Rich wrote:
>I have come across some new CD caps. 560 uF, 400Vdc, porm 20%, temp
>105C. 1.312 dia , 2.7 length , snap in.
>Looks like all plastic on the outside.
>
>Part number is 381561M400A072 , I can seem to find a spec sheet on them.
>12 will be going into a 3000/4000v power supply for one 3-500 type tube
>SSB amp.
>My question is, how much space do I have to have between each cap or can
>I box them together?
First question is: what is the ripple current rating? Don't commit
yourself to using them until you know.
The ripple current rating is about internal heating, which has a large
effect on capacitor life. For that reason you should always leave some
gap for cool air to circulate through the 4x3 stack, and then try to
make sure that air really does circulate.
There are many hot-spots in amps and power supplies where a small local
fan can have a big effect to reduce the heat stress on components.
Plastic 12V CD fans are easy to find from computer power supplies etc,
and are even available in sizes down to 1in square. Noise is not an
issue because of the main cooling fan.
Make cure that local cooling fans are close to the things you want to
cool, so the hot surfaces are well "scrubbed" by turbulent air. If the
fan is moved some distance away, the air flow is much smoother, so it
has much less cooling effect.
Regarding transformer cooling, I had good success with a 6in plastic fan
aimed directly at the transformer from a few inches away. Without it,
the smell of hot varnish had made the transformer unusable for long
weekend sessions. With the fan, no more problems.
--
73 from Ian GM3SEK
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