Panasonic KX-MB2230JT Service Manual page 57

6.9.6.1. FAN motor Lock detect and protection
When FAN motor is locked, motor current becomes much more than normal condition.
So the voltage between R616 becomes bigger than normal condition, and this causes Q606 turns on.
After turning on of Q606, the base voltage of Q608 rises gradually due to the integration effect of R634, R628 and C616.
If FAN motor lock condition continues over 4 seconds, base voltage of Q608 reaches to 0.7V, and Q608 turns on.
Once Q608 turns on, Q610 and Q609 turns on consequently.
By turning on of Q609, input level of IC504_pin2 becomes less than 0.4V and Q607 is turned off.
Therefore no current is supplied to FAN motor.
Due to the turning off of Q607, Q606 is turned off accordingly.
But the combination of Q610 and Q608 keep the on condition of Q608 even after turning off of Q606.
As the result after approx. 4 seconds of FAN motor lock, no current is supplied to FAN motor.
At the same time when Q608 is turned on, FANDET1 signal (IC300_pinAE23) becomes from "H" to "L".
By checking FANDET1 signal, IC300 recognizes that FAN error occurred.
This condition is maintained until FAN motor lock condition is eliminated and power off/on of machine.
6.9.6.2. Extra low current detection
When connector insertion is insufficient or FAN/FAN lead broken, no current flows to the FAN motor.
In the normal condition, since current flows through R616, Q603 turns on.
During Q603 on condition, Q603 does not affect Q606 operation.
But when current does not flows through R616, Q603 turns off.
Once Q603 turns off, base current of Q606 flows through R626 and R627, then Q606 turns on.
The sequence after turning on of Q606 is same as described in FAN motor Lock detect and protection.
After approx. 4 seconds Q606, Q608, Q609 and Q610 are all turn on, consequently FANDET1 signal becomes "L".
By checking FANDET1 signal, IC300 recognizes that FAN error occurred.
This condition is maintained until FAN becomes normal condition and power off/on of machine.
KX-MB2230JT/ KX-MB2270JT/ KX-MB2515JT/ KX-MB2545JT/ KX-MB2575JT/ DP-MB310JT
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