problems with transformer or power supply board?

Has anyone encountered problems with the power supply board or the transformer on the t-jet? We haven't been able to get power supply to our T-jet after a slight power surge. The counter light worked, but no power at all. At first, we changed all major components including main board, encoder strip, carriage, print head, ribbon cables, but nothing helped. Finally changed the transformer and it actually powered up. But then we had some issues with the carriage "flying". After a few power ups, it went dead again. No power. We noticed that we had the wires flip-flopped on the transformer and that might have caused damage to the transformer. We're planning to try a new transformer, but before spending more money on that, we wanted to know if anyone else experienced something similar or if anyone have any suggestions.