Cambridge Audio A500 Amplifier problems!

[camallison]

You're probably aware that toroidal transformers can have a large inrush current on power up.
Colin

No, that fact I didn't know. Presumably, you're comparing that to the in-rush current for a conventional transformer of the same VA rating. Why is that current so much larger for a toroid - and do you have any idea of the ratio of those two currents?

Just curious - and keen to learn.
Thank you.

Al. / June 5 //

Yes, compared to a conventional transformer. Why? I don't know, but it was something I learned the hard way, with a product recall on industrial control equipment of the 30 to 50 VA rating. I will consult one of my learned engineering buddies who was involved at the time and ask the question.

Colin

PS - while waiting for his reply, I found this:

"When fitting a toroidal transformer, it is important to avoid making an unintentional short-circuit through the core (e.g. by carelessly fitting a steel mounting bolt through the middle and fastening it to metalwork at both ends). This would cause a large current to flow through the bolt, converting all of the mains input power into heat, and blowing the input fuse. To avoid this, only one end of the mounting bolt must be fixed to the surrounding metalwork."