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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.
For SD452W model
a. Press Clock
button once.
b. Press Timer
button once.
c. Press Start
button once.
d. Press 1000W/600W
button once.
For ST462M & ST452W models
a. Press Timer
pad twice.
b. Press Start
pad once.
c. Press Micro Power
pad once.
5. Program oven at High power for 1 minute and press [Start]
pad.
a. After approximately 23 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 23
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.
For SD452W model
a. Press Clock
button once.
b. Press Timer
button once.
c. Press Start
button once.
d. Press 1000W/600W
button once.
For ST462M & ST452W models
a. Press Timer
pad twice.
b. Press Start
pad once.
c. Press Micro Power
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
The thermistor that is attached to the magnetron detects the
temperature of the magnetron and will stop magnetron
operation when overheating is detected. A normal thermistor´s
resistance is 35KΩ to 110KΩ for an ambient temperature range
of 10-30 degree C.
If the resistance reading is out of the range stated here, the
thermistor is detective and must be replaced.
It is also possible to display thermistor level by taking the
following steps.
For SD452W model
1. Program the DPC into TEST MODE (Plug-in oven → press
Clock
button once → press Timer button once → press
Start
button once → press 1000W/600W button once).
2. Program oven at Standing Time for 1 minute and press
[Start] button.
3. Press Sensor Reheat
once, the thermistor level reading
will shown on the display.
The normal reading should be in the range of 16-230.
For ST462M & ST452W models
1. Program the DPC into TEST MODE (Plug-in oven → press
Timer
pad twice → press Start pad once → press
Micro Power
pad once).
2. Program oven at Standing Time for 1 minute and press
[Start] pad.
3. Press Reheat
twice, the thermistor level reading will
shown on the display.
The normal reading should be in the range of 16-230.
16
NN-SD452W / NN-ST462M / NN-ST452W