09-04-2015, 07:58 PM
Well you are making progress. If the hum waveform flattens to a straight line when you short the input, then you are on the right track. It looks like you are just picking up noise from the unshielded portions of the probe or input wiring.
How about when you have nothing plugged into the input terminals? Do you still get the hum waveform when the case is installed? Without the shielding of the case, you may get noise pickup from the sensitive preamp circuitry of the scope input.
How about when you have nothing plugged into the input terminals? Do you still get the hum waveform when the case is installed? Without the shielding of the case, you may get noise pickup from the sensitive preamp circuitry of the scope input.
