QRP Labs QCX-mini CW, Assembly Instructions Manual, Page: 110 / 121

If you do NOT see any power output on key-down, then you probably have a fault in the
Power Amplifier. A common mistake, as I mentioned previously during the assembly steps,
is failure to remove or burn off the enamel insulation on the enameled copper wire wound
onto the toroids.
Check the RF power wire touched to the BS170
drains first (see diagram). You can still touch the
wire to these BS170 drains from the top side of
the board. Key-down and check the wattage
reading. At this point the indicated power will be
even less reliable than across the dummy load.
But at least see if it reads some watts.
If you see power output at the BS170 drains, but
not at the overall transceiver RF output, then this
means that the fault lies in the Low Pass Filter.
Check the soldering and the enamel situation, on
those toroids.
If you do not even see power output at the BS170 drains, then perhaps the L4 drain
inductor in the PA has incorrectly soldered wires, that have not made an electrical
connection – so check the L4 wires first and make sure the enamel is properly scraped or
burnt off, to make a proper connection.
QCX-mini assembly Rev 1.05
110