The difference (main) between Rev C and Rev D is the addition of a speaker mike capability. Thus, an additional pin is added to the printed circuit board. The speaker/mike will work with either Rev C or Rev D boards, but you would have to run a wire to the microphone connector (Pin 8) from the speaker connection.
A couple of issues that I have found with power output are as follows. Make sure that you have wound the toroids properly (easy to miss-count). See: http://www.larvell.net/Side_Left_B/files/KN-Q7A_App_WindingTheToroid.pdf
for additional help. Make sure that the wire leads have been properly stripped. With an ohmmeter, you can check the points on the printed circuit boards for the coils making contact.
The next issue is to check the Transmit Band Pass filter for proper tuning. If you have a signal generator and an oscilloscope, you can adjust the filter without power to your radio. I inject the signal at pin 4 on the NE602 and check the signal with the oscilloscope on the 680 ohm resistor. Adjust the coils for maximum amplitude.
If all that fails, Short Pin 2 and 3 on the NE602 nearest the IF crystal. This will take the radio out of SSB and you should transmit only the carrier wave.
Check to see where you are loosing the signal. With an oscilloscope check the amplitude on Pin 4 of the NE602. Press and release the push-to-talk button on each test. Next look at the amplitude on the SMD part C3357 on the tab. The amplitude should have increased. Next check the amplitude on the Collector of the D882 transistor. Again, the amplitude should have increased. Finally, check the amplitude on the 104 cap that leads into the final High Pass Filter section. You should get a very large voltage swing.
One other thing that I will do just to check the transmit section would be to inject a small signal at the carrier frequency at the 680 ohm resistor. Try about 50 mV to 100 mV if possible. Then check each step of the transmitter with an oscilloscope.