Troubleshooting Automatic Washing Machine for no response to power button.

Thread Starter

Baqir

Joined Apr 19, 2020
10
Hello Everyone.
I have an automatic washing machine from Daewoo which recently started showing pressure sensor error but would run after a restart. I ignored the error and eventually it stopped responding on power ON button. On some investigation i found that the power supply circuit is fine and even the microcontroller is receiving power on VDD pin. However, there was no power available on the power switch input line which is coming from the microcontroller. So, i am assuming that the microcontroller is faulty. (Please correct me if my assumption is correct)
I need advice on how to confirm that this is the problem in the circuit. And if only this is the fault in the circuit, how to replace the microcontroller. i think simply changing the device will not suffice because it will need programming also. Will simply changing the IC solve the issue or i have to program it also.
Kindly, help me on this as i am not even able to find a replacement board for this machine. If not repaired, i have to scrap it which i don't want because rest of the machine is absolutely fine.
 

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Thread Starter

Baqir

Joined Apr 19, 2020
10
Hello Everyone.
I have an automatic washing machine from Daewoo which recently started showing pressure sensor error but would run after a restart. I ignored the error and eventually it stopped responding on power ON button. On some investigation i found that the power supply circuit is fine and even the microcontroller is receiving power on VDD pin. However, there was no power available on the power switch input line which is coming from the microcontroller. So, i am assuming that the microcontroller is faulty. (Please correct me if my assumption is correct)
I need advice on how to confirm that this is the problem in the circuit. And if only this is the fault in the circuit, how to replace the microcontroller. i think simply changing the device will not suffice because it will need programming also. Will simply changing the IC solve the issue or i have to program it also.
Kindly, help me on this as i am not even able to find a replacement board for this machine. If not repaired, i have to scrap it which i don't want because rest of the machine is absolutely fine.
1587637239334.png
Here is circuit if anyone is afraid of opening the PDF file attached.
1587637239334.png
 

wayneh

Joined Sep 9, 2010
16,398
... which recently started showing pressure sensor error but would run after a restart. I ignored the error and eventually it stopped responding on power ON button.
I doubt that ignoring it made the sensor error go away. Have you tried to test or replace the sensor? Sometimes a device will be programmed to try several times but then just give up and not try anymore if an error condition is not cleared. I have no idea if this is the case for your washer but it seems worth a try.
 

Thread Starter

Baqir

Joined Apr 19, 2020
10
I doubt that ignoring it made the sensor error go away. Have you tried to test or replace the sensor? Sometimes a device will be programmed to try several times but then just give up and not try anymore if an error condition is not cleared. I have no idea if this is the case for your washer but it seems worth a try.
Thank you Wayneh.
Sounds good! What i was doing while checking the circuit was that i isolated the circuit completely from all the sensors, motors etc and then checked the voltage and continuity. After doing some research on the pressure sensor, i found that in my case the sensor is just simple winding to provide inductance. This inductance changes with increase and decrease of pressure. Now i am thinking that when i removed the sensor altogether, may be the IC was not receiving any signal. And when it was connected, may be as you said, the IC was not responding because the sensor was faulty. You may be right also because i am not seeing any signs of burning on the circuit board.
I will definitely consider your advice and will update you after a try.
 
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