sorry, I don’t have a diagram (diagrams and user manuals seems hard to get for these oldies). but; my ME-5 took a hard fall to the floor once, which caused the memory backup battery to loosen, all settings where lost. I simply opened the box, measured the battery (small ‘coin’, flat one) to be 3V, and replaced it with 2x standard AA (R6) batteries in a plastic holder (there’s planty of space in there). you don’t need rechargable cells, these big ones will last a long time. still works just fine! and, YES, you must do the battery change with AC power ON to not loose settings. be careful where you lay your hands! regards, HansC