How do you change a battery in a Yamaha spx90 effects unit?
First of all, does the unit power up and display? I've seen one too many posts recommending a new battery for "dead" equipment. Most batteries are for backing up user modified settings and programs. Most keyboards and rack units (including the SPX90) are fully functional with no battery at all. However, they will return to defaults each time the unit is turned on. Ok, Now that that's settled. --Test the old battery before you remove it. I've had my original SPX90 since 1987 and have never had to replace the battery. --Unplug the SPX90 AC plug from the wall outlet (I know, but you'd be surprised how many people forget this) --Remove the top panel so you can see the battery (2 top screws, 2 screws on each side and 1 screw on back). The battery is on the right front with the unit facing you. Put the positive lead of your multimeter on the top of the battery and the negative lead on one pin of the small resistor just to your left (R238). If it reads 3 volts or above it's fine. If it's below 3 volts continue with replacement. --Remove the bottom panel (6 screws). -- It's a piece of cake from here -- locate the two solder points under the battery (left side front with unit facing down) and remove excess solder with a solder sucker. While holding the soldering iron alternately on each pin, rock the battery until it's out. --Use a solder sucker to fully open the holes on the board and solder the new battery in. Positive side is marked with a + symbol. Make sure it's not backwards. -- After the unit is put back together you need to reinitialize it. --To reinitialize, hold down the foot trigger and balance buttons, and while continuing to hold them down turn the unit on. That's it -- have fun.