I want to make a 0–300V variable DC power supply (max current 100 mA). I found this design,
which features a 1:1 transformer across the mains for some sort of safety reasons. However, I couldn't find any 1:1 120 VAC transformers that weren't incredibly expensive. Next I looked at this circuit,
which uses a light-bulb "in order to provide ultimate safety in case of a short circuit or a component failure."
I'm not myself able to ascertain if the correct design precautions are being observed in either of these circuits. The second claims to be lethal to the touch.
My question is: does this second circuit exhibit any obvious safety-related flaws in its design (besides, perhaps, contact lethality)? If so, what is the cheapest method of achieving a 0–300V variable power supply while observing all relevant safety considerations, and will any DIY implementation be, to some extent, inherently dangerous?