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Re: [Amps] CD Cap

To: amps@contesting.com
Subject: Re: [Amps] CD Cap
From: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Reply-to: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Sat, 25 Mar 2006 18:25:04 +0000
List-post: <mailto:amps@contesting.com>
Rich wrote:
>
>Ian wrote: Have you told us everything that is printed on the capacitors
>
>themselves?
> Well I went back to CD web pages and did a little more digging. The 381
>type caps are high ripple and have a rating of 1.8 amps at 120 Hz. This
>should work for my P/S as I do not intend to load it very heavy.
>
For the DC current of a single 3-500Z you should be fine.... but to 
answer your original question, do leave some air circulating space 
between them.

>>This also brings up another question, I am going to use an old
>transformer. It has 230v input, three input terminals, out put is with
>terminals 1-2, 3000vac, with terminals 1-3 ,2090vac. Resistance is
>.45ohms
>input(1-2) or 1.02ohms input (1-3), output R is 41.4 ohms at terminal
>4-5.
>In another thread it was brought up about transformers for a choke input
>might be a problem?? How do I tell and why do I care? This is an old
>surplus transformer even to the point of having spark gap balls in
>parallel with the output terminals.

 From a quick run through the PSU Designer program, the 2090V AC 
connection with a full-wave bridge rectifier will give you about 2.6kV 
at 500mA, which looks OK for your single 3-500Z. (The tube could handle 
a little more, but the 3000V AC tap would be too high.)

>I intend to build this with a soft start relay set up.

Good idea, because 47uF is a lot of capacitance to charge up in the 
first few mains cycles.

It also implies a lot of stored energy that you don't ever want to dump 
into the tube, so don't forget the "glitch" (surge limiting ) resistor 
in the B+ line.


-- 
73 from Ian GM3SEK         'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek
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