The CPU monitors the temperature around the optics cavity through a
thermistor which is under the left scale. When the detected temperature
reaches a certain threshold value (see the following table), the optics cooling
fan(s) on the rear of the optics side plate starts to draw cool air into the
optics cavity. The hot air exits through the vents in the upper cover. The
fan(s) operate until the temperature drops below the threshold temperature.
Note that the A153/155/156 models have two fans; this is because the
exposure lamp is more powerful in this model, so more cooling is needed.
A153/A155/A156 A157/A159/A160
Rotating temperature
45
°
C40
°
C
Number of fans
21
The thermofuse (located on the 1st scanner) provides back-up overheat
protection. It opens at 121
°
C and removes ac power to the exposure lamp.
The thermofuse is not resettable.
An optics anti-condensation heater is available as optional equipment (it is
also a service part). To prevent moisture from forming on the optics, it turns
on while the main switch is turned off.
The main board controls the exposure lamp voltage through the ac drive
board. The exposure lamp voltage is based on the base lamp voltage (set by
SP4-001) and various correction factors. The corrections depend on whether
the image density is manually selected or whether ADS mode is selected.
For details, see Process Control - Summary.
A156/A160/A162 2-40 STM
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