I can't figure out this old transformer.

pinkphiloyd · 10th May 2011, 06:56 PM

No problem identifying the filament wires, rectifier wires, and HV out wires, but there are three primary wires. Black, black/red, and black/yellow. What's up with that and how do you wire it? Came out of an old organ. Only code on the trafo is C512-41.

sofaspud · 10th May 2011, 08:47 PM

Measure the resistance between each wire, and each wire and the frame and report the results.

BZed · 10th May 2011, 09:01 PM

What you have is a tapped primary. The black wire is the common connection. The black/red and black/yellow are the hot taps. Generally what these are used for is to give the transformer 115v and 125v taps. Measure the resistance from the black wire to the other 2. The one with the highest resistance will be the higher voltage tap. I would expect the resistance to be nearly the same for both taps, just a small difference.

Its possible that it could be a 120v / 240 volt setup. If the black wire to black/yellow reads 30 ohms for example and the black to black/red measures 60 ohms then the black/yellow is the 120v tap and the black/red is 240v.

BZ

10th May 2011, 06:56 PM	#1
pinkphiloyd diyAudio Member Join Date: Jun 2010	I can't figure out this old transformer. No problem identifying the filament wires, rectifier wires, and HV out wires, but there are three primary wires. Black, black/red, and black/yellow. What's up with that and how do you wire it? Came out of an old organ. Only code on the trafo is C512-41.

10th May 2011, 08:47 PM	#2
sofaspud diyAudio Member Join Date: Nov 2005 Location: San Antonio TX	Measure the resistance between each wire, and each wire and the frame and report the results. __________________ It is error only, and not truth, that shrinks from enquiry. - Thomas Paine

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10th May 2011, 09:01 PM	#3
BZed diyAudio Member Join Date: Jun 2009	What you have is a tapped primary. The black wire is the common connection. The black/red and black/yellow are the hot taps. Generally what these are used for is to give the transformer 115v and 125v taps. Measure the resistance from the black wire to the other 2. The one with the highest resistance will be the higher voltage tap. I would expect the resistance to be nearly the same for both taps, just a small difference. Its possible that it could be a 120v / 240 volt setup. If the black wire to black/yellow reads 30 ohms for example and the black to black/red measures 60 ohms then the black/yellow is the 120v tap and the black/red is 240v. BZ

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