Homebrew DreamCast RFU

If you're like me, chances are you don't have a whole lot of money laying around and spending actual green money on an RFU (RF unit) from Lik-Sang probably isn't something you're willing to do. So what happens when a Hungry Hacker such as myself decides he needs the Dreamcast hooked up to a TV without RCA inputs?

We hax0r our own RFU - that's what.

For this project I used our poor development Dreamcast Daisy, and an RFU from a Sony Handicam which has since gone on to greener pastures. The great thing about these RFU's as opposed to one for say, a DVD player is their size. The thing is smaller than a bite-sized Snickers, and thus lends itself well to hiding inside of the Dreamcast - which by any other measure is a rather tight space.

If you're attempting this yourself, check the voltages necessary to run the RFU you're using. Another great thing about the RFU I'm using is it runs on 3 to 5 volts, and it just so happens there's 3.3vdc available inside the Dreamcast.

You'll also need some sort of wire to tap off various things and run them to your RFU. In Daisy's case, we "shucked" the modem and used the inside of it's shell to hide the RFU, so we'll need five (if your RFU is decent and has seperate grounds for audio + video you'll need 6) pieces of copper wire about 10" long. I tore the wires off an LED bezel from an HP pavillion case which worked out perfectly.

The first thing to do is tear into your poor Dreamcast. Luckily, Daisy isn't a virgin in this respect and we've already done this for the take your Dreamcast apart article, which made things a lot easier. You'll want to carefully tear it all the way down to the mainboard, and take the mainboard out and have it in your hands.

Voltage Tap

Figure #1

Next, I had to find a suitable voltage tap for the RFU, which in this case turned out to be the 3.3 volt leg of the Power Supply board. If you are selecting a different RFU, bear in mind that you have three voltages available, 3.3v, 5v and 12v, all of which are clearly labelled on the legs of the PS board. They share a common ground, so you can basically take the negative off anywhere you want to but I decided to take if off the nearest ground pin.

I decided to tap the power from the bottom of the mainboard instead of directly off the Power Supply board, as this way I could later remove the Power Supply board if necessary. Simply flip your Dreamcast's mainboard up onto it's edge (you want the GD-rom connector at the bottom, facing away from you) so you're staring at the solder joints of the power legs, shown in figure 1.

In this case, I'm stealing power from the topmost leg(+3.3v) and the third topmost leg (common ground). If you wanted 5v you would tap the second and third pins, and if you wanted 12v you could tap the bottom two pins, with the bottommost pin being +12v. I decided to keep things sane and use the yellow and black wires for +3.3v and - respectively. I soldered the wires on while making sure I didn't join two of the pins together or short anything and I'm in business.

Tapping the A/V signals

Figure #2

Next, we must find where we can nick the signals from the RCA outputs. The easiest place to do this is from the A/V cable connector, although if you attempt this yourself you'll need a much finer iron than I used (I very nearly made a mess of this). Using an ohmmeter and the AV cable I quickly discerned the pins which correspond to the Video (Yellow) and the White audio cable - since the RFU I was using is only mono and most monophonic TV's in my experience request the white audio cable.

As you can see in figure 2, I have used 3 wires. I used black for ground, which is common for both audio and video on my RFU, and I used green for video and red for the audio. Assuming the connector is facing away from you, the fourth leftmost pin is Video out, the 3rd rightmost pin is Audio out, and the rightmost pin is ground.

So I simply soldered three wires corresponding to those pins and twisted them together. Now comes the fun part.

Routing the wires

Figure #3

If you try this yourself, routing the wires is something you'll have to take artistic license on. Personally, I ran the wires over to where the modem usually lives, running the A/V wires along the back of the Dreamcast, and the power supply wires around the Maple board, as shown in figure 3. What you'll probably need to do is run it up through one of the areas where the shield is bent around to allow it to be screwed down, as I have done:

I drilled two holes through into the modem's area in order for the wires to pass through. Next, I started to reassemble the Dreamcast, leaving the stripped ends of my wires hanging bare, and plugged it up to test it. I used a multimeter to check for the 3.3v on the yellow+black pair, and hooked a makeshift set of RCA cables up to my signal taps, and everything worked great.

Shucking your Modem

You may not want to do this, in fact you may even want your RFU to be external. But personally, this is not my software development Dreamcast, and I'm never going to use the modem on it. So I simply removed the modem, and removed the two screws that held it into it's white plastic case. Next, I went at it with a dremel, and removed the lugs that the screws go into, as well as some of the front wall to allow my 3.3v wires to come through unmolested. All in all, it took me about 10 minutes to hollow out my modem's case. When the project is finished, I'll have a 50ohm coaxial connector poking out of the back of the modem's cover, and I'll glue the modem cover on over the finished RFU.

Connecting the RFU

Figure #4

If you're doing this project yourself, your experience will probably vary greatly from mine. Basically, you'll need to determine which pins are which on your RFU, and wire it up accordingly. Unfortunately I decided prematurely to use the case from my RFU as a chewtoy, and the model number of it was left subsequently unlegible, or else I'd share it with you. But here's a pic of the RFU in all it's nasty glory:

Notice the temporary scotch-tape insulation? I will be hard-soldering the wires to the RFU eventually, as well as making an external Ch3/4 switch, but first Daisy has to live through a case-mod project before I can button her up for good.

If you get your Dreamcast online with an RFU, drop me a line as I'll be more than interested in hearing from you. Oh, if you kill your Dreamcast attempting this, you can email me, but chances are I won't care and I definitely won't buy you a new one. As always, your mileage may vary.

Hungry Hacker Industries