Board; Lcd Display Ng - Oki OKIFAX4550 Maintenance Manual

4.3 04W Board

4.3.1 LCD display NG

1: LCD not displayed
Input of pin 27 of IC1
changes from 0V to 5V
upon power on
Yes
6 MHz sine wave is input
between pins 30 and 31
of IC1
Yes
Signal of pin 2 of CN1
changes to 0V or 5V when
the key is pressed
Yes
Pin 1 of CN1
changes to 0V or 5V when
the key is pressed
Yes
Pin 5 of CN1
remains at 0V or 5V upon
completion of copying
Yes
Check CN1 connection.
41309401TH Rev.4
No
Input of pin 4 of IC503
changes from 0V to 5V
upon power on
No
Replace IC502.
No
Replace OSC or IC1.
No
Signal of pin 5 of IC504
changes to 0V or 5V when
No
Replace IC1.
5V is input to pin 4 of
No
Replace IC1.
Yes
Input of pin 5 of IC503
No
comes down to 0V then goes
back to 5V upon completion
of copying
Replace IC504
Replace IC503.
or IC505.
No
the key is pressed
Yes
No
IC504
Yes
Replace IC504.
Yes
Replace IC1.
Check CN1.
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