Hi,
i accidently fed 15 watt RF into port 1 of my V2 Plus4. The first MXD8641 near the port then had a hole and released all of its magic smoke.
I replaced it (and later all other MXD8641, too) but the problem remains:
All traces show only noise, like nothing is connected. And nothing changes when you connect a short or load the the port.
S21 measurement also shows no difference wheather you connect a loop cable or not.
When i connect a spectrum analyzer to port 1, i see the sweeping frequency of the chosen span range, but only at about -80 dBm.

Is there a debug-function or special firmware to check the parts on the board separately? It is kind of difficult to measure around, because there is so much switching going on, and you have multiple signal sources, etc.

In the schematic i see the transformer of the directional coupler - I can't find it on my board. Is it on the backside beneath one of the black epoxy drops?
Maybe that transformer got damaged?

Thanks for any help!

Sounds like mine.  I blew it with switching transients introduced on the feed line by bias-Ts. It looked fine under the microscope and I replaced the MXD8641, but that didn't fix it.