LG MB-387W Service Manual page 23

(TROUBLE 1) The following visual conditions indicate a probable defective control circuit.
1. Incomplete segments.
• Segment missing.
• Partial segment missing.
• Digit flickering (NOTE: Slight flickering is normal.)
2. Colon does not turn on or blink.
3. A distinct change in the brightness of one or more numbers in display.
4. One or more digits in the display are not lighting.
5. Display indicates a number different from one touched, for example, key in 5 and 3 appears in the display.
6. Specific numbers (for example 7 or 9) will not display when key pad is touched.
7. Display does not count down with time blinking or up with clock operation.
8. Display obviously jumps in time while counting down.
9. Display counts down too fast while cooking.
10. Each indicator light does not turn on after setting cooking cycle.
11. Display time of day does not reappear when cooking is finished.
12. Beep sound is not heard when correct key is touched.
CONDITION
1. No input can be
programmed.
2. Some inputs
cannot be
programmed.
3. Display shows a
number or figure
different from one
touched.
4. Random
programming
when touching
other pads.
5. Display is fixed
at some figure
and can not
accept any
input.
CHECK
Check the conn-
ection between
membrane key
assembly and
PCB assembly.
Replace key
membrane
assembly and
check operation.
RESULT
Continuity.
No continuity.
Everything works
as specified.
Still have trouble.
5-13
CAUSE
Defective PCB
assembly.
Loose
connection.
Defective key
membrane
assembly.
Defective PCB
assembly.
REMEDY
Replace PCB
assembly.
Connect them
tightly.
Replace key
membrane
assembly.
Replace PCB
assembly.