Wharfedale evp 15psb speaker

[ChoppedTop]

I have a wharfdale evp 15psb active speaker that has developed a buzz. Its at 50hz (UK). There is a transformer with a centre tap supplying 70v pk to pk.

I have tested the 4 diodes of the bridge rectifier (albeit in circuit), they appear to be ok.

Anyone have any knowledge of these amps?

I'll try and get a pic loaded

[The Dude]

My first thought would be a bad filter cap. Do you see any bulged caps? If you have an ESR meter, do a quick ESR test of filter caps.