Panasonic KX-MB771GR Service Manual page 38

KX-MB771GR
6.9.2. RIGHT SIDE FAN (FAN2)
When the output of pin D11of IC300 becomes high level or pulse, Right side FAN (FAN2) is activated.
During the FAN rotation, the pulse signal is output from pin 2 of FAN2 and input to pin W24 of IC300.
When this pulse is stopped, it is judged that FAN error occurred.
6.9.3. FAN CONTROL
This unit is equipped with two FANs to prevent the developing devices from overheating during printing.
The FAN rotates at high speed (Approx. 3000rpm) while printing (controlling the developing devices).
After printing is finished, FAN rotates at low speed (Approx.2200rpm) while predetermined period.
1. Full speed control
To rotate the FANs with full speed, constant high level are output from A11 and D11 of IC300. Then Q512/Q510 and Q519/
Q520 are all turned on. So 24V are output from collectors of Q510 and Q520. Since each FAN consumes approx. 0.1A,
approx. 4V is reduced through R525 and R530. Then approx. 20V are supplied to each FANs.
2. Half speed control
To rotate the FANs with half speed, pulse signals are output from A11 and D11 of IC300. Then all Q512/Q510 and Q519/Q520
repeat ON and OFF according to the pulse duty (30KHz/12.5%). These pulses are integrated by R525/C515 and R530/C518
and converted to DC voltage. So approx. 12V are supplied to each FANs.
Pin No. Level
High
IC300 A11
Pulse
Low
High
IC300 D11
Pulse
Low
FAN operation mode
Left side FAN Full speed
Left side FAN halfl speed
Left side FAN stop
Right side FAN Full speed
Right side FAN Half speed
Right side FAN stop
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