I fix these machines for a living as a indenpendent roll laminator repair station around pittsburgh pa...
as you have mentioned the top clear plastic shield MUST BE DOWN, the pin on the feed tray MUST be tripping the interlock switch! The fuse holder near the reverse switch MUST have a good fuse and the fuse holder itself often go bad and cause no power problem.
theres a thermal fuse and temp sensor under the center of the bottom red roller. what can happen is the tiny temperature sensor board fails and the machine overheats, taking out the thermal fuse. feel free to call me if you have questions.
theres also a 1 amp or so fuse under the main board, if it blows it can cause no power
bob haller service and sales pittsburgh pa 412 366 4906, September 2012