Before finishing your kit you must decide what 35 to 40 khz span of frequencies you want to work. Or, you might have completed the kit and can't find the span of frequencies you desire.
It is best to leave C7 off until you have the transceiver fully functioning on transmit and receive. Studying the right column on Page 13 you will see that you should have a good carrier on transmit somewhere around 7.230 with the tuning pot at the highest frequency, T2 and T3 peaked, and the R24 power adjust pot at just below the highest output power setting, around 1.90 watts. DO NOT proceed until you fix the carrier problem and the frequency problem. It could be the wrong number of turns on toroid L1 (you may need to remove a turn on L1 if the L.O. is too low), or improper capacitor in the C3, 4, 5, 6, 8, 9 position. Before proceeding the transceiver must be transmitting on around 7.230.
In the scan above, a 100 pf capacitor was installed in C7 and tuning knob was set in the middle. As you can see from the spectrum analyzer above, the VCO is sitting right on 3.065 which is exactly 4.000 mhz below desired frequency 7.065. Without C7 installed and tuning knob at highest setting there should be a carrier at around 3.230 khz (4 mHz below the desired frequency).
From the above, you can troubleshoot the VCO without transmitting by tuning your "big rig" to just below the 80 meter band to find your VCO frequency. A small wire for an antenna from your "big rig" antenna input loosely placed near the VCO which is around L1 toroid will help you hear the signal. This way you won't have to be transmitting all the time when troubleshooting or selecting the C7 capacitor. With an antenna connected to your kit you should tweak T1 for maximum noise or a maximum carrier from a received signal.
When selecting the C7 capacitor DO NOT solder it in place yet. Form the leads on each C7 capacitor in a bowleg as shown below. This will make for a good temporary contact and keeps the capacitor from falling through board and possibly touching metal.
Place capacitor in C7 holes in circuitboard. It will make sufficient connections to tune the local oscillator so you can select the correct value before soldering.
Once you're satisfied you have the correct span of frequencies you can solder C7 in place WITH POWER OFF. Peak T2 and T3 into a dummy load and adjust R24 for output power just around 1.95 watts or so. Try not to exceed 2.1 watts or you'll hear some RF getting into other parts of the transceiver and you'll hear a raspy sidetone. Do not transmit without a load connected. You will possibly damage the output transistor.
Make sure your power supply is at least 12.6 volts.
Some of you might want to put a switch in to change C7 to select different areas of the 40 meter band to operate. This can be easily done since one end of C7 is ground. You may have to play with the C7 values since you are adding stray capacitance to the VCO tank circuit and the published frequencies on Page 13 will be slightly off. You can fine tune your desired span using junk box capacitors as long as they are temperature stable NPO or C0G types. Otherwise slight temperature changes will cause your desired frequency to drift.
If you want to replace the tuning pot with a 10 turn pot, you may want to also replace C8 with a higher value to span about 100khz. But do not expand any further due to instability. The C7 values will need to be juggled around to set your desired range too.