Got a call today about some lights not working in a wood framed storage building, metal siding. There is an outside subpanel (main lug) fed with single phase, 2 hots, a nuetral, no ground, direct burial, 208/120v. Bonding screw is in place, no ground rods. Check voltage and get some weird readings like 200v A leg to nuetral, 0v B leg to nuetral. Turned off all breakers and put on 3 fluke meters A-N, B-N, A-B. Everything looks normal with both legs to nuetral at 120v and A-B at 208v. Turned on a breaker for one 8' HO, viewed the meters and got A-N 30v, B-N 178v, A-B 208v. So I'm thinking I am losing (or lost) the neutral feeding the panel. It is about 300' back to the building where it is tapped from, 100% under asphalt and concrete. Any suggestions as to anything else to check? Is the lack of grounding contributing to this? I'm thinking about trying to megger the N wire, we have a small handheld fluke megger that rarely sees any use.