I have noticed that they are sometimes a bit asymetrical when measured from the center tap and have heard that with some, since the first set of windings are closer to the core, they use less turns than the outer winding, which is further from the coil and having more windings. The resistance should be close, but it might not be exactly the same for both sides. I have seen power transgormers that still worked sort of , but ran hot and that was because a portion of the windings do work but they were shorted part way through the windings. If it runs excessively hot or if you see the tar stuff dripping out that might be a bad sign. You should replace the filter caps first, as it is common for the power supplies’ electrolytic filter caps to short and then burn out the power transfomer because of that.
