This is much more than a DC-DC converter with a wide input range; when they say it is made to accept just about anything as an input, they mean it. Found a working power source but don’t know ...

Schaefer, a manufacturer of robust and reliable power supplies, is pleased to announce the MHVC250 high voltage dc/dc converter. The MHVC250 design features a wide input range of 420VDC to 975VDC ...