My lovely wife kindly bought me six vintage games consoles for Christmas 2023, all in unknown or non-working condition, including my first SEGA Master System II.
The SEGA Master System II is as a cost-reduced version of the original Master System, with several components removed to reduce cost: the Sega Card slot (used for flat cards and 3D glasses), reset button, power LED, expansion port, startup music and logo, and – in most regions – the Master System’s A/V port was omitted, leaving only an RF output.
Master System IIs aren’t particularly rare, and you can pick them up in non-working condition for quite cheap – they go a bit more when refurbished and modified, though. Their nostalgia value and interesting game library make them quite collectible.
On its arrival, it seemed to be in quite good physical condition. I couldn’t test it yet unfortunately though, due to it only having an RF video/audio output, as I don’t have a TV with an analogue tuner any more. I needed to modify it beforehand.
The first step was to disassemble the unit and check over everything inside.
Disassembling the SEGA Master System II
The Game Gear is easy to dismantle with basic tools: there are five Philips screws holding the bottom case in place, around its perimeter.
With the case opened, you get your first look inside the console – everything seemed to be original and pretty much untouched.
The mainboard is held into the bottom case and the RF shielding with five Philips screws around its perimeter, two Philips screws on the voltage regulator, and two Philips screws on each side of the cartridge port.
RGB Video Modification
The Master System I had an RGB video output via a DIN connector, and this was dropped on the Master System II for an RF modulator only – this has quite a poor image quality and isn’t compatible with modern displays without some kind of converter box.
Thankfully, several modification kits are available to reinstate a MegaDrive II compatible RGB video output in place of the Master System II’s RF modulator, without any case modifications required – I bought a modification kit from ConsolesUnleashed, and an RGB SCART cable from RetroGamingCables.
The RGB kit is relatively easy to install, following the manufacturer’s comprehensive installation guide – the most difficult part is probably removing the original RF modulator, as this requires a high-powered soldering iron due to its significant thermal mass.
The installation of the DIN connector shield to the new AV brace also requires a high-powered soldering iron, again due to its thermal mass.
Region Free Modification
There are also several modification kits available to allow a Master System II to work with multi-region games, without any case modifications required – again, I bought a modification kit from ConsolesUnleashed.
The region-free kit is relatively easy to install, following the manufacturer’s comprehensive installation guide – the only unusual part is modifying the original power switch to add a light pipe for the board’s status LED (which also acts as a very useful power LED), which requires drilling a 3mm hole in one side using a stencil provided with the kit.
Mainboard Servicing
After the modifications, I wanted to do some preventative maintenance on the mainboard – this included replacing all of the aluminium electrolytic capacitors, fitting a new 2.5mm DC jack as the original was quite corroded, and replacing the original 7805 linear voltage regulator (5Vdc @ 1A) with a drop-in modern equivalent (the TSR-1-2450, which runs cool and doesn’t require a heatsink.
Aluminium electrolytic capacitors are commonly used for filtering, smoothing, and decoupling in both high- and low-voltage electronics. They typically comprise aluminium windings which are coated with a liquid electrolyte, which can dry out over time (negatively affecting the performance of the capacitor, often causing them to fail dead-short), or leak out and cause corrosion to the PCB and surrounding components.
There are several production variants of the Master System II mainboard, each of which have different electrolytic capacitor values and locations, so take note of which you have.
This one is an early PAL board, marked “171-5922-A”. This is easy enough to recap as it only has 15 through-hole electrolytic capacitors:
- CE: 10uF 16V
- CE: 10uF 16V
- CE: 10uF 16V
- CE: 10uF 16V
- CE: 10uF 16V
- CE: 10uF 16V
- C18: 10uF 16V
- C31: 1uF 50V
- C32: 10uF 16V
- C38: 100uF 16V
- C41: 100uF 16V
- C42: 100uF 16V
- C43: 100uF 16V
- C44: 47uF 10V
- C54: 10uF 16V
I couldn’t find any commercially available capacitor packs for this version of the Master System II mainboard, so I just made up my own by noting the specifications of all of the electrolytic capacitors on the board, and ordering a set of high-quality known-brand parts.
When substituting electrolytic capacitors, the capacitance needs to be the same, and the voltage rating can be the same or higher (within reason) – when you’re going through all this effort to recap something, be sure to use high-quality replacements.
When fitting new electrolytic capacitors, you must take care to ensure that the value, voltage rating, and orientation of the new capacitor are correct – electrolytic capacitors are polarised, so must be installed the correct way around, else they’ll get hot when powered on (and probably explode). The polarity is marked on the case: for aluminium electrolytic capacitors, the negative side is usually shown by a white stripe (for through-hole) or a black bar (for SMD); for tantalum capacitors, the positive side is usually shown by an orange or white bar (for SMD). This catches a lot of people out!
You can’t always trust the orientation markings on the PCB silkscreen (if it even has them, not all boards do), as sometimes mistakes were made in the design from the factory (take the PCB layout of the audio circuit on the Commodore CD32, for example), so care must be taken to match the orientation of the new capacitor with the original. Make sure to take lots of “before” pictures for reference, and double-check throughout.
I usually remove each capacitor one-by-one using my desoldering station, then immediately install its replacement part – this minimises the likelihood of getting it wrong. The board should then be thoroughly cleaned to remove any leaked electrolyte and leftover flux, using isopropyl alcohol and an ESD-safe brush.
I also cleaned all of the sockets and controls using contact cleaner.
Reassembly and Testing
The console reassembly is just the reverse of its disassembly.
After its modifications and preventative maintenance, the Master System II looked great and worked perfectly! This seems to be a console with Alex Kidd in onboard ROM, whereas some consoles had Sonic the Hedgehog instead.
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