I use to repair circuit boards, one thing you need to consider, did something on the circuit board kill the transformer or has the transformer killed other parts on the circuit board. You need to inspect every part on the board then test all the ICs, transistors, diodes, mosfets, and other parts that could be fried inside without showing signs of self destruction on the outside. Check all the capacitors. Inspect resistors for cracks. Sometimes resistors cook on the bottom side where they touches the circuit board. I would never buy a new part for an old board until I know the board is good.