How to Set Limits on Older Chamberlain/LiftMaster/Craftsman DC Belt and Screw Drives 

This video shows how to set the limits and force on older Chamberlain made DC motor openers. This video applies to the following models:
LiftMaster:
2500B, 2500D, 3500, 3840, 3850
Chamberlain
HD800D, HD900D, 248754
Craftsman
139.53919, 139.53919D, 139.53918D
Raynor
3850RGD
This also works on some of the jackshaft openers but there's a couple extra things to pay attention to when programming a jackshaft which is why I don't mention them.