Service manual

25
Troubleshooting
Trouble 1: The following visual conditions indicate a probable failed control circuit.
1. Incomplete segments.
 Segment missing.
 Partial segment missing.
 Digit  (Note: Slight  is normal.)
2. 
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 dify.
6.  numbers (for example 7 or 9) will not display when  pad is touched.
7. 
8. Display obviously jumps in time while counting down.
9. 
10. 
11. Display time of day does not reappear when  is 
CONDITION CHECK RESULT CAUSE REMEDY
Everything works
Continuity.
No continuity.
Still have trouble.
Defective key
membrane
assembly.
Defective PCB
assembly.
Loose
connection.
Defective PCB
assembly.
Replace key
membrane
assembly.
Replace PCB
assembly.
Connect them
tightly.
Replace PCB
assembly.
Replace key
membrane
assembly and
check operation.
Check the conn-
ection between
membrane key
assembly and
PCB assembly.
2. Some inputs
cannot be
programmed.
1. No input can be
programmed.
3. Display shows a
num
e
e
touched.
4. Random
programming
when touching
other pads.
and can not
accept any
input.