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When fitting C2 (22uF electrolytic) capacitor, PAY ATTENTION to the polarisation of this capacitor! There
is a white stripe along one side of the capacitor, this is the negative wire. The positive wire is indicated by
a “+” symbol on the PCB silk screen. Don’t get the capacitor the wrong way around!
4)
Install noise filter circuit components
Install components R3, C4, R4, C5, R5, Q1, Q2, Q3 and
R6. These components are in a line along the top of the
board parts layout diagram. For convenience I
recommend working from left to right. These
components are all part of the noise filter circuit. This
circuit takes 5V input and produces about 3.5V output for
the Si5351A chip, resulting in a very highly filtered low-
noise supply.
Pay careful attention to the polarity of C4 and C5 (22uF capacitors). The positive lead is indicated by a “+”
symbol on the PCB silk screen, and the negative lead on the capacitor is indicated by a white stripe.
When installing Q1, Q2 and Q3, be sure to correctly identify which are the 2N3904 (NPN) and 2N3906
(PNP) transistors! They look the same
– so carefully check the writing on the side of the transistor. The
2N3906 PNP transistor is fitted in the Q2 position, the central one of the line of three transistors. All three
of the transistors will need their central wire bending outward to fit the triangular pad pattern on the PCB.
Make sure the transistors body shapes are aligned with the shapes printed on the PCB silk screen. Note
that Q2 (the 2N3906) is “backwards” compared to Q1 and Q3.
5)
Fit switches, button, LED and resistors
Fit the switches S1 (4-way red-coloured DIP switch), the
push-button S2, 3mm red LED, and remaining resistors
R7 and R8 (both 560-ohm).
Make sure the “ON” printed on the 4-way DIP switch is
aligned as shown in the photograph (right). Do not worry
about the fact that the PCB silk-screen printing identifies
the switches as “8 4 2 1” whereas they are labelled “1 2
3 4” on the switch body itself; and “ON” is in a different
place on the silkscreen compared to the actual switch!
6)
Fit two 10-way header sockets
Here the two 10-way header sockets should be fitted
and soldered. They are a little loose in the holes so it is
important to align them well so that the Si5351A Synth
module kit will plug in cleanly without stress. I find that
the best way to do this, since you have already
assembled the Si5351A Synth module, is to plug the
Synth module into the sockets, then fit the sockets into
