Disconnect the power supply from the unit.
Wipe down the unit's outer case using the cloth and a small dab of the cleaning solution. Pay particular attention to the areas surrounding the inputs and controls.
Use a cotton bud with some cleaning fluid to clean the recesses under the faders and input switches, and reposition the controls as you go to ensure you clean the areas they were covering.
Place the cushion or towel on your work surface, and lay the unit on it, upside down.
Remove the screws from the underside of the case, and lift the base portion off.
Use the vacuum cleaner to clear out any collected dust inside the case. Take care not to nudge or bump any of the electronics with the tip of the nozzle.
Slide a toothpick around the axle of the cassette spindles, and scrape out the collected dirt and grease. Give it a wipe using a cotton bud moistened with cleaning solution.
Apply a pea-sized quantity of lubricant around the spindle base using a clean toothpick.
Check all the input and output connections for stability by gently wiggling each of the wires soldered to each connection and examining the solder joint for any movement. If any are loose or frayed, melt the solder using the iron, and reset the joint with fresh solder.
Ensure that the metal prongs on the 1/4-inch jack sockets are bent at a sufficient angle to ensure a solid, snug contact when a plug is inserted. If any of them have been forced back, slowly apply pressure to the prong tip using a finger, gradually bending it back to the correct position.
Replace the lower portion of the case, and return the screws to their original places.
Reconnect the power supply.
Place a few drops of the head-cleaner solution on the tape head, insert the head cleaner cassette and play it.