Hand wiring back end Blackstar HT60 Soloist

[Steve Blackdog]

Hi there

This is my first post, so thanks for letting me join your forum.

I have a main PCB for the Blackstar HT60 soloist and want to do something useful with it. Has anyone any views on whether this is even achievable? Not sure if it will possible, or simply too much grief.

Any thoughts?

Cheers

Steve

[Steve Blackdog]

I have just re-read my post and perhaps should clarify...

My choices are:

Pull it apart and use the part; or
Try to find original blackstar rear pcb, power transformer plus an appropriate OT and rebuild as far as possible from OEM parts; or
Make my own rear end for the main HT-60 pcb, but not using OEM parts.

Of course, I could put it in a drawer and forget about it. I paid £30 for it, so I have a little headroom.

Finally, there are many threads on here about the challenges getting hold of Blackstar schematics. I have emailed Blackstar, but not heard back.

All the best

Steve

[Jazz P Bass]

Try this for a schematic: https://music-electronics-forum.com/...8&d=1519629152

[Mick Bailey]

If it is a used PCB be aware that many of the earlier amps suffer from a breakdown in the PCB substrate around the phase inverter MOSFETS (usually these are IRF830) At the same time this overheats the nearby PI coupling caps (1uf/450V). There's also often DC leakage across the board between the L.H coupling cap (as viewed from the component side) and the power resistor leg that's located above and slightly to the left.

The fix is tricky and sometimes there's leakage around the preamp tube pins. The official line is to replace the PCB with a later revision. You could got to a lot of trouble building up an amp only to be disappointed. Why was the board removed in the first place - do you know the history?

Symptoms of board failure are:

Extremely low output
'Voice' selector switches kill sound when in (clean) channel, or out (drive) channel.
Excessive voltage drop across drain resistors at idle
Excessive voltages on gate and source pins of PI MOSFETS.

[Steve Blackdog]

Thanks, chaps.

I bought the pcb as new, but with the volume pot snapped off. The price reflects the risk I am taking as list the main pcb is ridiculously expensive (£300ish). I agree that it would be very frustrating to find the pcb has an inherent fault.

Any thoughts on whether wiring a diy back section might be feasible?

Cheers

Steve

[Mick Bailey]

You could simplify it by not having an emulated line out or selectable loop level. The speaker sockets tie into the amp standby circuit, but if you wanted you could wire it to operate like any other tube amp speaker arrangement.

[Steve Blackdog]

You could simplify it by not having an emulated line out or selectable loop level. The speaker sockets tie into the amp standby circuit, but if you wanted you could wire it to operate like any other tube amp speaker arrangement.

That’s a very good idea. I doubt I will ever need an emulated line - not missed never having had one on any amps in the past.