Capacitor on backside of Exodus Ultima NES cartridge pcb

[Luke4409 0]

I recently picked up a copy of Exodus Ultima for the NES and when I opened it up to clean it I noticed this capacitor was on the back of the pcb and I've never seen that before. It looks like somebody soldered it in at some point but I have no idea why. Does anybody know why this would be there or if some NES games have this and I've just never seen it before?

[LeatherRebel5150 915]

I've seen it before in a bunch of different games. I think iI asked about it many years ago and the consensus was it was either a game that sent back to be repaired or a mistake in design where that was the easiest fix. What exactly it does function wise  I don't know

[Ice Man 14]

This is just a fix to keep SRAM voltage steady to avoid corrupted writes when power is off.

Usually 22uF decoupling caps are added between VCC and GND on the main board and also another 22uF between SRAM VCC and GND as seen on most boards that have SRAM.

Edited March 26, 2020 by Ice Man

[gusgc360 0]

I just opened a copy of Ultima Exodus and it has the exact same capacitor in the same spot. Basically our pcbs look exactly the same. From what I've heard consulting different sources, it is a sort of "quick fix" in this particular revision of the board.

If you look for the Ultima Exodus pcb online on NES archives, you'll find that most copys have two capacitors in the front of the pcb, but both your copy and mine only have one capacitor by design. That leads me to believe that the capacitor on the back is somehow compensating for the capacitor that was added on later revisions. Again, I'm no expert but this is my recollection of the info I found online.