RGB 21 pin / SCART Lead to 15khz JAMMA Monitor

[tsenzen]

so this is what im trying to accomplish

i already have the jammaboard finger board, and was wondering if theres anything else missing?

ive read about the circuit to seperate the sync? but im not sure if i will need it for this particular setup?

any info will help, thanks.

[MonMotha]

Might need a video amp.  Arcade monitors usually expect signals around 3-5Vpp while most A/V and PC gear only outputs 0.7Vpp.

Depending on your console, you may also need coupling caps on the video lines to remove DC offset.  220uF is usually the standard, but you can get by with (sometimes much) lower when driving a high impedance input like an arcade monitor.  With SCART style outputs, the bias voltage is defined to be positive, so you can get by with polarized caps (+  side towards the console).  You can try without these caps, but if you get extremely bright video, you may need the coupling caps.

The sync separation you refer to likely has to do with the fact that SCART signals, and therefore most RGB outputs from consoles, usually use CVBS (composite video + blanking signal) for sync rather than TTL level dedicated sync.  A LM1881 (crossed by Intersil as the EL1881 which is often cheaper) will extract just the sync information from the CVBS line and output TTL level composite sync.  The circuit from the datasheet including component values can be used to satisfaction in almost all cases.

[tsenzen]

Thanks for the quick reply MonMotha

Where can i purchase an LM1881, or EL1881? are there diagrams for it? im a very visual person, and need clear diagrams to figure something out right away.. i also want to make the source (console+rgb21 cable) like a virtual 'PCB'. This is so i can move the rgb2jamma "pcb" around to all my different cabs whenever i need to...



with the information you provided me, I'm willing to try a dry run with what i have.. however i have a few other items in hand already, and was wondering if im able to achieve the same outcome with the provided components:

What i already have/own:

Also have

ive read about the LN1881 circuit to seperate the sync? but im not sure if i will need it for this particular setup? I believe i can just wire the SCART/J21 Cable directly to the J-PAC? since its doing all the amps already?

and one more thing im using:

If you can see the board that the wii cable is hooked up to:  im wondering if the monitor adapter that ultimarc makes is basically an LN1881? im also considering just trying to run straigh RGB from a console straight through this similar board?

So i've mentioned all the components, and am wondering what is the BEST option to get the initial image (diagram) ive made above working with the best possible performance?

any info will help, thanks.

(I have over 5+ cabinets to try it with, incase there are any complications due to specific monitor types.)

please help!

[Zebidee]

Monmontha certainly knows his stuff, but you could just feed the video through into the JPAC using a cut-off VGA cable, and plug that into any JAMMA cab. Or your could bypass the JAMMA altogether with your Wii cable & video-amp setup, but this will probably take more stuffing around on a cab-by-cab basis.

Using the fingerboard would be nice if yoiu could figure out some way to mount your video amp components on there too.

[tsenzen]

so i pretty much got everything working at this point,

all of my cabinets cept for the NEW ASTRO CITY's dont need the LM1881N chip.

im working on figuring out how to provide an amp to the connector to amplify the stereo leads. I have it working properly with the cabinets speakers and everything

heres the updated diagram:



some issues i have:

how do i make the stereo amp? so that i can amplifey the sound, than use the cabinet's master volume control to adjust the volume. Megadrive/NeoGeo work fine already, this is because they already provide a volume level on the sound.

why does the NEW ASTRO CITY's require an L1881 chip? where the OLD ASTRO CITY's work fine without one? If it does support NO L1881 Circuit, than what option do i change on the chassis so that its equivalent to its predecessor?

[Zebidee]

all of my cabinets cept for the NEW ASTRO CITY's dont need the LM1881N chip.

why does the NEW ASTRO CITY's require an L1881 chip? where the OLD ASTRO CITY's work fine without one? If it does support NO L1881 Circuit, than what option do i change on the chassis so that its equivalent to its predecessor?

I don't know, but for some wierd reason my own Astro Cab (Nanao 29" monitor, dual res) won't accept the latest ArcadeVGA card video inputs (thru JPAC). My monitor is fine, because it still works with my Powerstrip-15khz PC and arcade PCBs. However, there seems to be nothing wrong with the AVGA card because I have tested it with other monitors/SCART TVs and it is fine .... The first time this happenned I even sent the card back to Andy for a replacement as I assumed it was faulty. I guess it was faulty, except that Andy tested it as "working" which made life difficultv (However Andy still replaced it for me FOC, so full credit to him). I've tried other AVGA cards on the same monitor since, but with the same poor results.  Disappointing and confusing.

What is your monitor (& model preferably)? A Nanao, presumably? I just saw your diagram and can see that it is indeed a Nanao.

im working on figuring out how to provide an amp to the connector to amplify the stereo leads. I have it working properly with the cabinets speakers and everything

Check out these pages I did on basic volume pot wiring for arcade cabs:

http://scarvell.net/wiki/index.php?title=VOLUME_CONTROL_MOUNTING_AND_WIRING

Now that you have done it, do you amplify the RGB signals at all? I didn't see one in your most recent diagram.

[tsenzen]

Now that you have done it, do you amplify the RGB signals at all? I didn't see one in your most recent diagram.

I dont need to amp the video signals at all.. i just up the RGB gain by 30% and it looks perfect.

Ive noticed in your Volume control mounting diagram that it doesnt explain how i get the amplifier? or how that would wire in? unless the amp is actually the 'volume control' to begin with?

sorry to be noob here, but i need to just run my (Left -/+) & (Right -/+) with the same similar pot and amplification.. if i were to break open generic computer speakers will i be able to use the same components? This ideally is supposed to be wired in between the console and jamma fingerboard? or am i wrong?

[tsenzen]

ok, so i ripped open dell usb (5+) speakers

wired it into the connector and it works perfectly



There is a slight burning smell, not sure if this is just a symptom of the poorly made dell speaker pcb/amp or if im doing something wrong? i double checked all the connections to make sure there are no shorting... anyways it gets really hot, even for 5+. I had it on for about an hour and it seemed to stay the same temperature (not getting hotter)... still hot enough to melt plastic maybe..

I also went ahead and wired in an LM1881N chip to avoid all the monitor drama from my NEW ASTRO CITYs.

so now that this is done, im going to work on a housing..

i have a plan to wire out all th 1p/2p controller points and have it wire into a D-Sub25 connector.. im wondering, will everything fit on one of these 25 pin connectors, or do i need to split the load to 2 connectors? im thinking about actually making a seperate cps2 female adapter via wired controllers for the remaining buttons..  this will just make it easier when i move around many different cabs.

what are your thoughts?