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Page 60
Switching On and Testing
If you are feeling confident that you have a good build then
I would suggest inserting a 2A fuse (provided) into the fuse
holder in the IEC socket. Do not install any tubes yet.
I would now try powering on the amp to see if the fuse blows.
If all ok then install the 300B and the 6SH7 tubes into position and power on again – Check to see if the Tubes light up! If
so then that means that a lot of circuitry is working in the amplifier.
Now, the next step is to install the 5Y3 rectifier tube – this will deliver the High voltage to the amp – but read the following
first…
A variac is an ideal device for slowly turning on the AC
voltage – this allows the amplifier to start with 20-30V AC
and you can start checking some DC voltages to see if all is
well.
If you don’t have a variac then we can go ahead with the installation of the 5Y3 tube.
It is important that when you turn the amplifier on with the 5Y3 tube in position that the 300B and the 6SH7 are installed
also – the reason for this is that they load the power supply correctly. Without these tubes installed (300B & 6SH7) the DC
voltages on the power supply will swing up very high and possibly damage the capacitors.
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