@jpm would I put 400V into a $47 oscilloscope?

Yes, yes I would. From a distance. In a non-flammable location. For funsies only.

@jpm There’s no way in hell you’re getting a Keysight oscilloscope for 50 bucks. 😳

@jpm 250kHz is more like a sound card than an oscilloscope. The cheap student scopes we had at school in the 1980s went up to 20MHz.