Dreamcast Internal VGA Mod
The Dreamcast picture in VGA is stunning, the cost of VGA boxes is rising and falling all the time. It is quite easy to make your own VGA box or even add a VGA out socket onto your console. Only a small number of parts are needed so it’s quite cheap :)
This is basically 99% the same as the guide on DCEMU, I did alter it a bit as when I plugged in an RGB lead it also grounded Pin 6 on the DC motherboard which then enabled VGA mode again and caused my TV some problems! So instead of linking pins 6 and 7 and then grouding them, I kept them seperate and grounded them individually (still using a single switch – a double pole, double throw switch).
So here’s my slightly modified diagram, pin 7 labelled as RGB Select, and a different switch used.
I can’t find the original post now, but I’m sure that ptr.exe on DCEMU also posted a stripboard layout for the above diagram. I did scribble it down on a piece of paper, I reversed it so that I could hide it in the case a bit easier and leave room for a modchip. Here’s my slightly modified design.
Here’s a picture showing you the necessary solder points on the back of the DC motherboard (again, source from DCEMU, I’ve marked some extra Ground points you may want to use, you can also see I have added some solder to the pads to make soldering easier later on – oh, and I’ve soldered the audio wires also!) (second picture by Link83 :) cheers)
Finally, a picture showing all the components
First prepare the stripboard, 11 holes wide and 7 holes tall. Make some cuts/breaks as shown in the diagram above and the following photo.
It’s a very simple stripboard (great design by prt.exe), soldering up should be quick, here’s the diodes and resistors soldered on.
Followed by the capacitors and the underside of the board.
Next up I soldered the VGA socket, the following photo isn’t very clear – but I put some solder in the holes on the back of the pins, I also linked up the ground points using a cut off piece of resistor leg. After that it was just heat the solder up and put the wires in the holes.
Using the photos, diagrams and info above solder up the wires for the VGA signal, VGA switch and if needed Audio.
Here’s how I wired up my VGA switch
I *think* you could use the standard DC composite lead and get sound from that, BUT I decided to mount a 3.5mm audio socket on the back of my console. Here’s how the socket I bought needed to be soldered up
Here’s my motherboard soldered up, it took me a while to decide how to route the wires (more info on that in a moment)
I made this hole in the bottom metal shielding so that VGA wires can escape without getting squashed (I also insulated it so that they don’t snag on the edges). The Audio and Switch wires come up at the rear of the console by the modem connector.
Now it comes to mounting the sockets and switch, I forgot to take many photos of this bit, IF I was doing it again then I would have mounted them all a little bit higher, in this position the interfere with the metal base of the GD-ROM drive, I had to hack away at it to get it all to fit in. I glued the wires in place just to strengthen them.
Again, here’s the original guide that this is based on, I just altered it to suite my needs but you might find my page helpful too!
Just a few notes
On my Samsung LCD the image shifts to the left (or was it right?!) when the DC is in VGA mode, it doesn’t do this on my PC Monitor or on a mate Hanspree TV (I have since found out it does this with a VGA box too, so it’s the TV rather than this mod). I think it would be possible to do with without a switch by utilising the ground points on the VGA socket and linking them up to AV pins 6 and 7 (instead of linking the VGA ground pins together).
Summary of Components needed
- 1 x Double Pole, Double Throw switch
- 2 x 1N4148 Diodes
- 3 x 220uf Capacitors
- 2 x 4K7 ohm Resistors
- 2 x 150 (or 100) ohm Resistors
- 1 x female HD 15 socket
- 1 x 3.5mm audio socket/2 phono sockets (something for Audio!)
Hi! I was wondering about the “Switchless” modification. Is it just to solder the RGB and VGA cabel from the motherboard to the vga sockets ground? Having an hard time to find space to the switch and it would be easier with the “switchless” modd. Is there som risk to this?
Best regards Andreas
Hi Andreas
I never tried it, and it was a couple of years ago that I was going to experiment with it.
I think it would be safe to try it, I assume the outer casing of your VGA plug on your VGA cable is grounded (it should be), you could perhaps link up the outer casing of your VGA socket to pins 6 and 7, that way, when the VGA cable is plugged in, pins 6 and 7 are grounded which then enables the correct VGA mode.
Pete
It worked! If you start the console with an VGA cable you need to restart the dreamcast to use the ordinary socket :)
There are some games where doesn’t support VGA and if you want to play such of these games you need to flick the switch to disable.
Shall test it the next time im opening the dreamcast. its way to many loose cables in it right now, could hardly close it this time ^^
hi, i’m attempting this mod and am a little confused. i may sound like a total noob but theres a couple things i dont get.
Where youve linked the ground on the vga, i cant seem to make out, from the picture anyway, which points to link.
Also, where does the 5+ wire from the vga go board go? i cant figure it out surely vga doesnt have a 5+ volt input?
but yeah, i’m new to this and i appreciate if anyone could clear it up for me.
thanks
Hi
It’s probably easier to use the diagram, the points which are black dots on the VGA socket need to be linked together and then soldered to Ground.
Some volts do go over the VGA signal, again, the diagram shows that it gets linked up to the Horizontal and Vertical Sync via some resistors, which is shown on the image below of the board layout.
Hope that helps.
Pete
Hey, Pete.
I’m just curious that if I go the VGA route, do I need RGB also? I’m planning to do most of my consoles RGB out to a CGA/EGA/YUV to VGA scaler board like you have. Would it be necessary in this case for the Dreamcast?
You know off hand if the games that do not play in VGA mode plays fine in RGB mode?
Thanks!
