Percussive maintainance is a technique used to pin down intermittent problems in electronic and mechanical devices. It is very good at tracking down faults affected by thermal expansion: dodgy solder joints, badly fitting components, damaged wires, loose screws, etc. The essence of the technique is to remove the cover from the device, switch it on, wait for it to display its unwanted behaviour, and then poke it with the stick until it stops.
A good (but not foolproof) test of whether percussive maintainance may help you fix your device is to wait for the device to malfunction, and then hit the case at various points with your fist. If hitting it in a certain point solves the problem temporarily, this can give you a clue as to where to start probing. If hitting it doesn't solve the problem, probing still may - many components are too isolated from the case to be affected by blows to its exterior.
Tools required to perform percussive maintainance:
- A non-conductive rod, as long as is comfortable (fiberglass is ideal, wood is acceptable)
- (optional)One cardboard tube, as long as is comfortable
- Whatever is necessary to safely open the case (screwdriver, spanner, plastic scribe, etc.)
The rod is essential, and it must not be conductive. Randomly probing a device with your finger is a good way to get it caught in something, or get yourself electrocuted. Probing with a conductive rod actually increases your risk of electrocution. The cardboard tube can be used to track down components that are producing unwanted noise: rather than probe randomly with the rod, hold one end of the tube to your ear, and move the other end of the tube around until you've located the noisy component. Then poke it with the stick to see if it quietens down.
If poking the component with a stick solves the problem temporarily, there's a good chance that lubricating, resoldering, tightening or replacing the component will solve the problem for good. If poking doesn't help, chances are the fault is not mechanical, and you'll need to use a more sophisticated technique.