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Sega Mega Drive Custom Switchless Region Mod PCB Install Guide

This installation guide covers installing the three Consoles Unleashed custom switchless region mod PCBs for Sega Mega Drive. The three mod kits are Switchless Region, Switchless Region + In-Game-Reset, and Switchless Region + In-Game-Reset + Dual Frequency Oscillator. This guide currently includes Mega Drive revisions NTSC-J VA1, PAL VA4 & PAL VA6. Any other board revision that has drastic variations to what is shown here will be added over time.

Mod Connections

Solder Maps

The custom region mod PCBs have labelled pads. If the solder map shows a solder point that is not labelled on the PCB, please ignore it. Only connect what is labelled on the PCB next to each PAD.

Language & Video / Power & Ground

The language and video rate setting on the mainboard are what determine the region of the Sega Mega Drive console. These jumper settings are easily overridden by cutting the connections and then supplying +5V or Grounding in varying ways.

  JP1-2 (Language) JP3-4 (Video Rate)
EN/50Hz (Europe) +5v Ground
JP/60Hz (Japan) Ground +5v
EN/60Hz (North America) +5v +5v

There are three different arrangements of jumpers in the Mega Drive. VA0 to VA4 which are horizontal and not sequential, then VA5 which is vertical and sequential from bottom to top, then there is VA6 which is vertical and sequential from top to bottom.

(IMAGE OF JUMPERS HERE) (IMAGE OF REGION SETTINGS HERE)

1 – First remove the capacitor that is connecting across the jumper if there is one.

2 – Cut the traces between the power/ground side and video/language side of the jumpers (red lines on images).

3 – Solder LAN and VID (before 5V and GND).

4 – Solder 5V and GND.

Mk1 Mega Drive VA4 (IC BD M5 PAL VA4)
Mk1 Mega Drive VA5/VA6 (IC BD M5 PAL)

Reset Button

For the PIC chip to control the regions of the Mega Drive it needs to take the signal from the reset button and then rout it accordingly. This is done by cutting the line going from the reset button and putting the PIC chip in this path. The PIC chip will then determine how the reset button is pressed and then send out any required signal. A quick press of the reset button will mean the PIC chip will send out a normal reset as if the reset button line was not cut. If the reset button is held, the PIC chip will send out signals to change the region and language and not send out a normal reset signal.

1 – Cut the reset button trace on the underside of the motherboard (red line on images).

Mk1 Mega Drive VA4 (IC BD M5 PAL VA4) Active low reset
Mk1 Mega Drive VA5/VA6 (IC BD M5 PAL) Active high reset

2 – Solder RB to the reset button pin.

3 – For RL, solder will need removing from the vias before soldering (blue circles in images). Scrape away the green solder mask from the small pad to reveal the copper underneath. Solder RL to this. For best results use the tip of a scalpel and view under magnification. The area should be shiny before soldering.

Mk1 Mega Drive VA4 (IC BD M5 PAL VA4)
Mk1 Mega Drive VA5/VA6 (IC BD M5 PAL)

Controller Port

Connect C9 and C6 to their corresponding controller port pins.

  • Controller port pin 6 is A + B
  • Controller Port pin 9 is C + Start

You can place the wires through the controller connector from the top side of the mainboard and pull it through with some tweezers. This is the cleanest method and much more preferable to routing the wires around the outer side of the mainboard which can result in crushed wires and possible shorting.

CPU Halt (CPU)

Connect the CPU pad to Pin 17 of the CPU.

When this is connected the game will pause when START+A+B+C is held long enough to start cycling through the console’s regions. Only connect this if you want the game to pause when cycling through the regions.

LED Installation

This is the most difficult part of a Mega Drive switchless mod install but it is entirely optional. Without it though, the region of the Mega Drive will be difficult to determine.

Two Types of Top Case LED Fixtures

Removable Bezel and LED

This is the easiest LED to remove because the bezel cover that is holding in the LED can be unclipped. The LED will then come straight out.

Fixed Bezel and Sealed in LED

This is more difficult because the LED will need cutting out from the underside of the top case. The metal legs of the LED will be in the way when cutting the hole. Once the hole is large enough, the LED can be removed.

Removing the Old LED

Remove the wires connecting the motherboard to the top cover. Removing from the top cover requires bending the metal legs of the LED up and then pulling the plastic connector off. The connection to the motherboard will require desoldering.

Cutting the Hole

Side cutters, a hand drill or an electrical rotary tool can be used to cut the hole for the new LED. Then a file can be used to smooth the edges for a neater appearance. Slow and steady is the only way to do this without making a mess. Start in the center and work outwards and do not go too deep to avoid cutting into the bezel.

The hole should be perfectly round and just wide enough so the new LED fits.

Wiring the LED

Custom PCB mod kits will come with a pre-wired female JST connector and a separate LED board with pre-wired male JST connector. Whilst this system was designed to be as easy to install as possible, it still require the permanent modification to the top shell of the Mega Drive.

Fixing the LED

1 – Place the LED into the hole. Check the top side of the case to see how far out the LED sits. If it is too far, a piece of tape over the hole on the top will ensure the LED is positioned correctly.

2 – Remove backing from the adhesive pads of the LED board.

3 – Place the LED board over the LED and press down firmly. My kits will come with LEDs that have Red as the long outer lead. Make sure this long outer lead is placed into L1/L60. Short outer lead will be L2/L50. This will ensure that Red is used for the North American region.

4 – Solder the LED in place.

Note that the adhesive pads can be removed and the board can also be fixed in place with hotglue. This will give the LED more stability, but the adhesive pads will be strong enough to keep the LED in place and are easy to replace if there are any problems, but there may be some movement of the LED. Do not solder the LED whilst the foam tape is compressed in any way otherwise the LED will be sunk into the bezel hole too much.

Jumpers (J1, J2)

Depending on the board revision, these jumpers might not be available. The board will be hard wired to the best set-up.

J1 / Reset On Mode Change – When set to (+) or a +5V source, changing the region via the reset button or controller will have an instant affect on the video rate. When set to (-) or ground, changing the region via the reset button or the controller will reset the console and the new region will be set on boot up.

J2 / Set LED Type – When set to CA or a +5V source, a Common Anode LED should be used. When set to CC or Ground, a Common Cathode LED should be used.