have loved to stay with a 2 layer PCB but the location of the controller ports made that impossible, the price you pay for ergonomics over circuit design. Utilising a 4 layer PCB has its advantages though, lots of room to space out video / audio / power traces, just damn costly to produce.

      My original board was a 2 layer board with controller ports either side. Quite liked that design but it's not what people wanted.

      I hand solder all my boards too, very time consuming. Not really worth paying assembly prices for what people are willing / expecting to pay for a supergun.

      Have you seen the Small Cab Supergun? It looks very nice, great implementation.

      Anyhow, good luck with it all, nice to finally see multiple options for quality superguns.
    • It's just my opinion, but I have used both the CXA2075 and BH7236AF in video converter circuits and I think the BH7236 is slightly better at composite video. I am using a fixed 3.57 mHz oscillator for the color subcarrier, so I am getting the dot crawl with composite. The adjustable oscillator is a neat fix, but incorporating something similar on the Parsec would have the issue of trying to fit more components on an already cramped board.

      The BH7236AF is nearly pin compatible with the CXA2075, so you could try it out without designing a new board. I believe the components connected to pin 17 are different, but that's about it.

      In order to fit everything on a 2 layer board it did require the components to be placed as close as possible to their JAMMA connections. I did manage to make it so no power, audio, video, or controller traces pass over each other (for the most part.)

      I have found that some games do need color, contrast, and brightness adjustment depending on how strong / weak the incoming RGB signal is. Having a RGB amp on the supergun would help correct the video on the boards with weaker signals and require less adjustment on the monitor. At the same time this would mean additional components in the video path, and small delay.

      The Parsec doesn't change the color, brightness, or contrast of the arcade PCB's JAMMA video output. I have not found any games where the video couldn't be dialed in using my TV settings. I decided to take a slightly different approach to the video conversion rather than make something very similar to what's already available. I'm not sure if it was the right choice at this time, but I am happy with my testing results.

      I attached screenshots of RGB to HDMI using the XRGB mini Framemeister (finally)

      (The screenshot of Mortal Kombat 2 was before I thought to adjust the color and contrast on my TV.)
      (Street fighter has one or more bad roms, so the background graphics are corrupted)
    • Thank you so much for the composite video details! I think I will try out the 7236.

      Those screenshots look great, no issues there.

      Is that an 8 pin DIN on the hat, to accommodate and celebrate the 8 DIN scart cables being produced by RGC? If so, great idea!

      I hear you re space / component / trace challenges. You did well to fit all that in a 2 layer board, kudos.
    • I no longer have any PARSEC v1.0 boards left so I did a redesign, the new v1.1 board.

      The v1.1 PARSEC Supergun has the following Improvements over the v1.0 PCB:

      • Thicker 1.5 oz copper layer
      • Wider +5v traces can handle loads up to 15A
      • 3 unused component footprints removed
      • controller ports now even with board edge
      • removed unsightly jumper wire to JAMMA connector (necessary on v1.0 because I forgot to connect video ground pin 14)
      • test and service button locations swapped
      • some improvements to component placement and footprint design
      • connection points on PCB for A/V modification possibilities (such as adding RGB adjustment pots)
      • it's purple now

      The v1.1 circuit is the same as v1.0 so no changes there.

      The HAT board I'm making will work on both versions of the PARSEC.

      It will take me a while to assemble small quantities of v1.1 PARSEC systems and additional HAT boards.
      I'll need to order parts and set aside quite a bit of time, so this will be a while.
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    • Thanks for the retrorgb post, SmokeMonster!

      I've found some other differences between the CXA2075 and the BH7236AF after comparing datasheets:
      • The BH7236AF has a composite sync output (pin 11)where the CXA2075 does not
      • The BH7236AF doesn't have an internal luma trap option like the CXA2075
      • Different components are used for the luma trap (connecting to pin 17)

      Assembly of the Parsec v1.1 is moving along. After building various PCBs by hand over the years I've developed a system:

      Since the SMT parts are usually much cheaper than through hole parts, I first order the SMT parts necessary to assemble all the Parsec PCBs I ordered. Then I will partially assemble a batch of around 10 PCBs using the SMT parts. When that is nearly done, I place the order for enough remaining parts to assemble 10 Parsec PCBs completely. This helps me avoid having an expensive parts order sitting around for a long time. After the "expensive" through hole component order arrives it doesn't take too long to finish assembly and make them available for order.

      I also made a power cable for those that prefer using a arcade power supply. I took an ATX power extension cable and popped out the pins I didn't need with a micro flathead screwdriver. Then I crimped on some forked wire terminals.

      I may have a version available with pre-wired power cable included and no -5v regulator installed.
      I could also offer partially assembled kits of the Parsec v1.1 but I haven't decided yet.
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      The post was edited 1 time, last by low_budget ().