UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

boiss · 22nd Oct 2006, 10:10 am

OK, I have looked at this 300VA tranny and the tpv is approx 3, ie. with ten turns wound on the output was 3.24V. I was wrong about the secondary, it's not quadrifilar but sextofilar with wire around 0.8mm dia. The DC resistance of the primary is 4 Ohms. After doing some tests with a series resistor on the primary, I found that the inductance of the transformer off load is of the order of 73H, this would appear to be a pretty good ballpark figure for an Audio O/P transformer. The resistance is also very low at 4 Ohms.
Each turn on the toroid would be a tad under 8" so if a 12" long shuttle was used it would only need a third of the total number of turns on it.
As for the windings, if two separate primary windings are put on the toroid with each occupying only 180 degrees of the toroid they will be more matched than by putting one on top of the other.
Any suggestions?
Mike.

22nd Oct 2006, 10:10 am	#16
boiss Pentode Join Date: Jun 2006 Location: Malaga, Spain. Posts: 235	Re: Toroids as O/P trannies OK, I have looked at this 300VA tranny and the tpv is approx 3, ie. with ten turns wound on the output was 3.24V. I was wrong about the secondary, it's not quadrifilar but sextofilar with wire around 0.8mm dia. The DC resistance of the primary is 4 Ohms. After doing some tests with a series resistor on the primary, I found that the inductance of the transformer off load is of the order of 73H, this would appear to be a pretty good ballpark figure for an Audio O/P transformer. The resistance is also very low at 4 Ohms. Each turn on the toroid would be a tad under 8" so if a 12" long shuttle was used it would only need a third of the total number of turns on it. As for the windings, if two separate primary windings are put on the toroid with each occupying only 180 degrees of the toroid they will be more matched than by putting one on top of the other. Any suggestions? Mike.