MGDC for Dreamcast Jamma adapter

N80G80 · Nov 7, 2006

Hey guys wonder if anybody knows where I can get one of these for a reasonable price. Cosmico dosent have any more and say they are not going to get anymore. I was gonna post this in a want to buy thread (but it would be gone in like a day if i did) , but if someone could point me to a website or , have one themselves they want to get rid of for around $100.00 lemme know.

Thanks for any and all help!!

Oh and please dont link me to some DIY dreamcast jamma adapter. I dont have the time.

billd420 · Nov 7, 2006

Crap that sucks that cosmicco stopped stocking those... I guess I missed the train.

djjimmyjames · Nov 7, 2006

Buy a dc vga box, hack two madcatz dc controllers and buy a jamma waffer. Its really truly very,very,very easy. $30.00-$40.00 is your total cost. Should be a bit cheaper though.

billd420 · Nov 7, 2006

No its really not that easy... I followed those damn instructions to a T, and I can't get my 29" nanao monitors to synch to the signal. I dunno if its incompatible w/ my monitors, or if I fucked up (not very likely cuz i rewired the damn thing like 20 times over).

-B

djjimmyjames · Nov 8, 2006

billd420 said:
No its really not that easy...

-B

It was for me.

N80G80 · Nov 8, 2006

Yeah I said in the post I didnt want to DIY, I will ultimately do that if I have to. I just want to play some third strike (JP version) on my cab thats all and dont have an extra 500.00 laying around.

SpamYouToDeath · Nov 8, 2006

If you're having trouble syncing the monitors, try playing with pins 6 and 7 on the DC video out. They control display mode; both grounded for VGA, one but not the other (don't remember which ones) for 15khz, neither for TV.

But then again, I guess you don't even want help fixing your DIY one.

norton9478 · Nov 8, 2006

I couldn't get my electrohome to Sync unless:

I ran the Composite Sync through an LM1881 circuit...

Otherwise, the vert and horiz hold would be a messed up.

You may also need to amp up the RGB signal

Also, you might want to take the signal right off the RGB input, not the VGA output.....

Cut it right off of the pcb.

pixeljunkie · Nov 8, 2006

i would just keep an eye on ebay if you don't want to make one. I tried making one years ago, got frustrated and bought an MGCD. They pop up from time to time.

GrimDog · Nov 8, 2006

i heard the mgdc's were pieces of shit and were not at all plug and play, is this false?

N80G80 · Nov 9, 2006

no grimdog there not that bad from what I've seen. You do have to remove some grounds on the jamma harness to wire in the other 3 buttons but thats an easy swap

J69 · Nov 9, 2006

yeah im getting a blaze vga box to wire up my naomi to DC next week. One question though. WHATS A JAMMA WAFFER :lolz:

pixeljunkie · Nov 9, 2006

N80G80 said:
no grimdog there not that bad from what I've seen. You do have to remove some grounds on the jamma harness to wire in the other 3 buttons but thats an easy swap

yeah, what he said

GrimDog · Nov 9, 2006

does the mgdc allow you to use the cabinet control panel or do you have to use the dc controllers?

billd420 · Nov 9, 2006

I didn't give up hope yet on the DC -> jamma box... just been very busy with other projects.

@Norton: Do you have more info on the LM1881 circuit? I remember reading about it somewhere, using that circuit to sepperate the video synch from the composite line, but lost the link. Also, do you have a schematic for amplifying RGB signals? Finally, you mentioned taking the RGB right off of the PCB. Do you have pinouts anywhere for that?

This is as far as I got the dreamcast's video with my home-made kit:
http://www.big-bill.net/dreamcast.jpg

Now this is running on my 29" nanao monitor... the picture is pure sex when it is properly working (w/ PCB's).

I probably should open a tech thread, but i'm lazy LOL.

-Bill

pixeljunkie · Nov 9, 2006

damn, bill...very close! I could only get a white screen with sound. My controls worked though. I ran into probs because my VGA box apparently differed from all instructions I could find.

Yours is probably a pretty easy fix.

billd420 · Nov 9, 2006

pixeljunkie said:
damn, bill...very close! I could only get a white screen with sound. My controls worked though. I ran into probs because my VGA box apparently differed from all instructions I could find.

