[Arran]

Breaking the eye tube socket isn't really a concern unless the set has one of those awful Eby eye tube sockets with the solid Bakelite back. Most of the decent ones with a metal cover were made by Amphenol, opening those isn't too hard but you need a sharp flat bladed screwdriver to wedge into the slots on the cover, it's hard to break one unless you use excessive force. Most of the time when I need to open one up it's because the cable is shot and the wires need to be replaced. Some companies, like Sparton, had enough sense to install the 1 meg ohm resistor under the chassis rather then in the socket itself, the reason they burn out is because they used a 1/4 watt resistor where they should have used a 1/2 watt.
Regards
Arran