Philips NN-SN968B, Servise Manual

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5.4. 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 button once.
d. Press Power Level pad once.
5. Program oven at High power for 1 minute and press [Start]
button.
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 button once.
d. Press Power Level pad once.
5. Program oven at High power for 1 minute and press [Start]
button.
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.
5.5. 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 35K
Ω
to 110K
Ω
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.
1. Program the DPC into TEST MODE (Plug-in oven
→
press
Clock pad once → press Timer pad once → press
Start button once → press Power Level pad once).
2. Program oven at Standing Time for 1 minute and press
[Start] pad.
3. Press Power Level once, the thermistor level reading will
shown on the display.
The normal reading should be in the range of 16-230.
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NN-SN968B / NN-SN968BT