Panasonic NN-T259WB, Service Manual

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21
Trouble Related to Digital Programmer Circuit
How to Check the Semiconductors Using an OHM Meter
SYMPTOM STEP CHECK RESULT CAUSE/CORRECTIONS
No display when oven is first
plugged in.
Oven is dead.
1 Fuse pattern of DPC Normal STEP 2
Open (NOTE) Shorted Circuit of ZNR, L.V.T., Oven Lamp etc. Replace DPC
2 IC10 Pin 9
(12V line) Abnormal 0V IC10
Normal 12V Step 3
3 IC-1 Pin 16 voltage
(Emitter of Q10) Abnormal ZD10, Q10, Ribbon Cable
Normal = 5V Step 4
4 IC-1 pin 10 voltage
(15 pin of IC220)
Abnormal IC-220
Normal IC-1, CX1
NOTE
Procedure of fuse pattern repairing is as follows:
1. When the fuse pattern (PF2) opens.
(1) Remove the jumper wire (PF3).
(2) Insert the removed jumper wire (PF3) to “(PF2)” position and solder it. If both “PF2” and “PF3” fuse patterns are open, please replace DPC.
NOTE: * At the time of these repairs, make visual inspection of the varistor for burning damage and examine the transformer with tester for the
presence of layer short-circuit (check primary coil resistance).
If any abnormal condition is detected, replace the defective parts.
SYMPTOM STEP CHECK RESULT CAUSE/CORRECTIONS
No key input 1 Push button switch Abnormal Push button switch
Normal IC-1
No beep sound 1 IC-1 pin 8, voltage Abnormal IC-1
Normal IC220, BZ310
Power relay A(RY-2) does not turn on even
though the program has been set and the start
pad is tapped. 1 IC-1 pin 11 voltage while operation Abnormal IC-1
Normal = 5V Step 2
2 Short circuit between pin 6 and pin 16
of IC-2 Still not turn on RY-2
RY-2 turns on IC-220
No microwave oscillation at any power setting. 1 IC-1 pin 7 and 72 voltages while oper-
ation at high power Abnormal IC-1
Normal
7---5V, 72---5V Step 2
2 Q220 transistor Abnormal Q220
Normal IC220
Dark or unclear display 1 Replace display and check operation Normal DISPLAY
Abnormal IC-1
Missing or lighting of unnecessary segment 1 Replace IC-1 and check operation Normal IC-1
Abnormal DISPLAY
Oven shuts down on Micropower after a short
time (set in test mode) (set high power 1 Min)
H97/H98 appears in window and oven stops
operation. Program High power for 1 minute
and conduct following test quickly, unless
H97/H98 appears and oven stops. 1 Unplug CN702 (2 pin) connector and
measure voltage between terminals 0V 1. Latch switch
2. DPC/Power relay
AC line voltage of 240V Step 2
2 Unplug CN701 (3 pin) connector and
measure pin 1 voltage 0V 1. DPC
Approx. AV 3V 1. Magnetron
2. Inverter
NEW H.V.
Diode
A K
Transistor
C
B
E
NPN Transistor
2SC-----
2SD-----
ECB
Digital Transistor
PNP Transistor
E C B
(ANODE)
(CATHODE)
E
C
B
ECB
(EMITTER)
(BASE)
(COLLECTOR)
A
K
2SA-----
2SB-----
PNP Transistor
E
C
B
FORWARD REVERSE
A-K SMALL
FORWARD REVERSE
B-E SMALL
B-C SMALL
C-E
FORWARD REVERSE
E-B SMALL
C-B SMALL
C-E
FORWARD REVERSE
E-B 10k
Ω
~30k
Ω
10k
Ω
~30k
Ω
C-B 50k
Ω
~90k
Ω
C-E 40k
Ω
~80k
Ω