Transformers rarely fail. If the transformer buzzes very loudly,
gets very hot very quickly, and its output voltages are wrong, then
the transformer is probably going bad and should be replaced.
Most problems attributed to the transformer are really a failure
elsewhere. Cold solder joints, broken wires, bad fuse holders, bad wall
plug, broken switches, and bad connectors symptoms are often mistakenly
blamed on the transformer. Be absolutely certain that the transformer has
failed before going to the bother of replacing it.