Manufacturers consider cost savings, but also in order to reduce the size of the medium-frequency voltage transformer are now generally used ferrite core.
The damage to the IF transformer is generally limited to the internal turn-to-turn short-circuit, that is, a turn (circle) and the neighboring turn (circle) between the insulation damage caused by a short circuit. As a result of a short circuit at a certain point, it is difficult to detect a good or bad with the general electrical instrumentation.