I've recently purchased a Selmer Treble and Bass 50w MkII and it's currently experiencing hissing and spluttering problems when on. I've changed all the valves, but it is still hissing and spluttering.

Does anyone know what the problem could be.

Schematic - http://www.vintagehofner.co.uk/selmer/schematic/tnb7.html
Quote by Kensai
You'll find whisky very different, but try it and you'll grow into it, soon you and whisky are one, but still two, lovers dancing across a frozen lake under moonlight, wrapped in honey and warmth.

Sums up whisky perfectly