Hi ya mate, I had mine serviced last year, as it was coughing and splutering. It sounds like you may have a few little problems, or such like.
Mine had one bad valve, resistor damage, numerous dry joints and it had to have the transformer reterminated, basically, it had over heated in the past, all taking 3 1/2 hours to do. (Just looking at the receipt now).
I took it to Dave Lunt in Stockport, it cost me £100.
Anyway, it has worked beautifully since and is completely silent.
Get in touch if you need 'out else.
Steve.