It turned out that the enclosure I picked wasn't as high as I thought when ordering it. So now I've an interesting issue with mounting the toroids. They fit perfectly on their own. However when stacked with the rubber pads and the top bracket, they are the exact height of the case. It closes but the metal bracket touches the top of the case.
I was trying to find a more detailed explanation about toroidals and the shortened loop effect, but I wasn't too successful. What is it that I should avoid exactly? If the bracket and the chasis are insulated with something in between, isn't that going to be enough to prevent problems? I don't want to close the lid and discover that things are going to explode.
I was trying to find a more detailed explanation about toroidals and the shortened loop effect, but I wasn't too successful. What is it that I should avoid exactly? If the bracket and the chasis are insulated with something in between, isn't that going to be enough to prevent problems? I don't want to close the lid and discover that things are going to explode.
Pour a bit of epoxy into the toroid (about half full) then drill a hole in the centre and use a much shorter bold. Now there is no chance for the bolthead to touch the cover.
The rubber disc under the transformer is to insulate mechanical vibration.
If the cabinet is steel you may find a bit of mechanical hum coming from the cover but electrically it should not be a problem.
The rubber disc under the transformer is to insulate mechanical vibration.
If the cabinet is steel you may find a bit of mechanical hum coming from the cover but electrically it should not be a problem.
As long as the transformers have the Rubber pads before the metal wash(top/bottom),everything is fine.bare wires from transformers should never touch the metal chassis(just in case of the coating of wire from transformer peels off and touch the metal chassis).Always isolate transformers from chassis (if it is metal).if you check with an ohmmeter you will see that the bolt and metal bracket touch the chassis but, the bolt and metal bracket DOES NOT touch the wires of transformer because of the rubber pads.
The epoxy is a really nice idea. I've seen toroids with center screws, that'll probably work out perfect.
There are some ventilation holes as well, I could try to use them and secure the toroids with cable ties, that should probably work out nicely as well.
Good thing you reminded me to leave an extra layer of insulation between the trafo and the chasis, it's always a good idea to keep things insulated better.
There are some ventilation holes as well, I could try to use them and secure the toroids with cable ties, that should probably work out nicely as well.
Good thing you reminded me to leave an extra layer of insulation between the trafo and the chasis, it's always a good idea to keep things insulated better.
That reminds me that I was wondering about something else. I've a small circuit made on a prototyping board - inrush current limiting. The problem there is that the bottom side of the board is covered with uninsulated tracks. Any ideas what I could use to coat them with, so I can be sure nothing would accidentally touch the board and short something, or bring potential to the chasis?
Of course, the chasis will be connected to safety earth and there are fuses as well, but I don't want to leave any chance for mistakes.
Of course, the chasis will be connected to safety earth and there are fuses as well, but I don't want to leave any chance for mistakes.
Atilla said:
That's shorted. This is where a part of the metal structure of the box or transformer mount forms a complete conducting loop that passes through the hole in the toroid as it would if for example you used Jubilee Clips (metal hose clamps) instead of cable ties to secure the TX to the chassis. The same thing can happen if a securing bolt touches both the top and bottom of the enclosing box. It then becomes a secondary winding.
For mounting PCBs you can use a standoff. You can get self-adhesive ones, they have a harpoon like spring clip that passes thru a circular hole in the PCB and then latches open.
w
Sorry - shorted, of course. I read it wrong and then started wondering ... what on earth is a shortened loop. *sigh*
Conductive material around the toroid core, no load - bad situation. Thanks for getting my brain working right again.
Conductive material around the toroid core, no load - bad situation. Thanks for getting my brain working right again.
You can use "double side stick tape" for your inrush current limiting board or use "five" drops of silicone one in each corner and one in the middle.
Atilla,
the inrush limiter is in mains potential so I wouldn't risk
i would spray the exposed tracks with paint or lacquer (stops the copper from oxidizing as well)
use standoffs too to secure the thing in place ~
http://uk.farnell.com/ettinger/05-02-123/spacer-m2-5x12-ni/dp/1466771
good luck!
Evan
the inrush limiter is in mains potential so I wouldn't risk
i would spray the exposed tracks with paint or lacquer (stops the copper from oxidizing as well)
use standoffs too to secure the thing in place ~
http://uk.farnell.com/ettinger/05-02-123/spacer-m2-5x12-ni/dp/1466771
good luck!
Evan
They're tin plated, so oxidising is not an issue (it's not, right?) but yes, I was thinking of some sort of lacquer, prefferably something that will sustain heat and won't catch fire. It's just that I haven't really used that sort of things.
you can use small rings over the bolts and between topplate and/of bottom plate and the sidewalls. In this way you win a few millimeters and you create a better ventilation
I've managed to solve the toroid mounting issue nicely.
I got a silicone glue gun, some epoxy and a few small tubes, used in plumbing, just slightly larger than the 5mm bolts I'll use.
