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30 April, '89
5. Optics Cooling Fan
prevent hot air from building up in
To
the optics cavity, the cooling fan
blows in cool air from outside. This
fan is energized by two thermo-
switches: TS1 and TS-3. TS-1 is un-
der the exposure glass (115 volt units)
or near the lens home position sensor
(220/240 volt units), and TS-3 is be-
side the cleaning unit.
These two thermoswitches operate as
follows:
Optics Thermoswitch
-
ON
O F F 4 5 ° C
-
Cleaning Thermoswitch (TS-3)
-
ON
OFF 40°C
-
6. Anticondensation Heater
When the main switch is off, 100
volts ac is applied to the anticondensa-
tion heater circuit through RA106. If
TS-2
is
on,
heater circuit turns on.
When the main switch is on, RA106
energizes; the anticondensation heater
circuit
i s t h e n c o n t r o l l e d t h r o u g h
SSR-9 on the ac drive board.
TS-2 closes the circuit at 17°C and
opens it at 25° C.
An internal thermofuse guards against
overheating.
It opens at 169°C.
(TS-1)
55°C
55°C
the
anticondensation
2-16
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