transformers in parallel

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Probably just as well you lost that bid. It would have been a very cumbersome and inefficient way to get the power supply you need on the cheap. But if you really want to do it that way, I'll give you a full flat rate box of transformers equivalent to Signal 241-6-16, which are 16 VCT at

2A. Just send me $10 by PayPal and I'll send you as many as will fit in the box. I have at least 100 pieces surplus. They are a little rusty but work fine. You can hook them up FWCT and get about 10-12 VDC at 2A from each, and you can add them up in series to get any voltage you want. I'll also throw in a bag of 100 1N4004 diodes. Same offer for anyone else. I need to get rid of them, along with about 1/2 ton of other parts. Some are listed on
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But I still wonder why you are trying so many different approaches. I gave you links to some good deals on transformers and switching supplies. Why don't you buy one of these switching supplies from this guy:

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He also has some audio amp ICs, PCBs for same, and other cool stuff.

You should have been at the HamFest in Timonium this past weekend. Some of the vendors had nice switching supplies, linear supplies, and transformers that would work for your needs, for only a few dollars, and trash cans full of freebies that were being hauled to the dump with a front end loader. It's a shame what gets thrown out, but the expense to advertise on eBay and then ship especially heavy stuff is just prohibitive. And now it costs a lot for these guys to load down their vans and drive 100-200 miles to sell $50 of stuff in a day.

Two years ago I bought a 5 HP motor-generator set designed to teach motor fundamantals, and they can be wired in various ways. They were about 200 lb each, and I bought them for $30 each. If there is a HamFest near you, that's the place to go for bargains, and also to meet other people who have solid experience and/or wild and crazy ideas. Find your most local one at:

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Paul

Reply to
Paul E. Schoen
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$10 by PayPal, shipping included in the price? Will think about it... 16VCT means two 8V, right? or 16+16=32?

guy:

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He also has some audio amp ICs, PCBs

Yes, I noticed one in particular - the 24V at, what, 8A or so, I forget... was a very good deal... shipping was kind of high though... then I noticed the eBay one...

Since I need -28-0-+28V, I'm wondering if two switchers, 0-24VDC, are NOT the way to go... some mentioned stability problems with two AT power supplies in series... which are underpowered, by the way (at least the ones I have, around 4A@12V)

Pretty much, since this is a hobby project, I'm going as cheap as I can make it. Otherwise, might as well just hop over to Circuit City and buy the factory-made deal... still have to visit the landfill, maybe there are some neat deals there... I never made a switcher before... the SG3525 sounds interesting.. the two Linear Technology chips you proposed sound kind of pricey...

Plus, I never like to build a circuit I've never seen before without understanding it, or getting feedback from experts. That's why I asked so many questions about the redcircuits.com amplifiers. Don't take it personally. ;-)

at:

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Thanks! I hadn't realized there was such waste...

Michael

Reply to
mrdarrett

guy:

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He also has some audio amp ICs, PCBs

at:

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Wow, May 18, Rancho Cordova? That's right in my backyard... thanks!

Reply to
mrdarrett

Yes, but the two windings are connected as a center tap, 8-0-8. They are virtually identical to the Hammond 187D16 described on

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I have some with dual primaries. I use them with a FWCT rectifier to get about 10-12 VDC (which I regulate to

5 VDC), and then I use voltage doublers to get +/- 25 VDC which I regulate to +/- 15 VDC. I don't need that much power, but I got a few hundred of these as surplus, and I had plenty of room. They are used in my Ortmaster product. See links in
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A FWB would give you about 20-24 VDC at 1 amp (maybe 1.5).

The eBay store I mentioned has a dual output switcher with +/- 43 VDC at 2 A, which is perfect for an amplifier that puts 100+ watts RMS into 8 ohms. It's about $30 including shipping.

Yes, you seem eager to learn and try things. Maybe because for most of these projects, I've already been there, done that, and I see no need to do things the hard way. I use LTSpice to try new ideas, and then unless I have a real need for the circuit, I just file it away for the future. I pretty much know it will work. But sometimes I like to breadboard things, just to make sure. There are usually surprises, especially with high frequency switchers like the one I recently designed and made PC boards. Layout is critical, and I expected about 92% efficiency, but could only get about

85%. And it's hard to make changes on a 1" x 2.5" board with mostly SMT components.
Reply to
Paul E. Schoen

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