Ricoh FT7770 Service Manual page 483

30 April, '89
ELECTRICAL OPERATION
The bin copy sensors (upper and lower) detect copy paper in the bins. The
jam sensors (upper and lower) check that copy paper is fed to the bins and
also count copies as they enter the bins.
The circuit description for all four sensors is the same (except for connector
numbers and pin numbers).
circuit (shown above).
When there is no paper in the sorter bins, LED-270 on the sensor LED board
activates PH1.
than pin 11.
IC203 pin 13 then goes LOW.
pin 11, causing pin 13 of IC201 to output HIGH. Pin 11 of IC202 is then
higher than pin 10; so, IC202 pin 13 goes HIGH. This HIGH signal at CN112-A8
informs the sorter main board that no paper is present.
When paper enters a bin, the phototransistor (PH1) turns off. This causes the
circuit to output a LOW signal to CN112-A8. The sorter main board determines
that paper is in the bins.
So, we will discuss only the upper bin copy sensor
PH1 turns on Q254, which causes IC203 pin 10 to be greater
IC201 pin 10 is then lower than
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