SG-1000:Controller Adapters

=Original SG-1000= The original SG-1000 featured a hardwired SJ-200 joystick, which has rather subpar construction and equally subpar ergonomics. Sega even tried to rectify this by releasing the extremely rare JC-100 controller adapter, which allowed for compatible gamepads and joysticks to be used in place of the joystick.

Building a controller adapter
While the JC-100 is near impossible to find, it is possible to construct a comparable adapter out of a 9-pin controller extension cable so that one can not only use SJ-150/151 and Sega Master System gamepads, but also use Genesis/Mega Drive pads, even wireless pads.

Materials required

 * Phillips head screwdriver
 * Soldering iron
 * Multimeter
 * Leaded solder
 * 9-pin controller extension cable, these can be found through a variety of sources
 * Wire cutters and stripper
 * Wire crimper
 * 7-position 2.54 mm pin header with female connectors

Installation

 * 1) Flip over the SG-1000 and unscrew the four screws securing the case. Remove the motherboard from the case and set the case aside.
 * 2) Carefully disconnect the joystick from its pin header on the motherboard and set it aside.
 * 3) Take the 9-pin extension cable and cut off the female end (the end going to the console). The cable can be cut to any length desired, though it is recommend to keep it short.
 * 4) Strip the cutoff end of the extension cable to reveal the individual wires inside, then strip and tin these wires.
 * 5) Using a multimeter and the SG-1000 controller pinout, map out the wires inside the cable and make note of them, as not all extension cables follow the same color scheme.
 * 6) Make note of the pins on the joystick pin header on the SG-1000 motherboard. The pins are as follows, according to the numbering on the motherboard:
 * 7) * Pin 1: Button 1
 * 8) * Pin 2: Button 2
 * 9) * Pin 3: Right
 * 10) * Pin 4: Left
 * 11) * Pin 5: Down
 * 12) * Pin 6: Up
 * 13) * Pin 7: Ground
 * 14) Using a wire crimper, take the tinned ends of the required wires from the extension cable and crimp them with female connectors. Insert the crimped wires into a 2.54 mm pin header connector, following the pinout on the SG-1000 motherboard.
 * 15) Cut off the wire for pin 7 on the extension cable since it will be unused.
 * 16) Connect the completed connector into the pin header on the motherboard.
 * 17) If you wish to use wireless Genesis/Mega Drive controllers, you will need to add 5V in order to power the receiver for these controllers. This will be on pin 5 of the extension cable. 5V can be found on many places on the SG-1000 motherboard, but on some board revisions, there is a very convenient jumper located between the joystick header and the channel select switch.
 * 18) Solder the wire going from pin 5 of the extension cable to a 5V source on the motherboard. If necessary, an extra wire can be added if the wire from the extension cable is not long enough to reach.
 * 19) Although optional, it is recommended that a grommet be fitted where the extension cable exits the SG-1000. This way, the cable will not suffer possible abrasion damage.
 * 20) Test with a known working 9-pin Sega controller. If all works well, reassemble the SG-1000. Now *all* 9-pin Sega controllers will work on the SG-1000, including wireless controllers! As with the Master System, buttons B and C on a Genesis/Mega Drive controller correspond to buttons 1 and 2 respectively.

=SG-1000 II= Released a year after the original, the SG-1000 II was a cosmetic redesign which attempted to improve the ergonomics and functionality of the original. The most notable way in which the SG-1000 II accomplished this is that it did away with the hardwired joystick and replaced it with a proper 9-pin controller port. In addition to the SJ-150 and SJ-151 gamepads, the SG-1000 II's controller ports also work with the SJ-200 and SJ-300 joysticks as well as the Mark III's SJ-152 controllers and Sega Master System pads.

However, Genesis/Mega Drive controllers do *not* work with the SG-1000 II. For unknown reasons, Sega grounded pin 7 of the controller port on the SG-1000 II, which holds the multiplexer inside the Genesis controller low and prevents it from functioning as intended. To use Genesis controllers with the SG-1000 II, pin 7 on both controller ports needs to be isolated. This can be accomplished by severing the thick trace going to this pin, or by desoldering the controller port and physically cutting off the pin where it goes into the motherboard.

=Links= https://nintendosegajapan.com/2015/12/29/adding-a-sega-controller-adapter-to-an-original-sg-1000-home-made-jc-100/