Studio 10 EL34 - low output

[the3secondrule]

Hi All,

I have a Blackstar Studio 10 EL34 on my bench here with very low output volume.

Voltages in the Preamp all seem out of whack - measured voltages as follow (expected values per test point in brackets)
Power amp voltages seem OK.

TP2 +15v
TP3 -15v
TP4 +428v (435v) - HT Ref
TP5 +398v (390v) - HT2
TP6 +347v (290v) - HT3
TP7 +336v (275v) - HT4
TP8 +42v
TP9 +12.8v (+12.6)
TP10 +250v (200v)
TP11 +300v (300v)

Any suggestions on where i should start looking?