Yours is probably a pretty easy fix.

I'm hoping its an easy switch. I already snipped pin 7 on my blaze VGA box to enable 15hz mode, and it still doesn't wanna work. I even tried snipping pin 6 and reconnecting pin 7, but that didn't help either.

The instructions I read have you combine the vertical synch and the horizontal synch to become the video synch on the jamma connector. I'm thinking I need to build the composite separation synch to get a better synch signal, and it will work fine. Anyone have a nice diagram, and parts list for that circuit?

-Bill

J69 · Nov 9, 2006

jamma waffer anyone?

Im guessing a vga box will hook straight up to a naomi screen with it already being 31k?

How do you hook up thew cabinets sound though?

billd420 · Nov 9, 2006

J69 said:
jamma waffer anyone?

Im guessing a vga box will hook straight up to a naomi screen with it already being 31k?

How do you hook up thew cabinets sound though?

Jamma waffer is the same thing as a "Jamma Finger Board", google it for a picture.

If you have a true High-Rez arcade monitor, the VGA box should plug directly into it. Also, if you have a Naomi cabinet, you can run the stereo sound directly into the naomi's audio amp.

After doing some googling, I found a nice LM1881 circuit, as well as a company that will be sending me 5 sample chips. I have a Dreamcast Scart cable laying around, I'll probably ditch the VGA box approact, and utalize my Scart cable, since i'll be building the synch circuit anyways...

Wish me luck...

-Bill

norton9478 · Nov 9, 2006

billd420 said:
I'm hoping its an easy switch. I already snipped pin 7 on my blaze VGA box to enable 15hz mode, and it still doesn't wanna work. I even tried snipping pin 6 and reconnecting pin 7, but that didn't help either.

The instructions I read have you combine the vertical synch and the horizontal synch to become the video synch on the jamma connector. I'm thinking I need to build the composite separation synch to get a better synch signal, and it will work fine. Anyone have a nice diagram, and parts list for that circuit?

-Bill

Use the Csync, don't bother combining the HSync and VSyncs unless the C sync don't work.

make sure that you are getting the RGB signal before it gets to the RGB box... Don't take the signal off the VGA connector.

If you snip pins 6 or 7 (I can't remember which one it is), make sure the box is set to VGA mode.... This will ground the one that is not snipped...

billd420 · Nov 9, 2006

Yeah I decided screw the VGA box, its too much of a pain with my monitors... i'm positive my wiring is correct.

I'm going to go the SCART cable route. I have a few of the synch separating chips on order, so i guess time will tell if that solution works.

-Bill

norton9478 · Nov 9, 2006

billd420 said:
Yeah I decided screw the VGA box, its too much of a pain with my monitors... i'm positive my wiring is correct.

I'm going to go the SCART cable route. I have a few of the synch separating chips on order, so i guess time will tell if that solution works.

-Bill

You can completely disconnect the Blaze VGA box from the cable. I don't think that most SCART cables have a pin for CompSYnc....

billd420 · Nov 9, 2006

I need to double check my scart cable when i get home tonight that pin 20 is wired up. If it is wired, than pin 20 should be composite video. I've got everything coming in the mail to separate the synch from a composite line, so in theory i should be all set.

Oh yeah here's a good resource for the scart method of running Dreamcast on a jamma cab:

http://www.mameworld.net/pc2jamma/arc_dc4.html

-B

norton9478 · Nov 9, 2006

billd420 said:
I need to double check my scart cable when i get home tonight that pin 20 is wired up. If it is wired, than pin 20 should be composite video. I've got everything coming in the mail to separate the synch from a composite line, so in theory i should be all set.

Oh yeah here's a good resource for the scart method of running Dreamcast on a jamma cab:

http://www.mameworld.net/pc2jamma/arc_dc4.html

-B

My my old electrohome doesn't work when stripping the Compvideo signal...

ONly by stripping the Compsync signal.

I am looking at that pic... It looks like you just need to run the compsync through the LM1881.....

MGDC for Dreamcast Jamma adapter

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