I am feeling with you. You should really check clock 0 and clock 1 with a scope. If you have a two channel scope, you should even observe the 90° phase difference between the two clock outputs of the DDS chip which is required for the Tayloe detector. It is strange that clock 2 (for transmitting) seems to be working still, but otherwise .....? I'd be interested how to remove such SMD devices from such a densely populated PCB without frying other componentes thermically and how to get replacement devices back in without thermal problems and without creatings shorts between the narrow speced legs.
Frying semiconductors can be interesting, As I have found out (not really deliberately) BS170s generate a lot of smell and astonishingly much smoke for such a small transistor, howeever MPS751s (Q6) only crack up noiselessly, not much dramatic effect there. But both devices have only three leges and are much easier to remove ;-) than a SI5351A or FST3253.
73, Klaus DL2QB (WN2Z)
P.S.: Reading your vita and that you were working for a major aerospace company: You weren't involved in the Apollo 13 mission (the one where a oxygen tank blew up midway between Earth and Moon), were you?
This is the fried Q6
Klaus Beckers