Toroidal transformers mounting

[akis]

Hello

For my guitar amp projects I have two toroidal transformers. I seem to remember that you must not earth the bolt that holds the toroidal in place because it passes through its centre. Are there any other restrictions? Could I mount two toroidals one on top of another? Or must I keep them a certain distance apart? How about other boards? Can they be close to the toroidals or do I have to observe some minimum distance?

Thanks

[Spiny]

The bolt may be earthed - the important thing is that the bolt / chassis/ top do not make a complete circuit - this is the same as a single shorted turn and will blow the fuse if your lucky.

You can stack torroids but its best not to due to ventilation considerations.

Depends on the board. Input boards keep away, PSU boards not a problem.

[TroelsM]

Hi.

The bolt may be connected to earth via the chassis, but it is bad idea to connect anything to the transformer-bolt.


The internal Gnd-wire from the mains-plug (or the PSU) should always be connected to the chassis using a seperate bolt, and not the transformer-bolt.

That my understanding anyways.

Kind Regards TroelsM

[akis]

Originally Posted by Spiny

The bolt may be earthed - the important thing is that the bolt / chassis/ top do not make a complete circuit - this is the same as a single shorted turn and will blow the fuse if your lucky.

You can stack torroids but its best not to due to ventilation considerations.

Depends on the board. Input boards keep away, PSU boards not a problem.

That's how I figured it as well, keep low level signals as far as possible.

But I do not understand "do not make a complete circuit" ? Circuit with what? If the bolt is part of the chassis, and therefore at ground level, that is all there is to it. I am confused

[Atilla]

As in - do not make an electrically conductive loop around the core of the transformer, in any way. It'll be like winding a single-turn secondary and shorting it, which you can imagine to be a very bad thing indeed for your transformer.

[AndrewT]

If the lid of the metal enclosure is flexible then leaning on it may allow the bolt to touch the lid while the other end is in contact with the bottom of the chassis.
This would be a shorted turn and very quickly damage your transformer while you are trying to work out why you are hearing excessive hum and buzzing coming from the box and the speaker.

Two to four layers of robust insulation between the bolt and the lid help avoid this type of accident.

[akis]

Things I would never think of Anyway it is going inside a wooden box...