In order to test any type of components or electronic products, you need the right equipment to do the testing with. The test equipment you will need includes a digital multi-meter, oscilloscope, signal generator, and portable power supply. A digital multi-meter is one of the most important and used testers for electronic testing. The multi-meter should provide voltage, resistor, diode, and transistor testing. As for a signal generator - this is used to produce a tone in the audio circuit when the equipment is turned off so you can find out if a signal is getting through the circuits. If you hear a tone in the speaker of the generator, you know it is working. If you don’t, there is something wrong with a component in the audio circuit. An oscilloscope is good to look at wave patterns in circuits. If you know what a pattern is supposed to be, based on the schematic and technical manual, and the scope does not show this, you know that circuit or the preceding one is faulty.