Greetz and thanx go to those who made this possible - you know who you are!
Extra Radica Mods Tutorial
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We all know that a cartrige slot can be added to the Radica (thanks to @benheck), but there are other mods that can be done to improve this little marvel!
The picture below shows the locations of all these MODs on the underside of the Radica PCB...
Link to Full Size Images (you WILL need this!)
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http://www.box.net/shared/k2idfq3jif
Mod t€h 1st - Devsters SnK MOD
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1) Locate the HC174 chip on the underside of the Radica PCB (see picture at top of post)
2) Cut the trace as shown in the picture.
3) Solder pin 9 to the base of C31 (or any other +5v source)
4) Scrape the track in the location shown and solder a wire from here to cartrige slot pin B31.
5) Now play Sonic & Knuckles!
Mod t€h 2nd - 5v regulator MOD
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1) Locate U7 on the underside of the Radica PCB (the voltage regulator)
2) Desolder the three small pins and remove AS MUCH solder as possible from the ground pad at the back.
3) Heat the ground pad, and 'carefully' use an exacto knife to lift U7 off the PCB.
4) Get your new 7805 voltage regulator.
5) Solder the 7805 Ground to any ground point (see picture)
6) Solder the input to the middle solder pad (see picture)
7) Solder the output to the right solder pad (see picture)
8.) You now have +5v VCC on the Radica PCB!
Mod t€h Final - Stereo sound!
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(thanks to @Blackpata for his initial and invaluable research)
This is my version of the stereo sound MOD done by @Blackpata, just with more / better diagrams!
The diagram below shows the Radica Audio section, and what will need to be removed / replaced...
The Diagram below shows the MODDED Audio section afterward...
Now for the instructions...(not for noobz!)
---stage 1---
1) Locate the resistor R16 to the right of the LM358 chip - remove R16.
2) Locate the resistor R12 to the left of the LM 358 chip - remove R12.
---stage 2---
3) Solder a 2.25nF bead capacitor onto a 47k resistor in parallel to each other.
4) Solder these where R12 used to be.
---stage 3---
5) Cut the via between R26 and R25.
6) Solder a link from the top of R19 to where the top of R16 USED TO be.
---stage 4---
7) Solder a wire to where the bottom of R16 used to be.
8.) Connect this wire to the POSITIVE side of the 10uF electrolytic capacitor.
9) Connect the 13.8mH inductor to the NEGATIVE end of the electrolytic capacitor.
10) Connect the 668.4pF bead capacitor to the NEGATIVE end of the electrolytic capacitor.
11) Connect the other end of the 668.4pF capacitor to GROUND.
12) Connect the POSITIVE of LEFT audio to the other end of the inductor.
13) Connect the NEGATIVE of LEFT audio to GROUND.
14) RIGHT audio comes from the standard audio points on the Radica PCB.
15) You now have (reasonable) Stereo sound.
Q & A Section
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Q) Can I use other inductor values - 13.8mH is hard to find!
A) ANY inductor of 4Mh or more (up to 13.8mH) can be used...I used 6mH for example!
Q) Can I build ---stage 4--- on some veroboard for safety?
A) Yes, it's better to do this. (It's what I did)
Q) Can I use normal components if I don't have access to SMT components?
A) Yes, by all means - I did this, as they are easier to get than SMT ones...just harder to solder onto teeny solder pads!
Q) What do you mean by 'reasonable' Stereo sound?
A) Although the Radica DOES seem to emulate all of the Yamaha 2612 sounds quite effectively, some of these seem to have incorrect volume levels - so it will sound like some music notes / sound effecs are missing.
If you listen REALLY carefully, they ARE there - just whisper quiet! (best using headphones)
Although this could be due to the fact that some of the operators on the Emulated YM2612 are not entirely correct...
A more precise sound MOD would involve DOUBLE LM358 amps, and all four channels would be amplified separately - then fed into a stereo mixing chip like on the REAL SEGA Megadrive (Genesis)...I might have a crack at this sometime in the future...
Another idea is to use variable resistors for the four inputs and two outputs, this would let you do all the work with just the one LM358 - but adjust the audio so you can hear the quieter channels...
@Devster - if you decide to mirror this tutorial on your page, please give me and @Blackpata credit for our work...
Thanks!
