Nice, good sluething so far.? I agree with your assessment.? Hopefully the fault is easy to find now.
For 20m, the band select should be set for filter "3", which is B4 or pin 1 on IC408.? So that means the signal is going out on pin 1, through L403, and back to pin 2, so you see it on both of those pins.? That also means those two connections to L403 are likely good (or shorted).? The signal at the input of IC402 (pin 11) verifies that something happened in that coil which shouldn't have happened.? Maybe shorted or open windings, or its output not soldered well..
?
The signal doesn't split into I/Q until after the T401 trifilar transformer, from its outputs into IC403.? The frequency of the signal will change to about 12kHz out of IC403 and into the reset of the path to the PCM1804, since IC403 is the mixer.
?
Stan.
