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The "Heat" connection should be connected to +5V also, if you are using the OCXO version of the
Si5351A module. It provides +5V to the oven heater, using a thick track on the PCB. This avoids
voltage drop on narrow traces. If you are using the non-OCXO version of the Si5351A synthesiser
module, then you do not need to connect the "Heat" connection.
Also pay attention to the jumpers at R3 and R4 on the right-hand side of the diagram. R3 is an
optional resistor, to be fitted to enable in-circuit-programming for those wishing to update their own
firmware and having the necessary equipment.
If you do not fit a 100K resistor for R3, then you must fit a wire jumper here as shown.
Resistor R4 is an optional resistor, which is in series with the top of the contrast adjustment
potentiometer R1 and +5V. Typically the contrast voltage required is less than 1V and the
adjustment is rather sensitive. If you wish, you can fit a 220K resistor in this position, which will
make the contrast potentiometer less sensitive to adjust.
If you do not fit a 200K resistor for R4, then you must fit a wire jumper here as shown.
9) Solder in transistor Q1.
If you have purchased additional transistors
for Q2 and Q3 to increase the power output, I
still recommend starting with just the basic,
single transistor, 5V PA supply setup. Get
things working basically first, then later install
the additional transistors. Walk before you try
to run!
The transistors are located at the edge of the PCB with their flat side outwards. This is to allow easy
attachment of a heatsink if desired (for higher voltage and hence higher power operation).
10)Install two 16-way connectors on the main PCB and LCD.
Install two 16-way connectors on the main PCB and LCD. Either way is fine, but my
recommendation for installing the LCD connectors, is to use the female (socket) connector on the
LCD side and the male (plug) on the PCB side.
7
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