About Waveforms In Equipment
When you perform the electronics troubleshooting work, having a service manual or schematic diagram is an added advantage. The sample waveforms listed in the manual could quickly helps you to pin point the fault fast. Of course not every troubleshooting job need an oscillscope to locate the fault but if you are facing troubles in a tough dog repair then you should need it.
I believe you have downloaded some service manuals from internet before and if you carefully observe those waveforms, you would see that those waveforms actually taken from critical test points. Not only that, the waveforms result are in peak to peak voltage (Vp-p) and not in frequencies and etc. This mean that if a good waveform have 12 volt peak to peak anf if you got only 6 or 7 volt peak to peak then you have to pay a special attention on that test points or circuit. Any bad component in that circuit could change the result of the peak to peak voltage.
If you don't get that exact waveform or the waveform in different shape then this mean the particular circuit have problem and you need to concentrate on that area.