Fitting external audio jacks to a RGB to component transcoder

Posted Wednesday, 18th May 2011 under Hardware modifications
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If you have an RGB to component transcoder like the CSY-2100 (useful for playing RGB retro console on a TV without SCART or RGB inputs, but happens to have component video), you may have noticed the box doesn’t have any built-in way to get audio (stereo or mono) off the SCART adapter. However, it’s not too difficult to build this on yourself if your console has no other way of outputting audio by adding a couple of RCA sockets to your transcoder. Note that in no way do I take credit for the idea – that goes to legendary modding stalwart GameSX and their equally awesome NFG forums.

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 🙂

Overhauling the Sega Astro City – Part 8, building a control box

Posted Monday, 25th April 2011 under Arcade cabinets
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Today I’m going to talk about the control box I built as part of the Astro City overhaul.

The purpose of this was to achieve the following:

• Switch between stereo and mono output, with the mono input spliced internally to be two-channel mono audio, all via RCA sockets
• House a -5v output produced by a Negatron with a master switch to enable/disable the function
• Distribute +12v to a fan with a master switch to turn on/off the fan
• Distribute +12v to power the audio amplifier
• Route a GND connection to the JAMMA harness, which ensures GND runs across all connected GND loops on the harness regardless of which power connector is hooked up to the power supply (e.g. ensures GND on the JAMMA harness even if I’m powering a NAOMI board direct from the PSU)

The other aim was for the connections to be modular and terminated with molex connections. This way I could build the control box on the bench before fitting it into the Astro City.

The first step once I gathered all the components was to mark out the holes to drill for the RCA sockets and switches:

Once that was done, I drilled out all the holes and fitted all the sockets and switches.

Next up, I went about wiring the audio components together using a 3PDT (3 pole, double throw) switch to go between the two sources, and brought in a master voltage cable to bring GND, +5v and +12v from one of the extra connections on the Sun PSU that weren’t used for supplying the main voltage to the PCB or harness. From there, using hot glue and some cut-down wall plugs, I created some points to screw in some project board that acted as a voltage distributor and hooked up +12v to the two switches (one for the fan, one for the Negatron), and a second piece of project board to house the Negatron. I also wired in an extra GND point to be distributed to the JAMMA harness with the +5v from the Negatron, and added those along with a GND and the +12v for the fan to a standard 4-pin molex connection as used on disk drives in a PC.

In addition, I also wired a +12v and GND to a plug to fit the power socket for the audio amplifier.

The end result came out like this:

Inside view of the box:

Inside view of the top half:

Inside view of the base:

With this completed, I can start gutting the existing cab and modifying the JAMMA harness to suit the new setup and the various molex connections as part of the project.

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.