Long time ago, was riding one of our 76-3er from Europa to Vancouver. After the beautiful sights of "Green"land and a little chat with Thule we started to get light fumes in the cockpit, visible and smelled it. Wasn't too bad but almost 2 hours from our alternate Yellowknife it required some attention
After some troubleshooting including killing the power to the galleys, our Purser had been informed and the 1st class gal came back with the info that there was a rattling noise under the galley floor at door 1R. In concert with ops we decided to switch the avionics cooling into override I believe. FA came back and reported the noise to be gone. We checked the galley and the floor, no smoke no heat and the fumes in the cockpit disappeared. We decided to continue to YYC but ready to divert to Yellowknife(they have a McDonalds there that provided dinner for another 76 of ours that diverted there because of an engine fire), or Edmonton further down the line if needed. We choose YYC not just because it was our destination but also the weather being VMC all the way down, unlike Yellowknife and Edmonton. We were aware that the avionics were cooled by diff pressure now and that at lower altitude it wouldn't work as well, resulting in possible loss of all our glass instruments etc. Briefed the arrival into YYC extensively and were prepared to fly the bird on the stby instr. After an uneventful descent/approach and enjoying the beautiful scenery the glass panels were starting to fade out and completely fail in the flare. They found the avionics fan bearing completely torn up, next day new fan and back home.(We bought the FA who brought our attention to the noise under the galley floor a nice little gift