Used Oscilloscope: Buy

Look for a rate at least 2.5 to 10 times your bandwidth for accurate waveform representation.

Connect a probe to every channel and attach it to the built-in probe compensation output (usually a small metal tab on the front). You should see a clean, steady square wave. buy used oscilloscope

Deeper memory allows you to capture longer time windows while maintaining a high sample rate, which is crucial for finding intermittent glitches. Look for a rate at least 2