# Output Tranny secondary values...

Discussion in 'Amp Tech Center' started by schmee, Jan 8, 2020.

1. ### schmeeDoctor of Teleocity

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If I have an unknown Output Transformer which has multi tap outputs, can I easily determine which is which? One is 2 ohm, one is 4 ohm and one is 8 ohm.
However, I have noticed that there is no industry standard for wire colors.
In fact even within one maker, the color codes may be different on different size multi tap output transformers...

Would an 8 ohm tap have more winding and thus be easy to measure and compare with another winding that is lower resistance?

I know measuring OT's can get complicated, but I just need to compare outputs. I know they are 2, 4 and 8. Just don't know which one is which for sure.

2. ### FacemanTele-Meister

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Try this video...

King Fan and Junior Little like this.
3. ### petebFriend of Leo's

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They are going to measure very close to each other. Not 2 ohm, 4 ohm, or 8 ohm. They will all measure less than one ohm. You could try measuring to see which is highest, lowest and middle.

The right way would be to put some AC into the primary and measure the AC on the secondary, determine the voltage ratio, find the winds ratio and then the impedance ratio and impedance.

4. ### zookFriend of Leo's

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You determine the turns ratio by using the outside windings of a push-pull transformer, ignoring the center tap. You can determine the turns ratio by using 9VAC (think wall-wart) on the primary. Example: 9 VAC on the primary = .270 VAC on secondary. Turns ratio = 9/.270 = 33:1. Impedance ratio = (33 x 33) = 1089:1 which would equal an impedance of 8712 ohms working into an 8 ohm load (1089 x 8). 4356 (1089 x 4) into 4 ohms. and 17424 (1089 x 16) into 16 ohms

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