% error for primary resistance

[tenderland]

Hello I just recieved my output xformers and checked out the dc resistance . the secoundary are identical . The primary , one is 39 ohms
the other is 47. The spec sheet indicates 40. This is a 17% error , is this acceptable ?

thanks
J

[Brian Donaldson]

I think not I would expect 5% tollerance, but 10% would be acceptable

[SY]

That's not terribly unusual. For less exotic winding geometries, the outer windings will have the same number of turns as the inner windings, but because they're farther from the center, the length of each turn is longer so the resistance is higher. You'll also see a bit higher leakage inductance from the outer layer, which is why you'll sometimes see compensation caps that are not symmetric side-to-side.

[tenderland]

These are Plitron pat -3025 very expensive torodial output xformers , I would think they would be closer

so more exotic windings like toroidal should have less of an error?

[tenderland]

Good thing im anal and measured the resistence , it seems they shipped one correct xformer 3025 and one incorrect 3035, the box was correct though.