2-17
EMP-S4
SEIKO EPSON Revision:B
TH Board
The TH Board is attached to the Inner Exhaust Duct to detect the temperature of the lamp
section. To prevent damage to the surrounding components from overheating, the power save
controller on the MA board first provides a warning indication through the temperature
indicator LED, and stops the output of the ballast when the temperature rises above a given
level.
Figure 2-20. TH Board
Safety Switch
This is a backup overheating prevention switch mounted on the side of the Inner Exhaust Duct.
If overheating occurs around the Lamp Assy. due to problems with the exhaust fan, the lamp is
normally turned off by the TH Board to prevent overheating. The Safety Switch is provided as
a backup in case the TH Board and temperature detection circuit fail simultaneously. When the
temperature rises above a given level, the safety switch interrupts AC power to stop all regular
operations. Once the safety switch is activated, power cannot be switched on again until the
temperature falls below the given level.
Figure 2-21. Safety Switch
TH Board
Safety Switch
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