I need to probe the primary side of an SMPS in for repair. This side is not mains isolated, and could be hot/live, at around 330V.
My oscilloscope has only a 250Vpk input rating and can only reliably read up to about 100Vpk, so I would at least need a 1:10 probe. However, I don't feel happy connecting a £6 eBay probe to an expensive scope when magic smoke just loves to leak out. Is there a way to make it safer? I guess I could spend some more money on a high voltage probe, but that would cost me more than a new SMPS.
Also, I heard I should get an isolation transformer for the power supply so that I don't short anything out to earth. Is this a good idea? (The power supply is from a TV and does not use an earth pin.)