5.5. Inverter power supply (U)
DO NOT try to REPAIR H.V. Inverter power supply (U).
Replace complete H.V. Inverter(U) Unit.
WARNING: HIGH VOLTAGE
Test if failure codes H95, H97 or H98 appear when performing
the following procedure. It is recommended to use an AC line
input current ammeter for testing.
Test 1
1. With the oven unit’s AC power supply cord is unplugged
from the wall outlet, unplug the 2 pin H.V. connector CN703
from the magnetron tube.
2. Place 1 liter of water load into oven cavity.
3. Plug in the oven’s AC power supply cord into outlet.
4. Program DPC.
a. Press Clock pad once.
b. Press Timer pad once.
c. Press Start pad once.
d. Press Power Level pad once.
5. Program oven at High power for 1 minute and press [Start]
pad.
a. After approximately 37 seconds, oven stops operating.
b. During
oven
operation,
the
input
current
is
approximately 0.5 to 1A. If both a and b are OK,
proceed to test 2.
INPUT CURRENT
FAILURE CODE
Unplug CN703
0.5 to 1A
Oven stops in 37
seconds after started.
Test 2
Continued from Test 1
1. Unplug the oven’s AC power supply cord from outlet.
2. Unplug 3 pin connector CN701. CN703 remains unplugged.
3. Plug in the oven’s AC power supply cord into outlet.
4. Program DPC.
a. Press Clock pad once.
b. Press Timer pad once.
c. Press Start pad once.
d. Press Power Level pad once.
5. Program oven at High power for 1 minute and press [Start]
pad.
a. After approximately 3 seconds, oven stops operating.
b. During
oven
operation,
the
input
current
is
approximately 0.4A.
INPUT CURRENT
FAILURE CODE
Unplug CN701
0.4A
Oven stops in 3
seconds after started.
If both a and b check OK, the Inverter Power Supply (U) can be
determined to be OK.
5.6. Temperature thermistor
These sensor monitors the heat produced by the heater circuit
and maintains the magnetron temperature which user had
selected. Normal room temperature 10°C to 30°C, the reading
across the temperature thermistor should be as follows.
TEMP
MAGNETRON THERMISTOR
100°C
30-60K
Ω
25°C
700K-1.5M
Ω
If the resistance reading is out of the range stated here, the
thermistor is detective and must be replaced.
15
NN-SD798S / NN-ST778S / NN-SA768W
Summary of Contents for NN-SA768W
Page 2: ...2 NN SD798S NN ST778S NN SA768W ...
Page 3: ...3 NN SD798S NN ST778S NN SA768W ...
Page 5: ...1 SCHEMATIC DIAGRAM 5 NN SD798S NN ST778S NN SA768W ...
Page 23: ...8 6 How to check the semiconductors using an OHM meter 23 NN SD798S NN ST778S NN SA768W ...
Page 24: ...9 EXPLODED VIEW AND PARTS LIST 9 1 EXPLODED VIEW 24 NN SD798S NN ST778S NN SA768W ...
Page 33: ...10 DIGITAL PROGRAMMER CIRCUIT 10 1 NN SD778S 33 NN SD798S NN ST778S NN SA768W ...
Page 34: ...34 NN SD798S NN ST778S NN SA768W ...
Page 35: ...10 2 NN ST778S 35 NN SD798S NN ST778S NN SA768W ...
Page 36: ...36 NN SD798S NN ST778S NN SA768W ...
Page 37: ...10 3 NN SA768W 37 NN SD798S NN ST778S NN SA768W ...
