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Old 10th July 2012, 07:28 AM   #11
CBS240 is offline CBS240  United States
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Is the toroid sealed? If it is not, you can add more windings. Just use the same ga magnet wire as the secondary winding already there. Remove the outer insulation exposing the secondary winding. (the primary should be seperately insulated from the secondary inside) Wrap a few turns of wire around the core and measure the unloaded voltage. Then load the winding with a resistor and measure the voltage, ~1A or so. Divide by the # of turns and this will give you approximate V/turn. Add two seperate 10VAC windings so that each one covers the entire area of the core and place them in series with the ones already there so that you get 35-0-35VAC. This is one reason I like the toroid kits, easy to manipulate. That and the fact they are cheaper.
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Last edited by CBS240; 10th July 2012 at 07:32 AM.
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Old 10th July 2012, 08:18 AM   #12
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Originally Posted by CBS240 View Post
Is the toroid sealed? If it is not, you can add more windings. Just use the same ga magnet wire as the secondary winding already there. Remove the outer insulation exposing the secondary winding. (the primary should be seperately insulated from the secondary inside) Wrap a few turns of wire around the core and measure the unloaded voltage. Then load the winding with a resistor and measure the voltage, ~1A or so. Divide by the # of turns and this will give you approximate V/turn. Add two seperate 10VAC windings so that each one covers the entire area of the core and place them in series with the ones already there so that you get 35-0-35VAC. This is one reason I like the toroid kits, easy to manipulate. That and the fact they are cheaper.
i will say this is a unwise dangerous thing to suggest for someone who don't have a lot of experience! it is not just this and just that. is nothing just about rewind a transformer!
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Old 10th July 2012, 08:29 AM   #13
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if your transformers are 300VA+ they will be great for F5 turbo V2, so selling them will not be a problem.
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Old 10th July 2012, 02:30 PM   #14
CBS240 is offline CBS240  United States
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No more dangerous than handling filter caps with 100VDC. If you must use this transformer, it is a fairly simple task to add extra secondaries onto a large toroid, assuming it is not glued together, everything is on the outside, (under the outer polypropelyne tape insulation) no rewinding required. Just wrap two separate 10VAC windings in a bi-fillar manner on top of the existing secondary so they completely surround the toroid and connect each one in series to each end of the existing secondary(s), solder splice with heat shrink tubing. Then re-apply the outer polypropylene tape insulation. The primary and mains connections and the secondary that is already there would not be manipulated in any way. Of course, always check for electrical insulation between primary and seconday. I suppose a complete novice might not want to do this, but if you can properly assemble a stereo kit into an enclosure, this task ought to be fairly easy. If the transformer is too small, then you will certainly have to buy another one. For 240W of output power you would probably want something about 500VA. The expense of buying the wrong transformer can be a good lesson in learning to calculate the proper transformer size/voltage before you buy it. If you can get a refund, sell it, or use it for another project, that would be the easiest solution.
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Old 10th July 2012, 03:42 PM   #15
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then teare apart some 100V caps and re-build them and put 100V on them.
and pop a 100cap is less dangrous then having a transformer burn down the house do to bad insulation. or electric shock.
and if it works. it's a good chance the transformer windings will vibrate as hell.
not wourth for saving 10-20$ if you ask me.
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