MC275 Hum Conundrum
 

I replaced most of the caps in my MC275. Power up test revealed a loud hum. Making sure of my wiring I chanced to approach capacitors C1 and C12 with a pair of needle nose pliers - the hum got substantially louder perhaps 6 - 9 db or so. An aluminum framed magnifying glass also increased the hum. A plastic pen did not.

What do you think?

Thanks in advance and Happy Fourth.