Marantz 22xx AM section Diagnosis and Repair -- Help Required

I have been refurbished about fifteen 2270's and the section that gives me the most trouble is the AM circuitry.  I have replaced all transistors, diodes (1N60) and capacitors but that does not guarantee a fix.  The AM section usually ends up with a lot of buzzing and may only pull in two or three stations.  I have a scope, signal generator and a VTVM.  I usually have to resort to buying a P150 board on eBay.  I am willing to purchase more diagnoatic gear if it does the trick. Any help woud be appreciated. Thanks. Ray


Any chance you are working around florescent fixtures & lights or light switches with dimmers?  That would be the cause of buzzing.