Hey guys,

This is a bit of a noob question, but here goes...

I'm building some audio gear and mounting it into a chassis. It uses a toroidal mains transformer. I am wondering the best way to mount it in the chassis without drilling a hole in the chassis and having a big nut on the outside of the case...

Thanks.

 

Thread the inner epoxy ring of the transformer. Then you can either weld a threaded stud onto the chassis, or pass a machine screw through a drilled hole (tidier than a nut) and screw the transformer onto either one. The advantage to the mount is that the transformer doesn't come loose when somebody drops the amp and trash the innards.

 

aha... good idea. Thanks for the tip!

 

Beenthere, I can't picture what you've written.

Attempting to thread a toroidal transformer could lead to severe problems, the least of which might be degrading the efficiency of the transformer, the worst may be creating an unintended path for mains voltage to the chassis if a mains winding may be nicked.

I suggest that instead of modifying the mains toroidal transformer in any way, that three "U" shaped insulated brackets be expoxied to the chassis on the same radius of the toroidal transformer, spaced 120° apart, using something like J-B Weld, and that Zip-ties (nylon locking ties) be used to secure the toroidal transformer to the brackets.

The nylon Zip-ties will not interfere with the electrical characteristics of the toroidal transformer. If ferrous metals were introduced into the equation (particularly in the middle of the toroid), the characteristics of the transformer would change.

 

ahh ok. thanks. If i'm going to do that, couldn't i just mount it with regular hardware (a bolt and plate) and jb-weld the other side of the bolt to the chassis? Seems like that would be easier.

 

Really, I don't have enough information.

Do you have an image of the transformer that you could post?

If the bolt were ferrous and were to pass through the middle of the transformer, I would say no. That would change the electrical characteristics of the transformer in an unpredictable manner. If the bolt were made of nylon or other non-ferrous material, then it would be OK.

Of course, you could just epoxy the transformer directly to the chassis. That might make replacement a bear, but you wouldn't change it's electrical characteristics.

 

I'm thinking of using something similar to this:

http://fivefishstudios.com/index.php?option=com_content&task=view&id=47&Itemid=64

I've used that exact tranny with that mounting hardware (which came with the actual transformer, from what i understand) on another project and it posed no problems. The problem is: i don't like the big ugly bolt on the bottom of the chassis.

From what i've read, as long as the transformer/bolt/hardware doesnt make contact to both top and bottom of the chassis (creating an extra shorted winding) then i should be ok. This may or may not be 100% accurate... just what i've read

Of course, you could just epoxy the transformer directly to the chassis. That might make replacement a bear, but you wouldn't change it's electrical characteristics.

Yeah thats an option... however, i am hesitant because i'd like to be able to rotate the transformer if necessary to reduce hum in the signal.

 

Before you get too worked up, check out the AMVECO line of toroidal transformers in the Digi catalog. They come with an epoxy plug in the center that clears a #4 metric bolt, or takes a 12-24 thread (little tight, but epoxy doesn't gall).

The advantages to toroidal core transformers is that all the flux is confined to the core. The bolt in the middle is supposed to be there for mounting. I just fudge by cutting threads for SAE hardware.

 

Before you get too worked up, check out the AMVECO line of toroidal transformers in the Digi catalog. They come with an epoxy plug in the center that clears a #4 metric bolt, or takes a 12-24 thread (little tight, but epoxy doesn't gall).

Yeah for this project i actually am using an amveco. Although, now that i think about it, is there any real advantage to threading the core? Might as well just use a bolt, right?

 

I do because it is better for my purposes. If you use a flat washer and lock washer so the hardware stays tight, there's no advantage in threading the core plug.