10W HF Linear PA kit assembly
1.00
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3.8 install capacitor C213
Although we intended to install he transformers and inductors first, you can see that C213 is stuck
tightly between T203 and T204, and it will be easier to install it now rather than later. This is a
33pF capacitor with code “330”.
3.9 Wind and install transformer T204
T204 is wound on a BN43-202 binocular core, with a turns ratio of 2:3 using the remaining 0.6mm
(thick) wire. A 2-turn primary and 3-turn secondary. This transformer is relatively easy to wind.
First use a drill bit twisted by hand, to gently remove any rough edges to the holes, that could cut
into the wire.
Hold the binocular core orientated the same as the layout diagram, i.e. with the hole axes
horizontal.
Start the 2-turn winding on the RIGHT-hand side end of the binocular holes. Remember that each
“1 turn” means the wire passes through both holes of the binocular core. So, push the wire through
to the left end, and then back through the other hole to the right; then the same again for the
second turn. The ends of the 2-turn winding therefore both come out on the right-hand side.
Now do the same for the 3-turn winding, this time starting from the left-hand side (with the
binocular core being held in the orientation of the PCB layout diagram). The ends of the 3-turn
winding will come out on the left-hand side of the BN43-202 binocular core.
The only RISK is that you drop the core or somehow mix it up, so that you forget which end of the
binocular core has the 2-turn and which has the 3-turn.
Be very careful to keep a tight grip on this binocular core transformer and remember its
orientation. The amplifier won
’t work well if the 2-turn and 3-turn windings are mixed up.
Insert the two right-hand winding ends (2-turns) in the corresponding two holes in the PCB which
are on either side of capacitor C213.
