Re-Setting Of Microcomputer At Power Failure; Diagnosis Method Of Failure - Sharp SJ-D20N-SLG Service Manual

[3] RE-SETTING OF MICROCOMPUTER AT POWER FAILURE

• At the power failure for over 0.1 second, the control of the microcomputer will be reset.
When the power is re-supplied, the temperature of R-thermistor will be detected again and ON/OFF of the compressor will be decided.
• At the momentary power failure (less than 0.1 second), the protector of the compressor might work due to the high load to the compressor for re-
starting.
• When resetting is made during the operation of the defrost heater, the normal cooling will be resumed.

[4] DIAGNOSIS METHOD OF FAILURE

Check by the following procedure;
1. Disconnect power supply and check the following point.
• Is there any failure portion in inserting connectors?
2. Detach the PWB and check the appearance.
• Is there any burning or abnormal damage?
3. Check the conditions of the fuse and the varistor. (Fuse and varistor are located at the position in the figure.)
• Melting in the fuse cannot be checked visually (as the safer one than transparent glass tube is used). Be sure to detach the connector "CN1"
before measuring the resistance between the both ends of the fuse by the tester.
• Next, measure the resistance value between the both leads of the varistor.
Varistor→
Fuse↓
Flow of excessive current is considerable for some rea-
sons.
Melting
Check for any portion to cause short circuits especially
on the primary circuit.
Fuse and varistor are normal.
Possibility to be caused by excessive current or voltage
Conduction
near the power supply is low. Proceed to the next check
item.
4. Check whether the temperature (resistance value) shown by R-thermistor is correct or not. (Refer to the table below.)
• Detach the connector "CN3" on the PWB and measure the resistance value between 1 and 2 pins.
5. Check whether the temperature (resistance value) shown by Def-thermistor is correct or not. (Refer to the table below.)
• Detach the connector "CN3" on the PWB and measure the resistance value between 3 and 4 pins.
Normal (several hundreds Ω~several KΩ)
Fuse
Varistor
There is a possibility of excessive voltage applied from out-
side with the factor such as thunder etc. When repeated
with a factor other than thunder, there might be the appara-
tus near by generating noises.
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6 – 2
SJD24NSLG
Damage