I have repaired many NES games over the years and with the exception of a Zelda 2 cart that had been submerged in a flooded basement for several weeks I was never unable to fix any of the games I worked on. Most of this is really due to the fact that NES games were built extremely well, overall their PCB is extremely simple but most importantly its difficult to damage to the point that it cannot be repaired. Unless of course you count someone purposefully trying to damage it to that point.

That being said, most of the time the fix is to clean the pins on the game cart. I would say this is probably the fix for 90% of games I come across. Now some more than others do end up with rust/corrosion on the pins and it requires more detailed cleaning. Out of the remaining 10% of games I would say 5% of them had a leaking save battery that needs the damage cleaned up, which in my experience usually just ends up being minimal damage to traces or soldering joints around the battery and is quick to repair. The other 4% end up requiring traces to be rebuilt, pins to be repaired or capacitors to be replaced. After all these games are going on 40 years old now and capacitors don't last forever. The remaining 1% have significant damage from water and in my experience usually were stored in a basement that flooded.

Well today I came across Amagon for the NES. The individual selling this game cart wanted $5.00 for it and told me it didn't work. He didn't offer any details except that he had tried to clean the pins and it didn't help. I remember playing this game at a friends house when I was a kid. I mostly remembered it because it kinda has these goofy, cartoonish graphics. That being said I was curious what might be wrong with the cart as the outside of it appeared to be pretty clean and in good condition. See pictures below:




The game will not load. It simply displays a blue screen, see picture below:



Upon opening it, I saw a very clean and in great condition circuit board. There were no obvious signs of what the problem was and why this game didn't work. See the PCB below and how nice it looks. Sure the pins have some wear, but almost all these games from the NES era exhibit some wear and the pins on this game are only lightly worn.




I started by inspecting the circuit board with a microscope. This is typically what I do first because as it turns out the naked eye isn't great at inspecting circuit boards or components. I have a detailed video of the full repair attempt posted below for anyone who is interested in seeing first hand what everything looks like.


What I checked & tested on the cart:

- Cleaned pins with deoxit
- Verified all traces are connected and working with multimeter
- Tested capacitor with multimeter and it tested good. Honestly I am surprised!!!
- Inspected board with microscope and found several solder joints that were questionable and repaired them
- Threw my hands up and thought deeply about what the heck could be wrong with this game 


Some details about what has been done up to this point. I cleaned the pins with deoxit and a magic eraser until they were shiny and had no pitting or corrosion left on them. I do not believe there are any issues with the pins. Using a multimeter I have triple checked all the pins connect where they should on the PCB. I removed the capacitor and measured capacitance and it measures 26uf (uf is microfarads) the label on the capacitor indicates that its a 22uf. Keep in mind the capacitors used in NES games have a tolerance of 20% so 26uf is within this tolerance margin and means the capacitor is good. If it were not good it would measure significantly lower than 22uf. The reason why I removed it from the circuit board is because when a capacitor is installed you will often get inaccurate readings that are unreliable. For example when its installed on the board my multimeter reads that its capacitance is 89uf.

I have inspected all the solder joints and traces on the board multiply times. I did find some poor joints that on a multimeter had good continuity, but because there was pitting and pockets I did reflow the solder to fix it. Unfortunately this game still doesn't work. I am still only getting a blue screen.

At this point I have tested all components except the ROM chip. It is possible for the ROM chip to be bad and thus the game will not work unless that chip is replaced. This is unfortunate because its the 1 part that isn't repairable without having a donor chip from another Amagon game. In 20 years I have not seen a single bad ROM chip, I wonder if they are that rare or if I have just been lucky.

Well tomorrow is another day. I refuse to give up on this guy and frankly I just want to know what is wrong because this game doesn't appear to have any reason not to work. 

 
Update 9/18/2024....

I retraced my steps to double check everything I previously did. The end result is the same. I believe the rom chip, eprom or maskchip (not 100% sure what the correct name is, since I have heard these used interchangeable) is bad on this game. I will be posting a video shortly with the full repair attempt. It shows all the steps I took to test the PCB/components.

At this point I will be keeping the game and in the future I want to revisit this one to test and validate that the rom chip is actually bad. I know I can use a universal eprom programmer to do this, but I don't know if I want to invest the money to purchase one for a single game that likely has a bad rom chip. That being said I am considering purchasing a 2nd, working copy of Amagon and swapping chips. I believe this would also test and verify my theory of the chip being bad as the blue screen problem should follow this chip to a new PCB. So stay tuned for that. If anyone knows a better way to test/verify a rom chip is working I am all ears.

Just a small update. I did end up finding a 2nd copy of Amagon    at a local retro game store. Cost me $10.00. It does in fact work as I have already tested it. I will be doing a follow up video so we should be able to get to the bottom of what was wrong with the first copy and why it only displays a solid blue screen.

Today is the day we find out what is wrong with this game. As I already stated I have a working copy and the plan is to swap the ROM chips to see if the dreaded blue screen follows the chip to the working PCB. If it does then that means the ROM chip is bad and that is why we only get a blue screen. Additionally if the working games ROM chip repairs the non-working copy of the game that will prove the PCB/other chips are all functioning.

See the picture below. The chip outlined in RED is the ROM Chip we will be swapping...

Jinkies!!! 

Moving the ROM Chip from the working game cart to the non-working game cart, repaired the game and it is now working. So the ROM chip is indeed bad. I soldered it on the working cart and the blue screen followed the chip. I will hang on to this copy of Amagon as it could be useful in the future for another repair. I might even decided to pickup an Eprom programmer and one of the compatible ROM Chips on the market and repair this game by replacing the ROM Chip. I would need an Eprom programmer in order to write the games data to the chip before soldering it to the board, but that is an entirely different project for another day.

Results: Blue screen on an NES Cart = bad ROM Chip. All the other chips on the game were verified working when I swapped the ROM chip only and it now worked. 


For those who would like to see the full repair video it will be posted in a couple days. 

Video will be live 10/4/2024 at 8AM Eastern Standard. Video shows the troubleshooting steps I took to identify the bad chip on the game. This is an alternative and inexpensive method of doing this for  less expensive games. For more valuable games this method is probably not favorable and the better method then would be to get an Eprom programmer and test the ROM Chip using that.

Enjoy