DOWNLOAD Panasonic KX-MB1500UCB Service Manual ↓ Size: 16.3 MB | Pages: 127 in PDF or view online for FREE

33

KX-MB1500UCB

1. Timing chart

2. Wave form

PHA1

Pin4 of
IC502

Motor 
current*

Fig. 2

*Motor current is changed according to the scan speed.

5V/Div

10V/Div

0.5A/Div

34

KX-MB1500UCB

1. Timing chart

2. Wave form

PHA1

Motor 
current

Pin4 of
IC502 or
IC700

Fig. 3

Motor current is changed according to the scan speed.

㪌㪭㪆㪛㫀㫍

㪉㪇㪭㪆㪛㫀㫍

㪇㪅㪌㪘㪆㪛㫀㫍

35

KX-MB1500UCB

This unit is equipped with FAN motor to prevent the developing devices, Power Supply Unit (PSU) and other devices from overheat-
ing during printing.
The FAN rotates at high speed (Approx. 4000rpm) while printing.
After printing is finished, FAN rotates at low speed (Approx.1700rpm) while predetermined period.

FAN drive circuit consists of 2 blocks.
One is "Speed control Block" and the other is "Abnormal detect and Rock protect Block".

For the control of FAN speed, comparator IC (IC504) is used. 
This IC compares (+) side input level and (-) side input level.
If (+) side input level is bigger than (-) side input level, output of this IC is "OPEN".
If (+) side input level is less than (-) side input level, it outputs "L" level.

In half speed mode, IC300_pinA11 outputs pulse (frequency is about 30KHz, duty is about 37.5%).
This pulse is integrated by R644 and C618 then IC504_pin2 becomes approx. DC1.24V. Input level of IC504_pin3 is determined by
the voltage of between R624.
If voltage between R624 is less than 1.24V, output of IC504_pin1 becomes "H".
Then Q607 is turned on. So voltage between R624 (=the voltage of IC504_pin3) rises gradually.
When the voltage between R624 exceeds 1.24V, output of IC504_pin1 becomes "L".
Then Q607 is turned off. So voltage between R624 falls gradually.
By repeating these sequence, voltage between R624 is controlled approx. 1.24V.
On the other hand, if FAN voltage is represented Vo and voltage between R624 is represented VL, VL is determined as below for-

mula.

VL=Vo*R624/(R623+R624) 

→ Vo=VL*(R623+R624)/R624

Since each values are as follows, Vo is determined approx. 9.7(V).

VL=1.24(V), R623=150(K ohm), R624=22(K ohm)
Vo=1.24*(150K+22K)/22K=9.7(V)

Therefore by reducing the FAN power supply voltage, FAN rotates with half speed.

36

KX-MB1500UCB

In full speed mode, IC300_pinA11 outputs constant 3.3V.
When 607 is turned on, Vo becomes approx. 22V (approx. 2V drops between R616).
So the voltage between R624 is determined as follows.

VL=Vo*R623/(R623+R624)=22*22K/(150K+22K)=2.8(V)

Since IC504_pin2 is 3.3V and IC504_pin2 is 2.8V, IC504_pin1 is always "H". 
Consequently Q607 is always turned on, then approx. 22V is supplied to FAN motor.
 Therefore FAN rotates with full speed.

When IC300_pinA11 is "L", Q607 is turned off, then FAN motor stops rotation.

FANON1 

(IC300_pinA11)

FAN Operation mode

H

Full speed

Pulse

Half speed

L

Stop