SHARP SP1647 Technical Report

Date: Dec. 2, 1993

COPIER : SF-2022

TROUBLESHOOTING WHEN THE COUNTER FAILS TO REGISTER.

(TOTAL COUNTER, MAINTENANCE COUNTER, DEVELOPER COUNTER, ETC.)

1.Model name: SF-2022 / 2027

2.General: When the main power is turned off, the POFA signal is not output, and the counter

signal is sometimes not sent to the EEPROM (the counter doesn’t register) because the
CPU can’t detect the power cutoff. To remedy the above problem the Q103 transistor
and R123 resistor of the POFA circuits have been changed.

No. : SP-1647

3.Cause: Due to efficiency fluctuations in the Q103 transistor and the IC133 in the POFA signal
generation circuits, the output saturation voltage is high, and when the cut off voltage of
the Q103 transistor is low, the Q103 does not always completely cut off when the main
power is turned off.

4.Description: The detection level is raised and the output saturation voltage is lowered by raising the
R123 resistance and decreasing the current (I1). By changing the R123, the Q103 input
voltage (base voltage) decreases, and therefore the Q103 internal resistance changes,
and the Q103 input voltage is adjusted to the Q103 voltage level before the R123
change.

SHARP CORPORATION Reprography Division

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