Old NTSC TVs can be modified to display PAL signals by tweaking the vertical scan rate, the RF/IF stages and by adding a PAL color decoder board in the right place. Sometimes the external board isn't needed at all, the set's own chassis has the spots to add the missing PAL decoder components, this is especially true of cheap Asian made TVs intended for worldwide export. Countries like Argentina, Paraguay and Uruguay had a lot of experience in modifying US NTSC-M or Brazilian PAL-M imported TV sets into their unique PAL-N standard, as in every TV repairman worth his/her salt could perform such a modification. Russia was in a similar situation during the early 90s, old Soviet-era TV sets were SECAM only, and since Russia didn't have an official video game market consoles entering the country were PAL. A decoder board could be installed by your local TV tech if you wanted to play video games in color on your old TV.
Newer CRT TVs with full microprocessor control (two or one-chip designs) are either NTSC/PAL compatible from the get-go or just need a slight software change to get them to display PAL signals. Again, this is especially true of cheap, mass produced designs intended to cover most of the world's TV standards with few to no alterations. Line voltage is also a non-issue nowadays, most switching power supplies are able to take any voltage between 90 and 260V AC, just replace the plug on the end to fit your outlets.