If your Master System is having issues, check the below general troubleshooting information for help.
No Power LED
Open the console and check the 7805 voltage regulator underneath the metal heat sink with a multimeter. With the front of the 7805 facing outwards, the left pin is input voltage (generally around 9-10V DC), the middle pin is ground, and the right pin is output voltage (5V DC). Early Master System consoles (837-6067 revision for NTSC, 171-5385 and VA1 for PAL) do not have any reverse polarity protection, so plugging in a power supply with the incorrect polarity (tip positive instead of the proper tip negative) can damage the 7805. This is one of the most common failure points of the console.
- If no leg has around 9V, check your power supply and maybe try a different one. Also check the power jack for any signs of damage, corrosion or failed solder joints. The power jack used in the SMS is a standard 5.5 x 2.1 mm barrel jack and is an inexpensive and commonly available part.
- If no leg has around 5V, replace the voltage regulator with a new 7805 voltage regulator.
For early Master System consoles, it is recommended to install a diode on the power input to prevent the 7805 from being damaged by an incorrect power supply again. Locate the ferrite bead marked "JV" near the power jack, desolder it, and solder a 1N4001 diode in its place, with the cathode (striped end) pointing towards the front of the console. Later board revisions incorporated a diode for reverse polarity protection.
Black Screen
If the console powers on but only displays a black screen, check the following:
- Check that the prongs on the top RF shield near the expansion port are not touching the expansion port pins on the board. If they are, either bend the RF shield away or cover the expansion port pins with kapton tape. This port was never used by official accessories, but aftermarket accessories may be used in that port such as the expansion port BackBit Pro cartridge variant or the SMSFM modification board.
- If the Z80 or VDP (marked 315-5124 or 315-5246) are getting excessively hot within moments of being powered on, that may be a sign that either one of these chips has failed and is preventing the console from booting. The Z80 is a generic part, but the VDP is a custom IC and may be difficult to source.
- Check the board for any signs of broken or corroded traces.
- For the Mark III, check that the game contacts and the cartridge or card connector are clean. This console does not have a BIOS and will display a black screen if it doesn't detect a game.
Games Not Working
If you're trying to play a game but are only getting the built-in game or a "Software Error" screen, check the following:
- Make sure the game contacts and cartridge or card connector are clean.
- NTSC model 1 consoles with a built-in game (model numbers 3010-A, 3010-B or 3010-C) have components that are only soldered down on one side, including both the cartridge and card connectors. Over time, these connectors can develop broken solder joints, which can prevent the console from reading any game. Inspect the solder joints for these connectors and reflow them if they appear broken. Broken solder joints will appear as a dark ring in the joint.
- This also applies to later NTSC model 1s with the v1.3 BIOS and the Japanese Master System (model number MK-2000).
- Check the cartridge or card connector for any signs of corrosion or damage.
- If all else fails, check the board for broken or corroded traces.
- Note that international consoles are not compatible with SG-1000 My Cards and some Japanese My Card games, and these will display a "Software Error" message instead of booting. This is due to them failing a header check in the BIOS and can be bypassed by performing a BIOS mod.
Light Phaser Issues
The most common issue with the Light Phaser light gun is a broken cable. You can order a replacement Genesis controller cable, use a multimeter to test which wire corresponds to each pin on the connector, and swap the old cable for the new one.
If you have a flash cart, you can boot SMS Light Gun Test.sms from this zip file created by Ben Ryves. This will show the tracked location on-screen, showing if it's present at all or if it's mis-aligned — which generally can be fixed by opening the gun and aligning the sensor module.