I put a small piece of nylon, one of the baggies for electronic components on the ground and the toroid on top of it. I positioned the tiny pipes in the center of the toroid hole, filled the bottom with a layer of melted glue, so no epoxy would leak. Then I filled the inside with epoxy, up to the level where the small pipe ends. Left to dry, removed the nylon on the bottom (silicone won't stick it there permanently) and voila! Now the locking nut goes inside the center hole of the toroid and it doesn't have to stick on top, where it is a problem. The pipe in the center helps with two things - I don't have to drill the epoxy afterwards and it strenghtens the construction by taking all the force that would be vertically applied on this thing. It's pretty neat and very stable.
Now I've another small dilemma - the top and bottom covers of my case have holes in them for ventilation. I can turn those either way, which is convenient. I was thinking to leave the bottom holes in the "back" of the case, where the chips would be and the top holes in the "front" where the toroids are. This way the air would move all the way trough the case and cool everything a bit. However, I'm not sure it's really worth it at all, since the heatsinks are external and that is where the chips cool off. Furthermore - the toroids really don't seem to get hot at all, they're a pair of 120VA each. Maybe I should just leave the holes on the one side and have them move as much air around the chips to keep the ambient temp around them down?
I got a silicone glue gun, some epoxy and a few small tubes, used in plumbing, just slightly larger than the 5mm bolts I'll use.
I put a small piece of nylon, one of the baggies for electronic components on the ground and the toroid on top of it. I positioned the tiny pipes in the center of the toroid hole, filled the bottom with a layer of melted glue, so no epoxy would leak. Then I filled the inside with epoxy, up to the level where the small pipe ends. Left to dry, removed the nylon on the bottom (silicone won't stick it there permanently) and voila! Now the locking nut goes inside the center hole of the toroid and it doesn't have to stick on top, where it is a problem. The pipe in the center helps with two things - I don't have to drill the epoxy afterwards and it strenghtens the construction by taking all the force that would be vertically applied on this thing. It's pretty neat and very stable.
Now I've another small dilemma - the top and bottom covers of my case have holes in them for ventilation. I can turn those either way, which is convenient. I was thinking to leave the bottom holes in the "back" of the case, where the chips would be and the top holes in the "front" where the toroids are. This way the air would move all the way trough the case and cool everything a bit. However, I'm not sure it's really worth it at all, since the heatsinks are external and that is where the chips cool off. Furthermore - the toroids really don't seem to get hot at all, they're a pair of 120VA each. Maybe I should just leave the holes on the one side and have them move as much air around the chips to keep the ambient temp around them down?
Sure. Here's what I mean.
I've got this panel, with the openings on the rear side of it:
Say that the chips are mounted close to it like so:
So, I was thinking, should I keep those openings in the rear side of the case, one on top of each other, or reverse the top one, and have the opening on the front side of the case, so the air has to pass through the whole case? I'm not sure there's any gains one way or the other.
I've got this panel, with the openings on the rear side of it:
An externally hosted image should be here but it was not working when we last tested it.
Say that the chips are mounted close to it like so:
An externally hosted image should be here but it was not working when we last tested it.
So, I was thinking, should I keep those openings in the rear side of the case, one on top of each other, or reverse the top one, and have the opening on the front side of the case, so the air has to pass through the whole case? I'm not sure there's any gains one way or the other.
BTW, trafo with epoxy filling:
I seriously need a decent camera, this Nokia is creeping me out. 🙂
An externally hosted image should be here but it was not working when we last tested it.
I seriously need a decent camera, this Nokia is creeping me out. 🙂
Hi Atilla,
the case is an HIFI2000 one, isn't it? 😉
If so I don't think you can reverse holes because of the bent that closes the back aluminum sheet:
I've arranged mine in this way:
Don't worry about ventilation, the amp is cold (using case's dissipating panels).
the case is an HIFI2000 one, isn't it? 😉
If so I don't think you can reverse holes because of the bent that closes the back aluminum sheet:
An externally hosted image should be here but it was not working when we last tested it.
I've arranged mine in this way:
An externally hosted image should be here but it was not working when we last tested it.
Don't worry about ventilation, the amp is cold (using case's dissipating panels).
Actually this is sold by Elfa, marked as an "Instrument case DS 2480", manifacturer "Teko". But it looks exactly as the HIFI2000 products. To the last detail.
Well to be fair, I could reverse the panels, but then the edge would show in the front as well and wouldn't be so nice. I'll give it a careful look.
BTW - where are those R-cores from? They seem to be a much easier fit in this box 🙂
Well to be fair, I could reverse the panels, but then the edge would show in the front as well and wouldn't be so nice. I'll give it a careful look.
BTW - where are those R-cores from? They seem to be a much easier fit in this box 🙂
Atilla said:
I've buyed them from France, Selectronic
To me seems that your case is the 'slim' version (40mm high), mine is 80mm high and transformers are 55mm high.
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