[Mark McLeod]

I agree with rwaliany's suggestion to test each of your IR sensors.

In addition to the method suggested you can also test each sensor by using one of the regular digital inputs and printf'ing the value. With a working sensor you will see a stream of 1's & 0's when the beacon is on.

[edit]
(I got chased out of the building partway through answering your post last night - need a smiley with z's)

Good practice is to test the components at each stage of construction.
- Unadulterated IR sensor
- After soldering wires to sensor
- After mounting in tube
- On servo
- Full system

Handle the sensors carefully. They are susceptible to static electricity, overheating from soldering/heat guns, incorrect wiring, being knocked around, etc. Only plug them in to a powered down controller and double check your connections on all leads from the sensor to the controller before urning it on.