The theory is simple – consider the following from Wikipedia’s entry on the SCART standard:

Pins 2 and 6 carry right and left audio respectively, and pin 4 can act as a ground. So, all you need to do is wire something off the SCART connector inside the transcoder’s box to add an output for your audio. The following should help you achieve such a feat.

Equipment needed:

• Two insulated wires of a length suitable for mounting the connectors – I used some old stereo RCA cables I butcher for various mods, as the shielding can be used to carry the ground to the RCA sockets
• 2x RCA sockets (red and black in this example) you can solder to with the screw-in sleeves to protect the solder points
• Solder, soldering iron, screw driver and drill/drill bits for threading the wires

Disclaimer

You mod your machine at your own risk. Myself nor anyone else is responsible for YOU modding YOUR RGB transcoder. If your machine doesn’t work as a result of this, don’t blame me – you do this mod at your own risk.

Step one:

Remove the screws so this:

Becomes this:

… and the part we’ll be working on is the SCART connector:

Step two:

Before we get started on the soldering, it’s time to mod the case. Since I wanted the wires to hang outside the case (there’s not enough room to mount two extra RCA sockets, though the NFG crew used a 3.5mm stereo headphone socket so that’s an option if you want to try something different), I drilled a hole on the output side of the case with enough give for two wires to hang out, and the whole is open at the top so I don’t have to thread anything through, the two wires simply sit in the groove and the top of the case will cover the top:

Step three:

Next up I cut the wires to length, stripped the ends, gathered the shielding and separated it from the signal and tinned all the tips. To make it easier at the SCART connector, I combined the shielding from both wires and tinned them together. This will make it easier to make one connection to pin 4 on the connector.

At the other end, slide the sleeves down the wires and wire up the RCA connectors. The inner portion of the shielded cable (in my case, one had red insulation, the other white) goes to the middle solder connection on the RCA socket, and the shielding goes to the outside connection. Solder everything up, test with a multimeter to ensure everything’s clean (optional, but recommended), then slide up and screw on the protective plastic sleeve.

Finally, tie a knot in the middle-ish of the cable – the idea is that the knot will hit the side of the casing before the wires tug on the soldered connections on the SCART socket if pulled, so experiment to find the best spot to tie the knot. An alternative method would be to use a cable-tie instead of a knot.

Step four:

Time to solder the sucker! Using the SCART diagram, locate pins 2, 4 and 6. In my case, they were on the top row and took the first three pins from the left with the connector pins facing me. Solder Right (red) to pin 2, shielding/ground to pin 4 and Left (white or black) to pin 6. Ensure your connections are strong and clean, we don’t want any dry solder joints! Again, a multimeter makes these kind of checks simple, so I recommend you use one to test everything.

Step five:

Finally, place your wire in the area you’re ground/drilled out of the case (if your hole isn’t open on top like mine, make sure you put the wires through the hole first before soldering in the previous step), plonk on the top of the case and re-assemble everything.

And there you go – external audio-out connections to ensure you can still get sound coming from the transcoder’s box

Related posts:

1. Getting component video out of a Sega Mega Drive (works for other RGB signals as well!)
2. Overhauling the Sega Astro City – Part 6, audio update
3. Overhauling the Sega Astro City – Part 2, audio amplification and fans

It’s a cheap mini stereo amp. In fact, it’s so compact, it’ll fit nicely inside the flip-up control panel on the Astro, so it’ll be easy to operate.

I wasn’t sold on these mini amps, but after reading some recommendations from other people who have used this same model on Aussie Arcade, I thought I’d give it a whirl. Considering the cost ($15!), I’m pretty happy with the outcome. Should work well to amplify both the mono amped output from the JAMMA harness, or the stereo line-out that needs amplifying.

As noted before, posts on the refurb are being done ad-hoc, so to keep track of the whole project, just use the Sega Astro City Overhaul tag, as the whole series will be added to it over time.

Related posts:

1. Overhauling the Sega Astro City – Part 2, audio amplification and fans
2. Overhauling the Sega Astro City – Part 5, roundup
3. Overhauling the Sega Astro City – Part 8, building a control box

In line with the previous post, I want to add a way to have a stereo amp in the cabinet to take care of line-level sources and enhanced stereo sound (e.g. Naomi, CPS-II, Sega Model 3, etc). So, in the spirit of making the cab as universal as possible, I need to look at adding in a small amp that can be switched on or off as required, and be able to direct either amplified sound off the JAMMA cable or amplified stereo output as required. So, this is what I’ve come up with:

It’s not all the difficult – I’ll need to rewire the 4-pin connector that goes from the speakers at the top of the cab so that they’re separated into stereo channels, then create a little switch to roll between a split dual-mono amplified output (from the JAMMA harness) or stereo output from the stereo amp, which in turn is powered off a 12v source (with switch to control when it’s on) and grabs its input directly from the PCB (Naomi, Model 2, etc).

This then means the audio can be setup in the cab when inserting a new board. All I’ll need are a pair of stereo RCA cables to run form the CPS-II or Naomi boards (and make a stereo RCA adapter for the Model 2/Model 3 boards) and run them off a pair of 12v mono amps I already have around the place, and I should be good to go.

The other addition I’d like to add is a stereo controller I can mount on the cab to adjust the output before it goes to the speakers as required – there’s currently a cheap knob the previous op added to give this kind of functionality, but it’s not a true stereo actuator, and doesn’t do much except distort the audio

Of course, the great thing with this setup is that it won’t cost much at all to add this kind of functionality. To make it clean though, I’ll plonk the lot into a small project box and mount everything inside it. This way, I can use the same project box to run a 12v switch to selectively power the 12v fan I got with my Model 3 kit before. And to make sure I don’t mangle my hand again, I’ll also grab a pair of 120mm fan guards to avoid any more stupidity

Thus ends part 2 – part 3 will deal with the lovely scope creep and deciding what to do with my monitor

To keep track of the whole project, just use the Sega Astro City Overhaul tag – the whole series will be added to it over time.

Related posts:

1. Overhauling the Sega Astro City – Part 6, audio update
2. Overhauling the Sega Astro City – Part 1, power supplies
3. Overhauling the Sega Astro City – Part 5, roundup