I have a pair of 3115 crossovers that use a tapped inductor. The schematic shows the inductor to be 3.85 mH across the blue and black, with three taps, red, white and green, along the way.
I opened the crossover and cut the blue and black leads away from the circuit so I could measure the inductances. The R/W/G go directly to the HF +, so nowhere with no speaker and are disconnected.
With one probe on the blue wire, I read 0.90mH to the red, 1.29 mH to the white, 1.78 mH to the green and 3.63 mH to the black. The black should be the 3.85 mH and 6% is within tolerances. No problem.
OK, now the fun starts!
I would think that if I put a probe on black and a probe on green the value should be 1.85 mH (i.e., 3.63 - 1.78), but is 0.35 mH
Black to white should be 2.34 (i.e., 3.63 - 1.29), but is 0.63 mH.
Black to red should be 2.73 mH (i.e., 3.63 - 0.90), but is 0.98 mH.
And...,
Red to white should be 0.39 mH (i.e., 1.29 - 0.90), but is 0.06 mH
Red to green should be 0.88 mH (i.e., 1.78 - 0.90), but is 0.17 mH
White to green should be 0.49 mH (i.e., 1.78 - 1.29), but is 0.03 mH
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