[Amps] 3-500Z viable after long storage?

[Jim Barber]

The Henry 3K-A I just picked up (loooonnnggg drive!) has a set of what 
were 12 years ago "fresh" 3-500Z's with it. The amp and tubes have been 
sitting in the OM's nice, warm, dry shack for 12 years with no power 
applied. He never got around to pulling 240V into the new shack after he 
moved.

The question is should I try them? There's no high-pot tester available 
locally that I know of. My fear, of course is that one or both might be 
gassy and flash over, potentially damaging the HV supply.

Thanks,
Jim, N7CXI