Intermittent Problem Service Check - Lexmark 4227 - Forms Printer B/W Dot-matrix Service Manual

4227-300

Intermittent problem service check

FRU/Symptom
1 The machine
sometimes fails
before POST is
complete.
2-16
Service Manual
Action
Check for the following:
1. Loose connectors. Reconnect all connectors
to the main and sub logic boards.
2. Electrical noise or static discharge.
Check the following items:
• Power supply ground
• Machine frame ground
• Printer interface cable is grounded and
shielded.
3. Intermittently low voltages. Check for ac and
all dc voltages and short-circuits on the main
and sub logic boards.
a. Check the electrical voltage and ensure
that it is within tolerance.
b. Check the continuity of the power
cord.
c. Disconnect the power supply cable
from the connectors CN11 on the
main logic board and CN1 on the sub
logic board. Turn the printer power on
and check all dc output voltages at
CN11 and CN1.
Ensure the output voltages are:
CN11-1 (+40 ±4 V dc) & CN11-3 (GND)
CN11-2 (+40 ±4 V dc) & CN11-3 (GND)
CN11-5 (+5 ±0.5 V dc) & CN11-6 (Signal GND)
CN 1-1 (+40 ±4 V dc) & CN1-3 (GND)
CN 1-2 (+40 ±4 V dc) & CN1-3 (GND)
CN 1-5 (+5 ±0.5 V dc) & CN1-6 (Signal GND)
If the voltages are not correct, replace the
power supply unit.
If the failure remains, replace the main logic
board and sub logic board.
Note: When replacing the main logic board,
always perform the
adjustment" on page 4-3
"Printhead-to-platen gap adjustment" on
page 4-2
.
"Bidirectional print
and the