13th July 2019
Repair

Fixing a Pokemon Cartridge with Corrupted Graphics

Given the age of the original Pokemon series, it is unsurprising to find an increasing number of faulty cartridges.

One of the more common faults, is the issue of corrupted graphics, preventing all or part of the game world from displaying correctly.

Cartridge with corrupted graphics
Pokemon Yellow cartridge, showing corrupted graphics.

There are a few reasons this can happen, and is usually straight forward to fix.

Dirty Contacts

The first thing to check for pretty much any issue with a cartridge game, is the state of the connector on the edge of the cartridge.

Over time, these contacts can become dirty, preventing certain connections between the cartridge and the console from being made.

The best way to clean these contacts is to first blow into the housing, to free and remove any loose dust and debris. Next, gently rub the contacts with a cotton bud, soaked in IPA (preferably 95% or above). This is a sure way of removing any grease or residue from the contacts.

If the issue still persists, it's time to open up the cartridge - for this. you will need a 3.8mm gamebit screwdriver.

Cold Solder Joints

Over time, the solder joints on the board will oxidise and weaken, which can eventually lead to a break in the connection.

To fix this, use a soldering iron to reflow the solder joints on the three main ICs on the board. It is best to apply flux to the joints before reflowing, to ensure a strong joint is created.

Open cartridge
Reflow the pins on all ICs, except the 8 pin IC in the top left of the cartridge (this is the timekeeping IC, so wouldn't cause corrupted graphics).

Using a multimeter, you can check for continuity between the pad and the leg of the IC, which is an easy way to identify any problem areas.

If all of the pins are showing continuity with the pads, and the issue remains, you're looking at a more severe issue.

Faulty SRAM

The SRAM in the cartridge is the next culprit. Although SRAM usually has a long lifespan, the age of the cartridge, combined with heavy usage and improper storage, can increase the chance of failure.

In addition to being used as RAM, the SRAM IC is also used to store the game's save data. As SRAM is volatile, it must be powered at all times to retain data. This means that the IC is always powered on, providing the battery in the cartridge is not exhausted. This further reduces the lifespan of the IC.

Fixing this will require a replacement. There are two options to consider when choosing a replacement - either a like-for-like swap with a new SRAM IC, or an upgrade to a non-volatile FRAM IC. The advantage of using FRAM is that the save battery is no longer required, as data is retained when the IC loses power. The disadvantage is a much higher cost, limited availability, and potential incompatibility.

If you are interested in upgrading to FRAM, check out this post where I upgrade a Pokemon Yellow cartridge.

The replacement part must have a capacity of 256Kb, split into 8 banks of 32Kb, run at 5V, and be packaged as a 28 pin SOIC. I chose the Lyontek LY62256SL.

It is not worth paying extra for a part with a faster access time, as the 70ns of this part is still faster than the two-decade old original.

Lyontek LY62256SL
The Lyontek LY62256SL replacement SRAM IC.

There are several methods of removing the old chip, the easiest being the use of a hot air gun, suchas as the Atten 858D+. This will allow the solder on all of the pins to be heated at once. If you do not have a hot air gun, you can desolder and lift each pin in turn using a soldering iron.

A third option is to cut the legs of the IC, remove the chip body, and desolder the remaining legs.

Once the old chip is removed, the new one can be soldered in its place. This can be done either with a hot air gun and solder paste, or using a soldering iron to apply solder to each pin in turn.

New IC Installed
The new SRAM IC is now installed, ready for testing.

Before testing, it is useful to check continuity on each pin with a multimeter, to check that there are no issues with the installation.

Testing
The corruption issue is now fixed.

The corruption should now be fixed. What do you think about that, Pikachu?

Pikachu
:(

Stupid rat...

Next Steps

If replacing the SRAM has not fixed the problem, there is not much that can be done. The next culprits would be the ROM (the large chip on the right-hand side), or the small, square MBC.

A new ROM chip would need to be flashed with a copy of the game, which would require a programmer. Meanwhile, the MBC is a custom part, which would need to be sourced from another cartridge.

Either way, at this point, it would be easier to purchase a new game, and use this one for parts.

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