Bronson++ isolation transformer (MII 2000) teardown with a variable transformer (VC 3000)

An isolation transformer and a variable transformer are handy, if not necessary, devices when working with main voltages on the bench. In this video, I will show how the Bronson MII-2000 isolation transformer works with VC-3000 variable autotransformer of the same company.
The isolation transformer is capable of converting 120V input to 240V output but it works also as 1:1 transformer when fed 240V AC. We used the variac to test it under both conditions.

[@djsbriscoe]

Is the "Isolation transformer" REALLY isolated? Maybe you should do a REAL teardown to make sure. I've just bought a M11-3000 version and the ON/OFF switch had a wire link soldered across it that was missed during any"QA" inspection. This meant the unit was ON permanently. I corrected this fault myself, so now it at least turns off. Mine really does need a COMPLETE teardown to make it safe. It is so bad that Amazon UK don't want it back, and they refunded my money.

[@asserslab]

@djsbriscoe: Thank you for your word of warning! I wonder what has been the motivation for the link you mentioned. Is it possible that you've obtained a second hand item and it was originally used somewhere where the link was used to ensure that the device was not turned off by accidentally pressing the button?
I double checked my MII 2000 transformer and I got no current flow between the primary and the secondary circuits when the device was turned on. The case grounding was working perfectly fine too. Still, I have not measured the actual dielectric strength of the coil insulation.