[johnyjf]

The hum is quite loud, certainly more than I am prepared to live with in an oil filled transformer. Its about as noisy as a small battery power drill. I do have a Variac somewhere and I will hook that up to it with my Avo to measure the AC current. Will try it this afternoon. To be honest even if it is not a fault I'm not prepared to use it if it makes that level of noise. Will let you now how I get on. Thanks for the responses.