I noticed that the cable was falling out of my recently-acquired Radar 202 CRT tester adaptor box, so I thought it wise to restrain it with a cable tie internally before it pulls off a wire and I can't find where it came from!
Now, a long time ago I had one of these and I struggled to work out what the connections were as it was minus the adaptor box (ultimately this led to the tester being sold), so I took the opportunity to make a note of them for future reference, but also for those who wish to make custom adaptors e.g. for pre-war tubes, or more importantly the Mullard MW6-2. Or even just an octal plug to croc clips.
Connection from the CRT tester to the adaptor box is via an International Octal socket, and the connections are thus:
Pin 1 = Heater
Pin 2 = Heater
Pin 3 = n/c
Pin 4 = Cathode + A2 - this is on pentode tubes with the B12A base, connection is also made to pin 6 (marked i.c. in some books)
Pin 5 = Grid
Pin 6 = A3 - on the Radar this is a flying lead designed to connect to the final anode of the tube, and is a special 3-in-1 connector.
Pin 7 = A1
Pin 8 = n/c