Dreamcast Internal VGA modification

If you like your games to look the best, as myself, you probably already know that VGA is the only true solution for the Dreamcast. VGA-boxes aren't rare at eBay, but the only VGA box to deliver 100% perfect signal, is the original one. Those can be rather expensive these days. Therefore, we want to add an internal VGA port, and attach it directly to the mainboard - it gives the same perfect signal, as the original box, it's much cheaper and most 3rd party VGA-boxes sucks, compared to this solution. Of course, this requires to rip your machine appart, and make cosmetic changes as well.

Most people are already aware of mmmonkey's guide, but his print-schematic seems to contain some errors. E.g. V and H sync have to go through the 150 ohm resistors, as the first thing from the Dreamcast board, and they don't on his print.

Anyway, here's what I've made. I started drawing a schematic myself, which is 100% correct.




The best thing would probably be starting with the board. As the image above says, you'd need these components:

2 x Diodes
2 x 4700 ohm resistor
2 x 150 ohm resistor
3 x 220uF capacitors

My result:



The next thing I did, was to solder the first bunch of wires, to the VGA pins, as shown on my drawing. The last thing I did, was to solder the last bunch of wires directly on the back of the Dreamcast motherboard. Ain't no big deal really, but to make it all fit, was more of a challenge. I might have used to big wires for this.



Anyway - I solved the problem, by only keeping the switch on the back of the case. Next, I placed the VGA and Minijack -sockets in the old modem (I never used it anyway)






The results *trada*



Any problems or questions, please feel free to ask ;-)

 

so this forces true non-interlaced RGBHV for ALL games, not just the ones supporting the VGA box?

 

As far I remember, not all "non-VGA" games can be forced, but some :dance:
Anyway, with this, it's also possible to have both VGA and RGB -cables connected at same time.

 

The H and V and C sync are all active at once. I build my own C sync out of H and V sync... I have the internal VGA box mod done to my DC so that if I have my RGB cable connected, it uses regular RGB mode, if VGA is connected then it goes into non interlaced RGB mode.. otherwise it will be in composhit/s-vid mode.

 

looks great. I wonder why the regular cables are so hard to find.

 

I like this mod, it makes my Dreamcast actualy worth putting on a Monitor Switchbox.

Sweet. and Looks great!

 

Debating doing this mod. Do you know anything about adjusting the laser current so that I can read CDRs more easily? One of my PAL units struggles sometimes... I only have one VGA box - and I would like to use that in the lounge.

One question though... could you detail the sound mod a little more?

I'll head off to Maplin on the way home from work if I can get some good answers. I suck at electronics - could you list everything I need... i.e. what are the 'diodes'?

 

whoo this is awesome.

 

I can't really help you on that one, sorry - maybe another forum member got the answer

There ain't much detail about the sound-part really - it's just a mini-jack socket, with three pins (L, R and ground) soldered directly to the outputs on the Dreamcast mainboard.

3 x 220uF capacitors
2 x 4700 ohms resistors
2 x 150 ohms resistors
2 x diodes
1 x 15 pin D-Sub she (VGA) socket
1 x Mini-jack socket
1 x Switch (6 pins - http://el-supply.dk/Shoppix/60162.JPG)

Circuit board (this type: http://el-supply.dk/Shoppix/7602.JPG)

Capacitors are radial-type.

I don't know the correct english name for those diodes I've used, but translated directly, it's "small-signal diodes - 100V - 0.2A".

 

That's great - thanks! I'll see what I can do. Would be great to have built in VGA.

 

The diodes are usually called '1N4148' diodes. This may also be a helpful guide to read:-
http://www.mmmonkey.co.uk/console/sega/dc-vga.htm
Hope the OP doesnt mind me linking to another guide

 

Thanks for sharing ! It looks damn interesting, maybe I'll try it soon

 

Nope, it's fine.

As long as people are aware of, that the circuit board on mmmonkeys page, isn't correct (as I wrote above). I've seen a couple of people, following his guide 100%, and they all had their Dreamcast fried

 

This is a cool mod! I think I'll try it on one of my Dreamcasts. I have one that gives no image via the multi out at the back so I think that could be the one to mod. I already have 1 Dreamcast set up with the official VGA box so it would be nice to compare the two, not that there's going to be any difference I guess.

yakumo

 

I ended up having to get different diodes because of stock issues. Will post back with results. They have a similar rating. I hope nothing breaks!

 

I found my shopping list just a minute ago, and as link83 wrote, it's the 1N4148 diodes I've used. Are you gonna try using two different diodes? If so, I can't guarantee for the results :shrug:

 

I am crap at mods... :noooo:

 

Yes - that happened to me too!
However, I emailed mmmonkey to let him know the error a couple of months ago and since then and he has updated the circuit board picture so it should be fine now. The component 'ordering' still isnt the same as that used on the original circuit diagram, but this shouldnt matter.
I have a circuit board picture somewhere that I corrected myself to match the original diagram exactly - if anybody is interested I will try and dig it out...

 

i have a third party vga box from ebay and the picture looks fine,but it works only with games that support the vga box.can you play ALL games through this vga mod?(even not in the best quality picture)i just don't want to swich between my pc monitor and the tv for the games that don't support vga.

as for mmmonkey i broke a saturn when i lifted the leg from the ic to do the 50-60 hertz mod,i accidentally pull the wire,and the leg was gone off the ic ..althought his guides are well detailed some things he say suck really bad.i was stupid trying that.on my other saturn i just cut the trace and connected it like all the other guides(even if you make a mistake it wont kill your saturn)

 

Cool, I might try this someday when I have nothing to do.:thumbsup: