Only one(1) tv is not working out of four(4).
Everything working for years.
Running setup test shows SWM not detected error code 51-750.
Went to main tv with SWM unplugged from wall.
All other two(2) TV's went to 771.
unplugged those 771 from wall outlet.
Went back to main, plugged in SWM to wall outlet, unit restarted with green light.
Went back to one(1) tv plugged back into wall, turned on, and it started - OK
Second tv(the problem one) plugged back into wall outlet, turned on - AGAIN 771
DirectTV came, said need to rewire home......