My lovely wife kindly bought me my first Nintendo Entertainment System (NES) for my birthday back in 2023.
The NES is an 8-bit third-generation home video game console, first released in Japan in 1983 as the Famicom, then to the rest of the world in 1985 as a redesigned version: the NES. After developing a series of successful arcade games in the early 1980s, Nintendo planned to create a simple, cheap home video game console that ran games stored on cartridges. The NES was one of the best-selling consoles of its time and helped revitalize the US gaming industry following the video game crash of 1983.
NESs aren’t particularly rare, and you can pick them up in non-working condition for quite cheap – they go for quite a bit when refurbished and modified, though. Their nostalgia value and interesting game library make them quite collectible.
On its arrival, it seemed to be in reasonable physical condition. I powered it up using the original PSU that it was sold with, connected to a TV using RCA cables for composite video and mono audio, and with a game cartridge installed – it didn’t start up correctly, instead the power LED blinked and video flashed between a blue and black screen.
This is apparently a common problem with PAL NESs, due to cartridges not making proper contact and the lock-out chip automatically resetting the system.
The first step was to disassemble the unit and check over everything inside.
Disassembling the NES
The NES is easy to dismantle with basic tools: remove the six Philips screws around the perimeter of the underside of the case.
With the case opened, you get your first look inside the console – everything seemed to be original and pretty much untouched.
The upper RF shielding is held in place with seven Philips screws.
The cartridge shield is held in place with six Philips screws, and the motherboard is held in place with three Philips screws.
The cartridge connector simply slides off the mainboard.
Flashing Red Light Repair
A constant reset is apparently a common problem with PAL NESs, due to cartridges not making proper contact and the lock-out chip automatically resetting the system.
The original cartridge connector seemed to be quite corroded and quite loose, so I decided to replace it with a high-quality modern 72-pin replacement connector.
I also cleaned up the connectors on all of my NES cartridges with cotton buds and 99.9% IPA – testing again, the console seemed to work OK.
At this point, I wanted to do some preventative maintenance on the mainboard.
Mainboard Servicing
With the console working again, 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 are quite cheap in comparison to their solid-electrolyte counterparts (such as tantalum and polymer electrolytics), so are very common in consumer electronics.
Their useful lifetime is highly dependent on the specific application that they are used in (i.e. frequency, ripple current) and temperature, as well as the manufacturer and series of the specific component. 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 even leak out and cause corrosion to the PCB and surrounding components.
There are several production variants of the NES mainboard, each of which have different electrolytic capacitor values and locations, so take note of which you have.
The NES mainboard is easy to recap as it only has 3 through-hole electrolytic capacitors:
- C1: 100uF 6.3V
- C9: 2.2uF 50V
- C23: 1uF 50V
The trickier part to recap/rework is the combined RF modulator and PSU module, which needs to be desoldered from the mainboard for servicing, which requires a high-powered soldering iron due to its significant thermal mass.
- C3: 10uF 25V
- C25: 2200uF 25V
- C26: 100uF 16V
- C29: 100uF 10V
I couldn’t find any commercially available capacitor packs for this version of the NES mainboard/PSU, 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.
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.
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.
Region-Free Modification
The NES is region locked using a “NES10” lockout chip, which checks the key inside a cartridge, determines whether the software is suitable for the system, and resets the system if it is not – this is also what causes the “red blinking light” issue when a cartridge doesn’t make proper contact, where the lockout chip constantly resets the console.
This can be easily bypassed in a non-destructive, reversible manner by fitting two jumper wires to disable the lockout chip – this allows the console to play cartridges from any region, and prevents it from constantly resetting when a cartridge is not connected.
Reassembly and Testing
The console reassembly is just the reverse of its disassembly.
After its modifications and preventative maintenance, the NES looked great and worked perfectly! I even bought an SD card cartridge to try out even more of its game library.
I’ve been enjoying all your Nintendo stockpile fixes. What a thoughtful gift from your wife!