I just installed a Sears Craftsman 1/2 HP Garage Door opener - it was working fine through adjustments until it closed too tight as I was doing the adjustments to keep the door closed. I disengaged, reset the door arm and tried to re-engage by running the opener but it just hums - the Cable side is dangerously tight and the motor unit won't release the tension, and the chain is sagging on the other side of the chain spreader / motor unit. Is there anyway to release the tension on the Motor unit manually? Or is there maybe another solution to my problem?

I did that, as I mentioned by 'disengaged' in my original post - and yes, it was hard to pull - it was really tightly closed! Ultimately, the problem was it just wouldn't go 'UP' - I ended up taking the back casing off the unit off and found that in doing my adjustments I had dis-lodged the 'up' adjustment plastic screw so popped it back into place & it worked again! Thanks anyway. I did that, as I mentioned by 'disengaged' in my original post - and yes, it was hard to pull - it was really tightly closed! Ultimately, the problem was it just wouldn't go 'UP' - I ended up taking the back casing off the unit off and found that in doing my adjustments I had dis-lodged the 'up' adjustment plastic screw so popped it back into place & it worked again! Thanks anyway.