What's new
By:

Another CMVS (MV1C based)

mmmonkey

mmmonkey

Beginner
Joined
Aug 29, 2017
Messages
9
Reaction score
18
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)
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
 
Last edited:
Let me know about the HDMI mod. I heard it wasn't reliable so I could never use that for myself.
 
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.
 
nam9 said:
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.
Click to expand...
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 said:
nam9 said:
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.
Click to expand...
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.
Click to expand...
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!
 
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.
 
citrus3000psi said:
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.
Click to expand...
That sounds promising. I also found a thread over at neo-geo.com which linked to this untested board


https://oshpark.com/shared_projects/QzfRYFGk
 
bytestorm said:
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?
Click to expand...
TBH, I don't know, I haven't fully investigated it. I guess the amp buffers the Sync signal to so that they are properly in spec?
 
@bytestorm I'm not an expert in this, but this is the answer as far as I understand it.
Neo Geo Dev Wiki' said:
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.
Click to expand...
 
mmmonkey said:
citrus3000psi said:
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.
Click to expand...
That sounds promising. I also found a thread over at neo-geo.com which linked to this untested board

https://oshpark.com/shared_projects/QzfRYFGk
Click to expand...
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.
 
modology said:
the link to Hammond Enclosure is broken. How much did you buy the enclosure for?
Click to expand...
Glad you like it! I paid about 35 GBP for it, I forgot to include exactly which model of the 1455 series enclosure it was - it's the 1455T2201

Link is working for me? It's just a link to the manufacturers site. I think I just picked one up from ebay at the time.
 
Late to the thread, but what DIN-8 did you use, got a link to it? its much nicer looking than the ugly ones with the big flanges everyone usually uses.
 
Hi @finch, I just picked it up from eBay, but it’s a Deltron brand plug and socket - they have a locking mechanism - I haven’t tried a normal din plug in the socket - but it should work.

Ta
Pete
 
Still wondering about the PSG audio for the HDMI. I think it will necessitate a reimplementation of the AY-3-8910/YM2149 (PSG portion of OPN) or an ADC.
 
@mmmonkey Thanks for the reply, if It's Deltron it should be easy to source. I like how it looks, and I'm spending an inordinate amount of time right now sourcing the best looking parts for a new CMVS project.....I don't know why that matters so much to me, but it does, lol.

I'm pretty sure locking DIN's like are used for professional audio equipment is 100% compatible with non-locking stuff, minus the locking ability.

Love your CMVS btw, I made one using that same enclosure awhile ago, and seeing yours I really wish I knew to screw the ports into the ridges on the inside rather than drill through the enclosure. I tried to compensate by using nice polished dome headed hex bolts, but I think yours looks much cleaner.

Mine https://exitfromreality.imgur.com/all/ (WARNING! contains unrelated joystick pictures) I will note that I made this a long time ago, before the Biosmasta existed, hence the goofy bios install method. I've since replaced the motherboard in here and rewired everything to be cleaner and switched to the better Neobitz encoder so it has Component out in addition to S-Video.
 
You must log in or register to reply here.
Back
Top