Toshiba ESTUDIO170F, Service Manual

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e-STUDIO170F Circuit Description January 2005 © TOSHIBA TEC
7 - 34
7.3.7 Toner Empty Detect Circuit
Fig.7-25
The toner empty detect circuit consists of the Engine-CPU (IC37) as the central component. It detects
the amount of toner according to the output signal of the toner empty sensor connected to CN2 on the
Main PBA.
The Engine-CPU causes the TONER_LED signal to go HIGH to turn on IC60. This allows the LED of
the toner empty sensor to emit light. The light is emitted into the toner cartridge through its glass win-
dow. At this time, the light is shut off if toner is present, and reflected by the reflective plate in the toner
cartridge if not. The light detecting element of the toner empty sensor detects the light reflected and
sends a TONER_LEVEL signal to the Engine-CPU.
The TONER_LEVEL signal goes HIGH if toner is present, and LOW if not. This detect operation is
repeated. When the time for which the Toner signal is at Low level exceeds a certain time and the Low
level count happens more than five times, a toner near empty state will be assumed. After that, when
the time for which the signal is at Low level becomes longer and the detected count exceeds five times,
a toner empty state will be assumed.
Signal Name Type Active Description Destination
TONER_LED O H Toner empty sensor LED signal IC60
TONER_LEVEL I - Toner empty sensor output signal Toner empty
sensor
Main PBA
Toner empty
sensor
TONER_LED
TONER_LEVEL
88
98
2
12
8
3 5
CN2
IC37
Engine-CPU
IC60
PG