Ive fixed quite a few buzzing transformers over the years ,
I use a small paint brush to place drops of varnish between the core and bobbin ,9/10 times thats enough , once or twice I dipped the entire transformer in varnish but thats bigger job .
I use a small paint brush to place drops of varnish between the core and bobbin ,9/10 times thats enough , once or twice I dipped the entire transformer in varnish but thats bigger job .