How do I mount big capacitors in a box?

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Hi there,

Well, here I am again, with my newbie questions.

I have a handfull of semi large capacitors (5 - 6 inches in height, just about one inch or so wide) that I'd really like to be mounted in my amplifier box in such way that they won't move around.

Are there any good "mounting kits" to buy, or do you guys (or gals) make your own mountings?

The parts dealers around here don't carry any such thing.


[Edited by swede on 10-10-2001 at 05:41 AM]
Havn't had any experience with this yet, but I have seen multiple people take two metal plates, and sandwich the caps in between, using four screws to tighten the plates together. They made a tab coming off of the plate at a 90 degree angle, so that it could be attached to the amplifier's chassis.
In one of my projects I chose to use 'double sided sticky pads' one can get almost from any office supply shop. I put the pads under every cap and also between the caps forming a unit of capacitors.... There have been no problems with such mounting. I have moved and transported the amp and this mounting doesn't seem to have problems with mechanical stress either. I think it's cost effective and good enough solution for personal use...
Are these computer grade with screws on one end or do they have wires out each end (axial)?
If they're computer grade, you'll find that they make aluminum clamps that screw to the chassis and tighten around the base of the cap. You may need to order them, but never fear, they're out there. Look in any commercially made gear and the bulk supply caps will be mounted this way.
If they're axial caps (or if you just want to lay computer grade caps on their sides for whatever reason) many people use silicone caulk--yes, the clear bathtub stuff--to glue them to the circuit board. It's a very good adhesive, cheap, and it absorbs vibration well. This is frequently done in even high-end equipment, particularly speaker crossovers.
Double-sided foam pads are a good short-term solution, but the adhesive will generally give out after about 5-10 years or so.

cap manufacturers usually also make mounting brackets for their large caps... what could be better than a purpose-built bracket? can use them to mount caps standing upright, or lying flat, depending on the bracket. If you can't find one from the manufacturer of your caps, other cap companies probably make them in the same diameter. These brackets are an inexpensive strip of metal, and should be a lot less work than many other options.
I am not too sure of the situation in other countries, but here in India it is surely easy to get things made even one-off. I have used stacks of 4 computer grade capacitors this way: make a mild steel enclosure, that fits the capacitors when they are laid out as a square. The top and bottom of the enclosure (with respect to the capacitors being upright) should be open. Make the height of the box, 1" more than the height of the capacitors. 1/2" of this extra length is flared out on one end to aid in mounting to the chassis, and the other 1/2" is folded inside to hold the outside edges of all capacitors in place. Such an enclosure can be mounted either horizontally or vertically. In either case, the top end of the capacitors go to the chassis end, with the flare helping to screw down things, the screws of the caps are left exposed via the opening where the folding is to the inside of the box. Bus bars can be fixed, making holes for the screws.

The above description would have been easier if I could post a drawing....

This would require the removal of the capacitor screws from the bus bars and a few more screws from the chassis/cap.enclosure to dismantle the entire capacitor assembly.
On the topic of capacitor mounting, look out for PCB mounted caps that are glued to the board. The glue is usually yellowish and can darken with age. Over time the glue often becomes conductive and/or corrosive. I have had to replace many in both professional and domestic equipment, look out for it!
I have not found this problem with hot melt.

Remember when mounting large caps with high ripple currents, give them room to cool. For every 10 degrees C the caps life is halved.

Regards WALKER
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