KiT 6550 Hum

[TimN]

I thought I would test the valve amplifier waters with a second-hand purchase from ebay with a KiT 6550. Having assembled it by pushing the valves into the holes and switching it on for the first time there is a definite hum/buzz emanating from it. At first switch on it sounds a bit like an electric loco powering up. If I put my hand on the surface in front of the transformer there is also a vibration that can be felt.

As I said, I have never owned a valve amp before but I do not think this is as it should be. I can hear the hum/buzz from across the room.

I have played some music through it and it sounds pretty good from both channels. If I turn it up loud enough I can't hear the hum/buzz either! It hummed/buzzed without a source plugged into it also.

Can anybody suggest me a course of action to track down the source of the hum/buzz and eliminate it? I am quite a novice at tinkering with hi fi, but can probably work my way through it with some help. Reading through other posts, I believe that it may not necessarily be the transformer at fault.

Can anybody please give me some help and guidance?