There are two miniature SMD LEDs. One is clear and one is yellow. Unsolder the YELLOW colored LED. Replace with another high intensity SMD LED. The anode (+) is marked on the circuit board and is located away from the infrared receiver side.

SMD LEDs are difficult to find as a spare part. You can carefully ground down a normal sized LED with a Dremil until it is the correct fit.

Reassemble the Apple TV following the reverse of these to steps used to disassemble it.