take an alligator clipped jumper wire and bypass the LPF section - get as close to the receive mixer as possible - and see if you have signals.?
idea number 2 is that the LO is not getting from the PLL to the mixer - check to see how the connectors are seated.
okay I should have listed this first - your BFO calibration may be way off - as mine was.? search the list for v5 bfo calibration - this could be the issue.? if so, when you tune the upper portion of 40m in the evening you might get something when you tune across big AM broadcast stations.?
73 curt
