Digital Programmer Circuit - Panasonic NN-E251W Service Manual

9.4 (TROUBLE 4) Trouble related to digital programmer circuit
SYMPTIOM
No display when oven is first
plugged in
SYMPTIOM
No key input.
No beep sound.
Power relay A(RY-2) does not
turn on even though the
program has been set and the
start pad is tapped.
No microwave oscillation at
any power setting.
Dark or unclear display.
Missing or lighting of
unnecessary segment.
How to check the semiconductors using an ohmmeter
Diode
Transistor
NPN Transistor
PNP T
Digital Transistor
NPN
Transistor
E C B
Digital Transistor
PNP Transistor
E C B
STEP
1 Low voltage transfrmer (LVT)
2 IC-1 pin 42 voltage
3 IC-1 pin 10 voltage
(14 pin of IC-2).
STEP
1 Membrane switch continuity.
1 IC-1 pin 34 voltage.
1 IC-1 pin 40 voltage while operation.
1 IC-1 pin 8 voltage while operation
at high power.
1 Replace display and check operation.
1 Q1~Q7 check operation.
2 Replace IC-1 and check operation.
A
(CATHODE)
(ANODE)
A
C
(COLLECTOR)
TZTA - -- --
B
(BASE)
E
ECB
(EMITTER)
ransistor
TZTC - - --
B
ECB
E
B
A110
C
E
B
C106
C
CHECK
secondary voltage
CHECK
K
K
E
C
15
RESULT CAUSE/CORRECTIONS
Abnormal 0V
Normal
Abnormal
Normal=5V
Abnormal
Normal IC-1, CR1,Q6,Q7
RESULT CAUSE/CORRECTIONS
Abnormal Membrane switch
Normal
Abnormal
Normal
Abnormal
Normal=5V RY2, Q11, D4
Abnormal
Normal=5V RY1, Q10, D3
Normal
Abnormal
Normal
Abnormal
Normal
Abnormal
FORWARD
A-K SMALL
FORWARD
B-E SMALL
B-C SMALL
∞
C-E
FORWARD
E-B SMALL
C-B SMALL
∞
C-E
FORWARD
E-B SMALL
C-B SMALL
∞
C-E
FORWARD
E-B 10KΩ-90KΩ
C-B SMALL
∞
C-E
LVT
Step 2
VL 1
Step 3
ZD1, Q8
DISPLAY
IC-1
IC-1
Q12, BZ1
IC-1
IC-1
DISPLAY
IC-1
Step 2
Q1~Q7
IC-1
DISPLAY
REVERSE
∞
REVERSE
∞
∞
∞
REVERSE
∞
∞
∞
REVERSE
∞
∞
∞
REVERSE
10KΩ-90KΩ
∞
SMALL