Tighten Garage Door Chain - No Trolly Adjustment
First time on here. I recently bought a house and it came with an older 1/3 hp Beaver garage door opener. The chain has become loose to the point it wont open. It is a tube track unit, with no chain adjustment on the trolly. Through some research it looks like the tension adjustment is on top of the drive. I found the screw adjustment, but it does do anything. I do not have a manual for this unit (nor can I find one) and I am stumped. I also have limited space between the drive and the ceiling of the garage to work.
Does anyone have any idea how to tighten this chain (short of getting a new one)?