Up until this point, both generations of K5BCQ's printed circuit boards are treated the same. The third generation kit boards had positions that allowed C116 and C122 to be mounted on the new printed circuit board instead of "tombstoning" them (standing them on end and wiring to the projecting end) on the main board. Second generation did not have that feature so we need to tombstone those two capacitors.
With all ten parts mounted on the board it is time to prepare the BITX board for the kit.
Now to re-arrange the preamp power:
Referring to the sketches, locate the TX trace. Use a sharp knife to cut across the trace where shown near resistor R127. Make a small gap, just enough to ensure that it is open. Locate the via on the TX trace near your cut, use a sharp knife to gently remove the coating at the via to prepare it for soldering a jumper wire.
Remove diode D18 (near the "SPK1 jack and C111), thus opening the RX power feed to the audio.
Solder one end of a short jumper wire (something like 24 gauge insulated) to the +12 volt end of R101 as shown and solder the other end to R113 where it connects of R111. This taps the full-time 12 volt supply to U1 and the receive preamp, keeping it active.
Solder one end of another short jumper wire from the R113 end of R111 and solder the other end to the end of R127 next to where you cut the TX trace. This will keep the microphone pre-amplifier constantly powered.
Locate capacitor C116 shown in sketch. Desolder it and gently remove it. Stand it on end on the pad leading to transistor Q16 and solder it in place. The exposed end of this capacitor will be where the receive pre-amplifier will be connected from the "C50" pad (speaker pre-amp) on the new kit board.
Locate capacitor C122, remove it, and solder it on end to the pad leading to Q12. The exposed end will be where the microphone pre-amplifier will feed the new kit board at the "C63" point.
I will leave the option of using plugs and jacks to the individual. I prefer just hard wiring to keep things simple and avoid intermittent connections and to save space. At this point you can install the supplied header pins or just the six jumper wires to the board. Clean off any flux with alcohol or flux remover.
That completes installation. Be sure to check your work before applying power. I have not had any issues with my installations and cannot think of any trouble shooting hints. If you find that something doesn’t work, you might start with voltage checks at the RX, TX, and 12 volt points. An oscilloscope would be the best tool to follow the signal through the gating. Without an oscilloscope I would suggest a signal injector like this example.
I hope that you will enjoy the results of this modification as much as I have. If this is your first venture into the world of surface mount electronics I am sure that you will have picked up some considerable skills, too. Perhaps you will be a bit more comfortable working with these tiny parts and are ready to tackle some more of these projects!
de ND6T