[Tubesforme]

Aha! Yep, that's different. Still means you have some leakage between Chassis and primary but not a short necessarily.
Open winding does not cause this, but the reason for the open winding and the leakage could possibly be the same.
Like corrosion. As it takes quite a wallop to open 2.5V winding due to over current.

Thanks, I had written circuit breaker when I met GFI and only caught the error once I had posted it so left it alone. I totally agree with you. I only asked the question to see if anyone had the same ideas I had. I believe any transformer of this age might easily have some leakage and corrosion. However the replacement transformer has solved my problem.