Look for a surplus transformer, you won't save any money trying to build one yourself.
That's a BIG supply to be using a linear regulator for, I suggest looking at some of the switcher IC's available now days, National Semiconductor makes a series called Simple Switchers which are FAR easier to work with than designing a switcher from scratch and they have HV versions which are good to 80V or so.
Wasn't that around the time the Dynaco ST-400 came out? I rebuilt one of those once, seems like it used a bunch of big Motorola power transistors, I forget the numbers but they weren't 3055's. Seems like there were 4 of each polarity per channel, or maybe it was 2, I do remember the heatsinks were HUGE.
In message , dated Wed, 9 Aug 2006, James Sweet writes
Many manufacturers used 'custom' devices which were allegedly tested to custom specifications by the device manufacturer. The Vcc max might be higher than for the normal device, and/or beta range might be less.
-- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk 2006 is YMMVI- Your mileage may vary immensely. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
"James Sweet"
** 1973, according to this schematic:....... Phil
In message , dated Wed, 9 Aug 2006, Phil Allison writes
38494 is a custom part number, but 40411 looks like a standard part. What substitute devices are used for repairs?My 303 suffered its second elco failure recently, and an elco in the 33 preamp came out in sympathy. Coincidence. Of course, I put new elcos in both channels.
-- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk 2006 is YMMVI- Your mileage may vary immensely. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
I've replaced 40411s with 2N3773.
Graham
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.
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
u know ...if u really wish to "learn" ...why dont you design yourself a
50A, 0-50V continuously variable SMPS ....capable of operating in both CV and CC modes.(i know what some ppl are going to say ....he wants to learn ...not repent)
I have a HP 6268B here with a bad transformer. I didn't even think of rebuilding the transformer. Well it did do 0-40 volts at 0-30 amps. I just recently got the idea to buy another used transformer at some reduce specs to install in the beast. Hmmmm.
greg
Given the replies i've had on this, it seems the more sensible way of going about it. Whilst i'm sure I will enjoy with experimenting with transformers in the future, building a power transformer - specifically the beast i'm after does seem to be costly and time consuming going by the responses i've had on this thread, and is unlikely to work (first time around anyway), where in contrast I could just pick up old/broken equipment at the local car boot sale for under a fiver. I've had a little read on (very basic concepts of) switching mode power supplies, and this does seem to way to go in terms of efficiency and size.
So yes, forgive me for my sins, I repent! ;)
Thanks to all those that offered their advice however, it's been insightful to me, and I certainly wont give up the opportunity to build my own transformers in future... just not on such a power crazed level where there are better solutions.
Regards, Mark
Also realize 50A at 50V is 2500 watts at 100% efficiency. If you are in the USA, you will need a 220V power connection to do this.
David
--------------8 So yes, forgive me for my sins, I repent! ;)
Wow, pretty sure i'm not going to need 50A at any voltage... not sure where that came from as originally I only wanted 10A. Incidently though, im in the UK so we have 230V by default.
All Pro-Electron numbered devices beginning with "A" are Germanium!
Not to mention the heatsinks it'll take when you want to deliver, say,
12 volts at anywhere near that 50 Amps. Hint: Plan on a fan and wheels.Isaac
I'd also query the need for such a large bench top supply - unless you're regularly repairing or building things like power amps.
--
*The man who fell into an upholstery machine is fully recovered*
Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
aha, you've discovered one of my planned future hobbies :) any money in it though?
In message , dated Fri, 11 Aug
2006, Mark Fortune writes
Yes, you'll spend quite a bit.
Everybody and his dog makes power amplifiers. Try something else (which is small-signal and thus less likely to emit flames and smoke). For example, low-level active crossovers; 2-way, 3-way, 4-way, Butterworth, Linkwitz-Riley, Bessel, transitional Gaussian, Thiele....
Enough to keep you busy for 50 years. And there isn't a great deal of competition, at sensible prices, so you could sell a few on Ebay. There is other low-level stuff which, compared with power amps, is a doddle to get working if you master the design mathematics.
And you only need a +/- 12 V power supply at 10 mA. (;-)
-- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk 2006 is YMMVI- Your mileage may vary immensely. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
Is there REALLY a market for active crossovers?
...Jim Thompson
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