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Old 11th December 2012, 12:45 PM   #11
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
This the thread I was taking about:

Homebrew Toroidal Output Transformer
Osvaldo F. Zappacosta. Electronic Engineer UTN FRA from 2001.
Argentine Ham Radio LW1DSE since 1987.
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Old 11th December 2012, 01:48 PM   #12
madtecchy is offline madtecchy  England
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A quote arrived for toroids with only primarys...
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File Type: jpg toroid.JPG (40.6 KB, 208 views)
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Old 11th December 2012, 01:56 PM   #13
AndrewT is offline AndrewT  Scotland
Join Date: Jul 2004
Location: Scottish Borders
that makes sense.
The time to pick a single secondaryless item off the shelf and post it out only saves a fiver.
But to pick 10 from the shelf gets closer to the real saving.
I suspect by the time you get to 100 off one would get a much closer to real cost.
And it shows up the rip off merchants that charge more for a secondaryless transformer than the full article.

Why would there be primary only transformers on the shelf?
Because winding the primary/ies and insulating it is a separate operation and an operation that never changes. All the 300VA primary only are identical. Make a 1000 off or 10000 off and stack them until the secondaries are required for item stocking.
regards Andrew T.
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Old 11th December 2012, 06:29 PM   #14
Tarzan is offline Tarzan  Belgium
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Hi folks,

"ASK Jan First" (Ask Jan First ; electron tubes and more) has a new service.
They can provide you with custom made toroids trafo's, and others to, at very competitive prices.

I ordered one with the following secundaries:
15,75-0-15,75V, 400mA
32-0-32V, 5000mA
9.7V, 1200mA
250V, 12mA
11V, 950mA

It was for a Johnson Amp and the original had a short.

After 2 weeks It reached my door for a price of less then 140, shipping included.

Ask for a quote...
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Old 11th December 2012, 06:33 PM   #15
Tarzan is offline Tarzan  Belgium
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Here the direct links:

Custom made transformers with standard cores:
Netztrafos Einzelstcke

And toroids according to your specs:
Einzelstcke Trafos
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Old 11th December 2012, 10:35 PM   #16
rsavas is offline rsavas  Canada
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Location: Ontario
Plitron makes some nice ones, at a reasonable price, expensive to ship however. I find getting them with more than one secondary coil is a problem, you get into custom designs.
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Old 12th December 2012, 04:19 AM   #17
madtecchy is offline madtecchy  England
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Adding to the list .. Airlink transformers will give advice. Also provide a custom winding service.. UK based .

Last edited by madtecchy; 12th December 2012 at 04:25 AM. Reason: added link
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Old 12th December 2012, 06:53 AM   #18
Tarzan is offline Tarzan  Belgium
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Going back to the OP;
If it is for a one-off project (or even for 10 same amps) it's not worth the hassle to wind your own. You have to buy the cores, the wire, the insulation foil and so on.
Then you have to calculate the number of turns and find the correct toroid.
Not forget; wind them with the trouble involved.

To blow up the whole idea of doing it for cheap:
Spend a small fortunes on golden rca plugs, special audio grade caps, teflon or silver wire and a custom engraved front and back panel. Not to forget the sides of the amp made of an exotic hardwood with 15 layers of laquer, sanded in between with as much sheets of sandpaper.
As power tubes ( if a tube amp is build) the best power tubes are used for a steep price.
The search for the best sounding preamp tubes lead you probably (because they say so) to NOS tubes that cost a fortune.
Pots are changed by stepattenuators with golden contacts and 1% resistors.
And if it's solid state; Expensive FETS with a pcb stuffed with a box full of transistors and or IC's.

All the later cost so much that saving 20 or even 50 on a transformer is absurd.

You can also do it cheaper and build a common amp, be it sand or glass, and these transformers are available off the shelf.

If you're not in the field of winding transformers and especially toroids; I would suggest to try companies that will make them for you.

Anyway; I respect everybodies choice and it's allways up to the individual to decide.
And having finished you toroid and it works fine; it gives you a feeling of "It's alive! It's alive!"
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Old 12th April 2013, 03:08 AM   #19
gorgon53 is offline gorgon53  Finland
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if weigth is of no concern old variacs are excellent toroids and can sometimes be found cheap on ebay. In europ they have a 50Hz 260V single winding, so running them on 230V keeps them cool and quiet. Just make sure there are no overload signs on them (easy to see if some windings are daker than others). First clean off the carbon depost, then paint the whole thing with airdrying transformer paint. Isolate the primary properly, put electrostatic shield overlapping and over at least the full primary circumference without making any shorts (for better hf-shielding you may want to partition the schield and/or make multiple schields), wind the shield tape to halfway and then back a few turns so you can solder the shield connection (without burning the isolation), finish the remaining half, isolate again and now wind your secundaries (make sure to spread out each of the secundaries over the full circumference of the primary below).
Very high quality DIY toroidial transformers can be made that way.

Last edited by gorgon53; 12th April 2013 at 03:14 AM.
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Old 12th April 2013, 04:46 AM   #20
Redshift187 is offline Redshift187  Canada
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Antek has great prices and a great selection. I wish I'd found them before I ordered from Plitron.
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