I recently picked up a NTSC-U version of Final Fantasy II that was listed online cheaply because the game wouldn’t save which is a fairly easy fix so I picked it up!
Indeed it is not saving, but anytime I get a new cartridge in that has a battery backup I open it up and replace the tabbed CR2032 anyway. So no big deal and lets open her up:
Everything looks legitimate so time to remove the battery which came out very easily (take note of this):
And now battery replaced with a brand new Panasonic tabbed CR2032 battery:
The battery should be capable of holding a game save in SRAM as long as its voltage hasn’t dipped below 2.8v and a brand new battery should measure around 3.2 to 3.3v.
So out of curiosity lets check the old batteries voltage:
WAIT!!! WHAT??? Why is the old battery measuring 3.353v?
That is like new and shouldn’t be having any issues!
So the way the battery backup saves work is that the Memory Mapper chip has an additional function built in that detects voltages on your cartridge. When there is a drop of voltage below 5v it switches the SRAM into a low power state and starts to supply it with 3v from the CR2032 battery to the CE1 (chip enable) pin. When the cartridge regains power again from your console the 3v supply from the CR2032 is suspended and the SRAM is powered normally via its VCC (power input) pin at 5v.
I made a simple diagram below:
From this it is easy to diagnose any additional problems by following the steps below:
- Check for 3v at the MAD-1 Input pin. (Check for broken trace from the battery if 3v is not present)
- Check for 3v at the MAD-1 Output pin. (Replace the MAD-1 IC if 3v is not present)
- Check for 3v at the SRAM CE1 input. (Check for broken trace from the MAD-1 if 3v is not present)
- Check for 3v at the SRAM VCC input. (Replace the SRAM IC if 3v is not present)
After testing it looks like everything is working as it should:
This leads me to believe that either a previous owner attempted to change the battery but didn’t do a good enough job of soldering in the new tabbed battery or that a solder joint on the battery was cracked from a drop of some sort.
I didn’t think to check the batteries connection in advance and simply removed it as usually these batteries tend to be near end of life already.
So I re-assembled the cartridge and made a save, turned off the power, then many hours later turned back on my Super Nintendo and my save file was still there:
SUCCESS!
Hopefully the extra unnecessary information for this repair will help others.