Footswitch socket
Channel F/S. Connect the supplied single way latching footswitch here to select Channel 1 or 2.
Single Ended Mode switch.
This switch, located through a hole in the rear grill, is used to switch off either of the 2 output valves.
This results in the amplifier running ‘single-ended’ which is a very pure Class A mode. If the front panel
power switch is on LOW, in single-ended mode the V30 produces around 1.4Watts rms. This should
allow playing at home without getting lynched by the neighbours. The switch throws both ways to
alternate between each output valve for even wear if this mode is used extensively.
Biasing:
Whenever any output valves are changed, the amplifier will need to be re-biased. This must be done by
a qualified or competent person as there are lethal voltages inside the V30 and getting killed by a guitar
amplifier is a rubbish way to die. Also take care as valves may still be very hot from use.
Please always try to buy matched pairs of output valves as they will be easier to Bias and give longer
service. Ensure the toggle switch on the top of the chassis is in the correct position for the selected
output valves, (either 6L6s or EL34s).
Unplug the V30 from the mains and remove the bottom chassis plate using a No.1 Posidrive screwdriver.
Unscrew the 4 x M4 screws from the side of the top grill using a No. 2 Posidrive and remove it. Carefully
place the V30 on a clear and secure surface upside down so all its soft bits are exposed.
The BIAS pre-set is found on the power supply PCB, (yellow circle on photo). The Bias voltage
measurement is performed between the chassis and the test point TP10 & TP11, (yellow triangles on
photo). Using a multimeter set on the 200mV range, measure these test points and adjust the BIAS
preset so the meter reads approx. 34mV. This translates into 34mA of current per output valve. Check
both Test Points a few times and try to balance the Bias voltage so it is as close as possible between the
2 valves. We don’t recommend a difference of greater than 6mV between the 2 valves.
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