Clean the tip of a soldering iron with a damp sponge. Remove all solder residue and leave it to dry for five minutes.
Turn on the soldering iron so it is hot when you come to use it.
Unplug all connected cables. If there is one, remove the 9-volt battery from the battery-snap. This is typically located behind a plastic shield on the top of the pedal.
Place the pedal face down. Unscrew the bottom of the chassis enclosure using a small Phillips screwdriver.
Turn the pedal over. Lift the top half of the chassis away from the base plate to expose the printed circuit board.
Identify the op-amp chip. It is typically the only board-mounted chip in the circuit. Look for a black rectangular chip approximately the size of a cell phone SIM card. If you have the wiring schematic, use that for reference. Once you identify the chip, measure its distance from the two nearest edges of the board.
Place the pedal face down. Use the measurements you just took to locate the op-amp chip's connector pins. For example, if the chip is located 10 mm from the top and 16 mm from the side, the connector pins will be the same distance away on the board base.
Melt the solder joint fusing the connector pins to the conductor strip on the base of the board. Press the clean soldering iron tip against each joint until the flux rises. Leave the pins to cool off for 10 seconds, then straighten them so that they are perpendicular to the board. Flip the pedal over and pry the chip out of the board turret with your fingers.
Slot the replacement chip into the vacant turret. Turn the board over and press the connector pins so that they lie flat against the conductor strip.
Put a small amount of solder onto the tip of the iron. Press the tip of the iron against the connector pins to fuse them against the conductor strip. Reassemble the pedal enclosure.