Samsung ML-6050, Service Manual

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Samsung Electronics 5-37
Troubleshooting
Error code 3-050
Fault
Description
When printer power is on, all lamps on the operator panel blink.
All Lamps Blinking
Model ML-xxxx
Check
1. Harness between the engine and control boards
2. Engine board
Cause
Defective interface between the engine board and control boards (DCU error code ‘78’)
Solution
1. Check the harness between the engine and control boards.
2-1. Check if the engine board works properly when the printer resets. U5 pin 1 should be below 0.7V
for about 122 ms after power is on, then remain over 3.5V.
-Check U5 pin 2 = approx. 3.8V. If so, check R54 or R55.
-Check U5 pin 3 = approx 4V. If so, check R53 or R56, or C35.
-If the voltages are normal, and U5 pin 1 is below 0.7V, replace U5.
-If all are normal, check CPU pin 55. If OK, replace CPU.
2-2. Check for X1 oscillation (6.94407MHz).
2-3. Replace EPROM in the engine board, if defective.
2-4. If all above are OK, replace CPU.
Remark
Others
U4, U202, Q9