I had a 7700 (now have an 8900) and thought mine was broken because it wouldn't stay up. It was the dreaded "operator error" although I have to say the manual wasn't exactly clear on this. When you put it up, there is one position where you can also pull it forward a tiny bit. When you do that, that will lock it in place and it will be out of the way. As I recall, I was also trying to push it up higher than it needed to be, so try pushing it up about 2/3s of the way and then pushing it forward. You shouldn't have to force it once you find the right spot.
I'm posting this on your other thread too.