Frequency response of a (Metex)M3800 DMM?

[ppppenguin]

Not to mention eliminating the shock risk between a chassis supplied by the transformer and earth whether test gear is being used or not.

When working with this sort of circuitry I'm really undecided about using an isolating TX or RCD. I understand the arguments for and against, we've covered them in detail in the past. If I touch something I shouldn't and enough current flows to be nasty an RCD will trip. But as Lawrence says, the isolating T will eliminate certain kinds of shock altogether.

Neither will really protect you well against the RF burn you'll get from touching a high frequency, high voltage point. I once touched the collector of a line output transistor and got a small burn on my finger. Not serious, but I only brushed past. It could have been a lot worse.