Fairlight-CMI

I wasn't expecting to launch a new call for help so soon on the forum. But unfortunately here goes...

I use my IIx a lot for sampling and have always used the line input to do so.

Now, the line input as well as the mic input don't work anymore. Page 8 shows no incoming signal.

The ADC direct input still does work and I can sample using that input in combination with a DI-box. 
So the problem doesn't appear to be with the CMI02 card.

I've checked the XLR connectors and the cables that go to the CMI-04 board. These connections are still OK. I've also checked the 10-way ribbon cable that goes to the CMI02 card and it's also OK.

I'm having the exact same problem with a second IIx (the one that I was able to bring back to life a few days ago).

My first guess is a problem on the CMI-04 board. But before I start debugging that board I'd like to hear if anyone else has ever encountered this problem and knows what the origin of it might be.

Best,
David