Building a transformer
in [Design]
|
Prev: Texas Instruments microcontroller
Next: potentiometer
From: Eeyore on 9 Aug 2006 04:58 John Woodgate wrote: > In message <4jtfg7F9hi9fU1(a)individual.net>, dated Wed, 9 Aug 2006, Phil > Allison <philallison(a)tpg.com.au> writes > > >RCA 38494 and 40411 used in the famous Quad 303 hi-fi amplifier. > > 38494 is a custom part number, but 40411 looks like a standard part. > What substitute devices are used for repairs? I've replaced 40411s with 2N3773. Graham
From: Tim Shoppa on 9 Aug 2006 06:10 Lostgallifreyan wrote: > By a lot of cheap toroidals on eBay, 5A at some low voltage that doesn't > sell well. I have to agree with the sentiment 100%. Surplus transformers are always going to be cheaper than custom-built :-). Most oddball transformers on E-bay sell for pennies on the dollar (actually most don't sell at all!) And construction and mounting-wise, a lot of small transformers are way easier to deal with than one mammoth one. Above a very small number of VA you start building the case and mounting reinforcements around the transformer anyway :-). Tim.
From: Adrian Tuddenham on 9 Aug 2006 06:42 Mark Fortune <mark(a)fortrex.co.uk> wrote: > I think what you're saying is "try learning on some smaller transformers > first" I might just do that, cos it'd be a PITA if I screw up on a big > one and have to unwind it all again :] Very small transformers have large numbers of turns and the wire is thinner. Somewhere around 50 to 100 VA is a good size to learn on. If you can get a split bobbin, you will avoid a lot of safety issues. For winding heavy wire, I find it best (in the absence of a large enough winding machine) to tie one end of the wire to the front gatepost, then lay it down the side of the house and down the back garden path. I walk up the garden, reeling-in the wire onto the bobbin and counting the turns as I go. The tension is easy to control by just keeping a steady pull against the wire. Carry tools, string, insulation material and adhesive tape in your pockets; you won't be able to put the core down to go and fetch them because the windings will spring undone. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
From: isw on 9 Aug 2006 23:26 In article <44d8d62e$0$26602$da0feed9(a)news.zen.co.uk>, Mark Fortune <mark(a)fortrex.co.uk> wrote: > Greetings to the collective. > > For my next project I want to build a bench power supply and do away > with this old switch mode AT computer PSU that i'm currently using. > > The design I have in mind will be pretty beefy, giving a wide range of > fixed and variable output voltages (i'm thinking from -50v up to +50) > and deliver up to 5amps of current. if my estimates are right i'll need > a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've > had a look at some transformers in this range, and they're a little out > of my price range. so now i'm considering building my own. > > The specifications I need are as follows: > > primary: 0-230v @ 50Hz > Secondary: 60v-0-60v > secondary output current max: 5A > > I have an intermediate understanding of transformers, but have never > actually built one, hence I am seeking advice from those with experience > in this field. > So where do I start? what type of core is best for this application? - I > have a friend who's blasting off that toroids are best, but i'd like a > second opinion, and what kind of wire to use for the primary and > secondaries? what are good safety practices regarding insulation? Is > this even a feasable project to undertake (moreso on the money side than > timewise). Any other advice also greatly appreciated. Look for a blown-out 200-400 watt audio amplifier (or receiver) at a garage sale. The transformer you'll find in it will be pretty close to what you want. The amp will also include a lot of other very useful items such as big heat sinks, and so on. Isaac
From: sparc on 10 Aug 2006 14:59
2N3055s ...and AD149s ... all Si too ... |