[Amps] Lamps and surge protection

[Harold Mandel]

John,

When  testing transformers in my younger days I remember
learning to not touch the winding conductors even though it
was just a multimeter's test voltage being applied.

Perhaps the connection from an inductive device is
providing some sort of energy spike in the 6.3 v.a.c. 
transformer supply that isn't there in the other supply?

Hal

[snip]
One of my amplifier PSCUs has six meters on the front panel, each backlit
via two small 6V wire-ended bulbs. These are fed from an internal rail which
ramps up to +5V in about ten seconds or so. This PSCU has been in regular
service since 1980 and none of its meters have yet needed a bulb change. A
low-voltage PSU has two similarly backlit meters with 12V bulbs fed directly
from a 6.3VAC winding. One or other seems to fail every few months. John.
[snip]