Don't mean to necro an old thread, but I couldn't find this info anywhere, (that and I can't read schematics), lol but this thread pops up when you search any form of "LM3900 Nintendo" in google so I figured it would be best to add it here...
My point is: the lower LM3900N located at N5 is for the RIGHT side game of the Vs. pcb. The upper LM3900N (at R5) is for the LEFT side game, (when looking at the board with the edge connector up). I know this because I recently had a board with a bad one and by trial of elimination I popped the lower one off and the back side of my tent stopped emitting (very poor, low) sound. replaced the chip with a new one and it was back to normal.
Also, I don't think it would hurt to socket these chips before replacing them, they kinda suck to remove, even with a proper desoldering gun.