AMP MAKER N5X - Page 37

Testing without valves
We now move on to check the same voltages we checked after building the power supply. Write your
gures down in the rst column of the above chart.
• First, use your DMM to measure the AC voltage at the IEC socket.
• Then do the same between points A and B in the diagram below. You should get approximately
430V.
• Now check the AC voltage between points C and D. You should get a reading of about 6.5-7V.
• Select the high DC voltage range on your DMM and check the voltage between points E and F. The
expected reading is 290V.
• Turn the Power level control all the way up. Check the DC voltage between E and G for a reading of
about 285V.
• Dial the Power control to minimum and the E-G reading should fall to around 25V
If the readings are all correct, switch o the amplier and unplug the mains cable before moving on to
the next step. Contact Amp Maker if you get any odd readings.
Testing with valves
Insert the valves: an ECC83 into V1 and either an EL84 into V2 or a 6V6/ 6L6/EL34 into V3. Set all of the
amplier’s pots to minimum, except the Power level control - set that to maximum. Put the Boost switch
in the centre and the Bypass switch up. Make sure there’s no guitar plugged into the Input, but do plug a
suitable speaker into into one of the outputs. Plug the IEC cable into the mains socket and switch on.
Start by repeating the measurements you did with no valves installed, and record the numbers in
the correct column of the chart (depends on the valves you are using):
• Mains AC voltage at the IEC mains socket (may have changed a little since the rst test, depending
of time of day, etc)
• AC voltage between test points A to B may read slightly lower now that the transformer has a load.
• The heater supply at C-D may also be a fraction lower – typically 6-6.5V
• The DC voltage between test points E-F will also be lower, around 250-260V
• Measure the E-G voltage, typically around 250V.
• Turn the Power level to minimum and remeasure E-G, typically 25V.
Final measurements
That last set of measurements lets us know that the power supply board works properly under the load
of the circuit. The remaining measurements let us check the DC state of the rest of the N5X amplier
circuit at idle. From this we do a few simple calculations to check everything's within spec and then
we're ready to play.
So use the
annotations on this
diagram and measure
and record the rest of
the voltages in the
same column of your
chart.
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