Blackstar 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?

Cheers,

Jeremy

[g1]

That schematic is for the Artisan 10, are you sure the schematic and voltages should be the same as the Studio 10?

[the3secondrule]

That schematic is for the Artisan 10, are you sure the schematic and voltages should be the same as the Studio 10?

Yeah, although the amp is called the Studio 10 - the PCB is labelled Artisan 10, and the Part Designations and test point labels match the schematic.

[the3secondrule]

After some more investigation, the Preamp appears to be working fine and we suspect a fault with the OT

[Mick Bailey]

A shorted turn in the OT won't show up on a resistance check, but If you have a ring tester, that's ideal. If not use the 'neon trick'.

[Helmholtz]

I can't find the output section in the schematics.

If you have a scope I would feed a signal to power amp in and scope the output (with dummy load).