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Primrose(SumR Audio) Toroid GB

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buzzforb

buzzforb

Member
Joined 2010
Here is Richards reply.

"Everyone received mounting hardware, except for the transformers with epoxied centres.
Mounting hardware was placed on top of the packaging, so they were seen on opening the box.
Shipping / postage could move their location in the box.

ALL “800VA” and 1000VA have a epoxied centre with 3/8” drill hole.
Metal washer and neoprene pads are not required with a potted centre.

Every member of your group received a packing slip which reads as follows:
“do not allow your mounting bolt to touch grounded metal surface above the transformer. This includes the chassis cover.”

Bolt length becomes custom to the cabinet size a member has chosen.
Make sure the bolt length you choose for your project does not touch the chassis cover above the transformer. A short turn can result.

Richard"
Click to expand...

From this I gather the following. The mounting hardware(pads and plate) are included on non epoxied transformers. the bolt is not included, as its length is determined by the application.
 
L

Lo_Tse

Member
Joined 2006
Buzz,

Thank you for relating the information so quickly. I ordered 2 x 800 VA trafos and they do come with epoxied center (I was wondering about that since I did not order that). So no mounting gear come with them. It is all clear now.

I did read the information that Richard placed in the box (which was exactly what you posted). But I do not understand how the bolt, if touching the chasis cover, will short out the trafos. Also, the bolt will be in contact with the bottom of the chasis (to lock the trafo in place) and that's OK?

I'll be grateful if someone cares to enlighten me :eek:.

Regards,
 
P

petefrontiers

Member
Joined 2010
Lo_Tse said:
Buzz,

Thank you for relating the information so quickly. I ordered 2 x 800 VA trafos and they do come with epoxied center (I was wondering about that since I did not order that). So no mounting gear come with them. It is all clear now.

I did read the information that Richard placed in the box (which was exactly what you posted). But I do not understand how the bolt, if touching the chasis cover, will short out the trafos. Also, the bolt will be in contact with the bottom of the chasis (to lock the trafo in place) and that's OK?

I'll be grateful if someone cares to enlighten me :eek:.

Regards,
Click to expand...

The epoxied center and the bottom rubber pad isolate your transfo from the case and the mounting bolt. It is ok.
 
R

Russellc

Member
Joined 2003
Paid Member
I guess I am unclear....no bolt B/C he cant determine what? If it cant touch the top (and why you would want it to is beyond me) then its just a bolt long enough to go through the transformer and bottom plate right?

Similarly it sounds unwise not to nestle it on top of a rubber washer like Antek does, no? Obviously I am misunderstanding? I have only bought transformers from Antek previous to this, they all came with rubber washers and a bolt...which was good on the length EVERY time. Please clarify, I mean it is what it is and all but what?:confused::confused::confused::confused:

Russellc
 
L

Lo_Tse

Member
Joined 2006
buzzforb said:
Bolt through one grounded plane is ok, but if you have the bolt running through a grounded piece of metal on top and bottom, you have created magnetic pole.
Click to expand...

Buzz,

Thank you for the explanation. Although I still do not quite get the picture, I tend to agree with you that it has something to do with magnetic induction and not electrically related. The bolt is not conencted to anything that has voltage, therefore there is no current flowing through it. Anyway, I think I will put a rubber pad under the trafo when bolt it onto the bottom plate of the chasis. This should help to reduce any movement of the trafo.

Regards,
 
F

Flodstroem

Member
Joined 2004
Lo_Tse said:
Buzz,

Thank you for the explanation. Although I still do not quite get the picture, I tend to agree with you that it has something to do with magnetic induction and not electrically related. The bolt is not conencted to anything that has voltage, therefore there is no current flowing through it. Anyway, I think I will put a rubber pad under the trafo when bolt it onto the bottom plate of the chasis. This should help to reduce any movement of the trafo.

Regards,
Click to expand...

yes you are absolutely right about the magnetic induction:
If you have the trough bolt connected to a ground plane (eg. a chassis part) on both sides of a toroidal transformer the bolt and chassis create a short turn on the transformer making fuses (primary) to blow or if not, you will heat up the bolt to a melting temperature.
The effect will be the same as if you wound one turn of magnetic wire on the toroidal transformer and then short it.

If there is a chassis where you have to place the bolt trough the chassis on both sides of the toroidal transformer, then you have to isolate one side of the bolt (for example by PCB-laminate and PVC-tubing) then there is no risk for a short circuit. Best strategy is to isolate both sides of the mounting bolt. ;)
 
buzzforb

buzzforb

Member
Joined 2010
Little update. Transformers arrived Friday, the 26th of last month. Unfortunately I was out of town all week and this was unexpected, so I only got a couple shipped that Saturday. I will be leaving town again this Monday and will be gone through Wednesday. Friday I go on family vacation. It is my hope that on Thursday before leaving, I will be able to ship about half the transformers. May be more, may be less. Depends on regular job. Otherwise, shipping will commence when i get back.
 
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