Another CMVS (MV1C based)

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    • Another CMVS (MV1C based)

      This was finished, until I heard about DFO recently (and then after I heard about that, I found a pure digital HDMI mod that I'd love to try one day - maybe I'll buy another board to experiment on).

      But for now, here's my pride and joy, housed in a Hammond enclosure that's been used lots of times before by many people (including a red one I did last year but I made a few mistakes on). EDIT - model 1455T2201, I mount the end plates straight onto the the main enclosure - without the plastic bezels, for no reason other than I prefer the look.



      I decided to try and mount ports and sockets without any visible fastenings. I have some build photos, but it's pretty simple - the DB15 sockets are screwed into grooves that are on the inside of the case.

      I wish I hadn't cut the DB15 sockets central, I would prefer they were offset to the right, with the power button (with built in LED to the left), but I'm definitely not making another.



      Simple Stereo RGBS socket on the back (Deltron brand), with power socket and reset button.



      Cartridge connectors are secured to the underside of the case via brass spacers.



      Here's some of the innards (work in progress)
      Display Spoiler

      Thin plastic sheet cut to fit inside the cart slot.



      (You might spot the NeoBiosMasta with VMC installed in this photo, the UniBIOS is a licensed one which I programmed myself - hence a different label on it)


      Here's the brass standoffs, with fibre glass washers to protect the board.


      Power socket attached via screws to the inside of the case (black plastic sheet in place to protect PCB when I moved onto soldering the wires in place), and one DB15 secured.


      Side view, CR2 battery mounted in holder and secured to bottom of case


      Still to do:
      A lot of the techie stuff was taken from Xian Xi's guide :thumbsup:

      Cheers
      Pete

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

    • nam9 wrote:

      There is also @mikejmoffitts NeoVGA (if he is making more).
      Line doubled 480p output, or 240p digitally captured.
      I want to output both (switched) through a standard 8-pin DIN.
      Currently having issues with combining sync, but we'll see.
      If I make some more, I want to do a few simple PCB redesign steps to make it cheaper and smaller. If there is enough interest I could do a "one last time" batch. I have a few extra PCBs kicking around too.

      FWIW, the board also offers 480p and 240p YPbPr Component video.
    • is the amp really needed on the rgb lines?
      I just put 3x 75 Ohms in the RGB lines and picture is really good on my euro scart tv.
      What are the pros of using the amp?


      mikejmoffitt wrote:

      nam9 wrote:

      There is also @mikejmoffitts NeoVGA (if he is making more).
      Line doubled 480p output, or 240p digitally captured.
      I want to output both (switched) through a standard 8-pin DIN.
      Currently having issues with combining sync, but we'll see.
      If I make some more, I want to do a few simple PCB redesign steps to make it cheaper and smaller. If there is enough interest I could do a "one last time" batch. I have a few extra PCBs kicking around too.
      FWIW, the board also offers 480p and 240p YPbPr Component video.
      If you would decide NOT to make any more boards.. would you release the source byt any chance (wasnt this opensource in the start?) so that there is a chance to make a unit oneself?

      Thanks!
    • New

      citrus3000psi wrote:

      In regards to the HDMI I've ordered the dev board and have designed some breakout boards to test with. Not sure how good it will be. If its something that produces good results, I'll design a whole custom board to fit nicely. I have a MV1C, so it'd be designed around that.
      That sounds promising. I also found a thread over at neo-geo.com which linked to this untested board


      oshpark.com/shared_projects/QzfRYFGk
    • New

      @bytestorm I'm not an expert in this, but this is the answer as far as I understand it.

      Neo Geo Dev Wiki wrote:

      Video output (RGBS) from the JAMMA edge is high-level and non-uniform impedance. Very-high impedance, video-bandwidth amplifiers/buffers are necessary to prevent distortion and provide a steady impedance match for 75 ohm TV inputs. Wiring JAMMA video outputs directly to a SCART cable will produce a very dark (attenuated RGB voltage) picture. The picture will also have non-linear distortion because the video DAC cannot source enough current into the TV's load for most colors.

      ...

      The Neo Geo, amongst most arcade systems, outputs a malformed sync signal without proper serration or equalization pulses. This will not noticeably affect operation most TVs as the horizontal and vertical oscillator aberrations will typically fall within blanked video. Like video, JAMMA sync outputs are high-level and high-impedance. To drive a TV or broadcast monitor's sync input, the JAMMA signal should be buffered, attenuated and impedance-matched. Because the signal is bi-level, a biased logic gate buffer is sufficient. The attenuation/impedance match circuit should have a bandwidth >500 kHz to preserve sync's edges; a typical single-resistor solution forming a voltage divider with the 75 ohm terminator may not be acceptable.
    • New

      mmmonkey wrote:

      citrus3000psi wrote:

      In regards to the HDMI I've ordered the dev board and have designed some breakout boards to test with. Not sure how good it will be. If its something that produces good results, I'll design a whole custom board to fit nicely. I have a MV1C, so it'd be designed around that.
      That sounds promising. I also found a thread over at neo-geo.com which linked to this untested board

      oshpark.com/shared_projects/QzfRYFGk
      I've seen this board too, its a hat that goes on the Dev FPGA board.

      I also don't like using voltage dividers for the TTL level translation so I'm changing that up. I will be building the pcb design from scratch once I get a good test going.