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P a g e
Always ensure a speaker is connected to the amplifier before powering up or damage to
the output transformer may result. Never unplug a speaker when the amplifier is ON as
this is even more likely to damage the transformer and the output valves.
The output transformer in the V40D has 3 separate secondary windings; a 16 Ohm, an 8
Ohm and a 4 Ohm. This makes it easy to connect many different combinations of
speakers. There are five speaker output jacks: 1 x 16 ohms, 2 x 8 ohms, (wired in parallel),
2 x 4 ohms, (wired in parallel).
So here are all the possible combinations:
1.
For a single 4 Ohm cabinet, use either of the 4 Ohm sockets.
2.
For a single 8 Ohm cabinet, use either of the 8 Ohm sockets.
3.
For a single 16 Ohm cabinet, use the 16 Ohm socket.
4.
For a pair of 8 Ohm cabinets, use both of the 4 Ohm sockets
5.
For a pair of 16 Ohm cabinets, use both of the 8 Ohm sockets.
Always ensure a speaker is connected to the amplifier before powering up or damage to
the output transformer may result. Never unplug a speaker when the amplifier is ON as
this is even more likely to damage the transformer and the output valves.
HT fuse
The HT or ‘High Tension’ fuse protects the high voltage for the valve supply. If this fuse
blows, the first step is to replace it with an identical T500mA 20x5mm fuse. The HT fuse
may sometimes blow due to ‘flash-over’ inside an output valve. This is where during the
manufacturing process, not all of the gas is removed from the glass envelope and the
‘getter’ inside the valve, usually made from barium or magnesium oxide, will burn or
evaporate these remaining gasses resulting in the common silvered internal surface of the
valve. This process, which is more likely to happen with new equipment, draws high
current momentarily and can blow the HT fuse. It will rarely cause any damage so just
replacing the fuse is sufficient to get the amp running normally again.
However, if the HT fuse blows again, it may indicate a serious valve failure where internal
parts of a valve are shorted and in this case the amplifier needs to be checked by a
qualified engineer to assess the problem.
Output power switch
You can run your V40D at either high or low power. This switches between full high
tension voltage and around 60 per cent of the high tension voltage, thus lowering the
output power to around 7 watts and enabling the output stage to be pushed into
overdrive much more easily.
