On Wednesday, July 27, 2016 at 3:42:38 AM UTC-4, N_Cook wrote:

How to explore the internal solder of the hollow pins without disturbing
the join between bakelite and glass at the base?

Been doing this repair since 1978...

Touch a very hot iron to the pin, about midway between the point and the base. Hold for a few seconds. That should remelt the solder inside and reset the connection.

One of the few legitimate uses for a 200W soldering gun - be sure to pre-heat first. The idea is to get the pin hot enough to reflow the solder before the base knows what hit it. It is too little heat for too long a time that does damage.

Peter Wieck
Melrose Park, PA