Dell GCR-8481B Service Manual page 5

3. Troubleshooting Guide
A. LED doesn't light.
Check Power Voltage
(TP1:3.3V, TP20:2.5V, TP2:12V)
Reference Voltage
[TP3:DVC(1.35V) and GND.]
OK
Does "H" output in IC501
pin ?
109
YES
Check and replace R705,
R706, Q701 and LED701.
A-1
Is the CLOCK Frequency
of IC501 pin 33.86MHz?
171
YES
Check and replace IC501.
22
NG
Check the power input
pattern.
NO
Is the CLOCK Frequency of
IC501 pin 33.86MHz?
171
YES
Check IC501.
Check and replace
NO
X501; 33.86MHz,
X502: 40MHz
NO
A-1