Yvette:
I'm not clear on your question, but will take a stab at offering at least something useful.
Do you have an Owner's Manual for your camper? I find one for a 1977 Hi-Lo on this forum. If you haven't found the Library here, go to the home page, scroll down to almost the bottom of the page and you'll see a section entitled "Library". Look beneath there and you'll find a button by something about "Owner's Manuals". Here's a quick link to the '77 manual. Don't worry, a '77 is probably very close to your '75:
http://www.hilotrailerforum.com/f49/...7-2577-a-1117/
In the '77 Owner's Manual, turn to page 8 and there are a series of troubleshooting steps to take for "IF UPPER SECTION WILL NOT LOWER" and it walks you through some possible problems. Number 2 under that section looks like what you might be trying to describe. That #2 states "If the safety catch does not release and lift motor runs and does not make a loud squeal, the lowering valve is blocked in open position." It then goes on to give you three remedies to that problem.
I'm just guessing that when you say, "reset brake", you're referring to the safety release cable, but that's just a guess. I don't know of anything on a Hi-Lo called a "reset brake".
Good luck!