The short answer is DO NOT attempt to repair ANY medical device unless you are qualified, as in Biomedical Engineer!
Medical devices must pass rigorous testing, and standards. Doubly so when it comes to electrical/electronic devices due to the danger of electrocution. ALL transformers used within medical devices are ISOLATION TRANSFORMERS to isolate the patient side of the device from the AC power supply side of the device. You cannot just buy, and use any old Chinese made, off-the-shelf parts in medical devices. You're just asking for fire, injury, or death! DON'T BE CHEAP! Either have this repair done by the manufacturer, a qualified Biomedical Engineer, or bin it and buy another one. I know about which I speak. I'm a now retired OR RN of 30 years that is highly trained, and qualified. I am trained, and qualified to do adjustments and calibrations on certain devices, and equipment. I worked closely with Biomedical Engineers, and other qualified individuals. Please do not risk your life or that of others to save a little money.