I *think* that the games which don’t support VGA, do support RGB – I can’t remember where I saw that though!
There’s always patches and/or forcing games into VGA mode though I guess.
So, say I added the switch for VGA and RGB. Would the composite/s-video from the A/V out port still work? IF I wanted to use it on, say, a friend’s TV that only has composite on it, will I still be able to with this mod?
Hi,
I’m planning to make a smt version of this + scanline, and I have a few questions.
Is 1/8 W enought for the 4.7k ohm resistor? (I’m not sure)
Is 1/4 W enought for the 150 ohm resistor? (I think so)
Is 25V enought for the 220 uf capacitor? (I think so)
Shouldn’t there be a 0.1 uf ceramic capacitor in parallel with the 220 uf one?
Thank you!
Hi, i followed ur guide.. but I have a problem..
I connect the console to my samsung tv and i can see the image (at first clock setting.. yes, I have to change battery). but after that, the screen becames black and I read “signal not supported”. Instead if I use VGA box, everything works well.
Why does it happen? my tv problem or what? thx!
@earthsaker, Disconnect power from the console and the Tv, wait a 1 minute or 2 and try again issue should now solved
What is the effect of using 100ohms instead of the 150ohms?
Thanks very much for the guide :) just finished doing the mod. I soldered the perfboard in reverse as I assumed the pic was the back of the board because the cuts were shown but it still worked :P thanks again for the great guide.
Greetings,
Thanks for the great article and site.
I feel almost ashamed to ask this as i’m in the middle of an engineering degree, but i can’t test the DC as it’s still in the workshop. My question is essentially: what does the switch toggle?
Should the VGA work with both switch positions (because i read somewhere how it’s switching to 15kHz) – can i still use composite if the switch is in RGB mode?
Many thanks.
It is also possible to add s-video and rca video and port or maybe just use add vga, s-video and rca video and use a 3.5mm for audio to save space?
and if so is there a guide to do so?
When i boot up, i get a black screen and the dreamcast boot sound effect.
Both VGA and Composite.
Did i break something?
I found the pinout of the A/V connector and a schematic for a VGA box. Instead of building the circuit in an external box, I decided to build it inside the dreamcast. Any suggestions further?
Howdy!
Firstly, another great tutorial – very well described (I did your TG-16 region mod, which was equally as easy to follow for a newb).
Just wondering – what voltage should the caps be? 16v/24v?
Cheers!
Dave
I am thinking about doing this mod with my DC and I have a question for the people that have completed this mod successfully.
What was the wattage rating of resistors you used?
Great post, completed this with very little trouble. I also decided to go ahead without the switch so I also have the “switchless” version. The chasis of a VGA cable is connected to at least one of the ground pins it seems. I twisted the RGB and VGA wires (pins 6 and 7) around the screw on the inside of the case that holds the connector in place. When a VGA cable is plugged in, it grounds it and uses VGA mode, when the cable is unplugged, the pins aren’t grounded and it can be used with regular RGB mode. Thanks a lot for making this
Completed this mod a while ago. To sum up some stuff:
1/4W resistors are fine and what I used.
Off the top of my head, the caps I used were 16V, but in this case, I don’t think it may matter.
The DPDT switch allows it so you can switch from VGA/Composite to RGB (for use with 15Khz monitors ie. Sony PVM monitors). Probably unneeded for folks in the US. I installed it anyway since I’m gonna have a SCART cable made for my DC.
The 3.5 phono jack doesn’t need to be installed, but it’s convenient. Audio can be taken from the AV cables with no problem.
The space in the back of the case is REALLY TIGHT! Plan accordingly. If anything, and with some soldering skills, you can use the unused MODEM and install the VGA board, switch, VGA connector and 3.5 (and an RCA jack if you want composite out) inside the MODEM’s casing.
Pete: Thank you again for this great guide.
Hi I was wondering if anybody knows the max voltage for the capacitors used and the wattage of the resistors used as the person at my electronic store said this was important information I needed to be 100 percent sure I’m getting the right part but they did ended guessing and selling me some parts anyway but I think there may have been some miss communications as I think they sold me few wrong parts if anybody can tell me what they are it would be appreciated
3 x CAP ELECTROLYTIC 2200uf 16VDC 105 deg
2 x 4.7k ¼ watt Resistors
2 x 150ohm ½ watt Resistors
2 x 1N4148 Diodes
1 x on/on bat handle switch
You are the best!
Thanks for this guide :)
I had this mod done for me long before I started doing my own mods. The guy told me that after the mod was done all video would be at 31khz (So scart may not work even after the VGA mode was switched off)
Anyway since then I have looked around at this and 31khz is when pins 6 & 7 are grounded. So I’m guessing when you plug in a RGB scart cable that it grounds pin 7 and if it has been linked to 6 – then it remains at 31khz?
I am wondering if your DPDT switch method will leave the video mode at 15khz when the VGA mod is switched off?
Thanks
How would one connect sync for a Sony PVM in RGB mode? It has 4 connections, R, G, B, and sync.
Do I tie the Hsync and Vsync together into a single cable? Just use the Hsync?
Or run a separate line from the Dreamcast’s CSYNC line?
The diagram from DCEmu that this is based on seems to be derived from another schematic but with some of the sync circuitry simplified out. http://devcast.dcemulation.org/mods/internalvga/vga.php
It makes me wonder if anyone’s built from the schem on this page and successfully used it for 240p output for the handful of native 240p games like Bangai-O. No doubt it works fine for VGA which is the main thing people want.
I shall continue my research. Thanks for this, Matthew
What is the wattage of the resistors and what is the voltage on the capacitors?