Panasonic KX-MB771GR Service Manual page 47

6.12.9. TONER SENSOR.... "TONER EMPTY", "TONER LOW", "CHANGE DRUM"
The Sensor detects whether or not the Drum unit and the toner are present.
When there is not Drum unit, Hall IC (IC50) turns off, and the input signal of IC300-AE22pin (Main Board) becomes a High level
over 9s. When the Drum unit is set, Hall IC (IC50) turns ON/OFF. If the time of IC300-AE22pin's Low level is under 600ms, there
is enough toner in Drum unit, if not, toner is near empty.
Toner Sensor
The rest of toner is detected by the move speed of the magnet put on the pendulum of Mixing Paddle. The pendulum is pushed
up by the Mixing Paddle, then it falls down by its own weight. The rotation speed of paddle is set slower than the one of pendu-
lum which falls down by its own weight. When the toner is still left, the pendulum falls and stops on the toner, then pushed by the
paddle, it starts to rotate. When no toner is left, the pendulum falls to the bottom. Consequently the contact time between the
magnet and Hall IC becomes short when toner is left and long with no toner.
State
Toner Set (full)
Near Empty Toner
Mixing Paddle does not rotate
("CHANGE DRUM")
Display
-
TONER LOW
CHANGE DRUM
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Signal (IC300-AE22pin)
level = about 0.3s
Low level>1s
High level fix or Low level fix
KX-MB771GR