NEC PA723U User Manual page 173

7. Maintenance
To clear the lamp usage hours:
1. Place the projector where you use it.
2. Plug the power cord into the wall outlet, and then turn on the projector.
3. Clear the lamp usage hours.
From the menu, select [RESET] → [CLEAR LAMP HOURS] and reset the lamp usage hours. (→ page 134)
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