Neon Sign Repair.  I have a large neon channel sign on a store front. 
The first couple of letters (run by a 15 Kv Transformer) are dim and
flickering, and the rest are totally dark.  I replaced the
transformer, and nothing changed.  The current transformer has GFI
that is not tripping, and the LED on the unit reports normal service. 
The sign is 5 years old. The neon is totally enclosed in the sign
casing, protected from elements.  I don't see any visible problems
like broken wires or electrodes.  My question is should I completely
rewire the sign, in hopes of that solving the problem?  Is it possible
that a sign of only 5 years old has already had its gasses
contaminated or leaked out?    What would be a "next probably cause"
that I should pursuit?

fiber optics... neon makers nightmare,cheaper, less voltage and you can see it 
from 500 ft,no maintenance no service calls.