This means checking all electrical connections are sound and all the moving parts a tight and lubricated.
The most important bit also is the detent:
Detent - The detent is a rubber bladder inside the metal sleeve shot tube that regulates the ball machine's air pressure. Replace your detent if the ball ejects with reduced speed or if it frequently becomes trapped.
Well mine has been in the machine for 5 years so it's getting replaced anyway.
The only tools you need to replace the detent are: Electrical tape and an Allen Key.
The job take 10 mins and all the parts can be purchased from: Apollo Leisure
Update: just spent two hours with my ball machine WOW ! The difference the new detent has made, fires the balls on the exact same spot every time, the power of the balls is back to it's 70 mph (yikes!)
Really back to as it was when new!