Panasonic UF-490 Service Manual page 101

4.6.2. Poor Transmitted Copy Quality
START
Make a copy.
Is the printed copy
normal?
Yes
Perform a transmission
test to a reference
fax unit.
Is the transmitted
copy normal?
Yes
Does poor transmitted
copy appear only
when transmitting to a
specific receiver?
Yes
The receiving unit
may be defective.
END
No
Is the CIS LED
lit?
Yes
Is CN3 on the
SC PCB
connected properly?
Yes
(1) Replace the CIS.
(2) Replace the SC PCB.
No
Check the Telephone Line Cable.
Replace the SC PCB.
No
Telephone line quality
is poor.
Does CN3, pin 7 on
No
SC PCB measure
+24 VDC?
Yes
Does CN3, pin 6
measure 0V when
the scan starts?
Yes
Replace the CIS.
No
Connect it correctly.
101
No
Replace the Low
Voltage Power
Supply Unit.
No
Replace the SC
PCB.