Garage door opener - no juice to sensors

Hello- I've had a problem come up with my garage door opener. Its a Craftsman (41A5021-2C) 1/2 hp model - about 8 yrs old. The LEDs on the safety sensors are out (and don't work), and using my trusty multimeter I'm able to determine that there is no juice getting to the sensors. I've been able to determine that the wiring is ok (disconnected and used ohm-meter) - no shorts there, all connectors ok, etc. I'm left with the assumption that there is a problem with the power going from the main unit to the sensors. There are three terminal screws: #1 (red) goes with #2(white) for the door controls. #2 goes with #3(red) for the sensor connections. There is juice between 1 & 2, but not between 2 & 3 (assume there should be) which makes me think there is a problem with power coming from the red #3 connector (which goes to the sensors). I took the circuit board out and visually it looks OK. Everything else works on the unit (lights, motor, etc) except the sensors (which obviously won't let the door go down).
My question is - what most likely is the cause? Circuit board issue? something else? or do my assumptions above lead to another problem? Hope that all makes sense.
Thanks for your help.
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