10W HF Linear PA kit assembly 1.00 14
To test the “C” single-wire winding, connect the DVM probes to the top pad of R210 and the
bottom pad of R209. If you do not see DC continuity, go back and check the C winding soldering
joints.
To test the “B” bifilar winding, connect the DVM probes to the left side pad of C204 and the
indicated pad of the Q203 transistor. If you do not see DC continuity, go back and check the B
winding soldering joints.
To test the “A” bifilar winding, connect the DVM probes to the left side pad of C204 and the
indicated pad of the Q204 transistor. If you do not see DC continuity, go back and check the A
winding soldering joints.
Again, it is wise to check for any shorts between the C winding and the A/B windings. You should
not see a DC zero resistance (continuity) between any A/B to C test points. On the other hand, A
and B test points will show DC continuity between each other since the windings are connected in
the circuit.
3.7 Wind and install transformer
T203
T203 is wound on a FT50-43 toroidal core. It consists
of 10 turns of bifilar twisted 0.6mm wire.
10 turns of wire on a 0.5-inch size toroid will require
22cm of bifilar-wound wire. You should therefore start
by cutting say, 50cm of the 0.6mm wire. Prepare it by
twisting it tightly together the same as previous bifilar
wires. Wind 10 turns (10 times through the hole in the
toroid).
Untwist the ends, and tin the wire ends. This thicker
wire does not so easily burn off the enamel by the solder blob method. So, I find it helpful to
scrape the wire ends a little using a wire-cutter, THEN tin them with solder for 10 seconds.
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General