AC Voltage Protector Repaired
AC Electronic protector can be found in all around the world. This is a local brand machine and the functions of electronic protector are:
1- Within the first 5 minute after plugin the AC cord of the machine to the AC outlet, there was no output voltages and the Red power LED will be On.
2- During this time the circuit starts to check the incoming AC voltage and the range should not lower than 185V and not more than 245V.
3- If the AC voltage is within range the Green power LED will turn ON and there will be output voltage.
4- This checking is continuous and in any seconds if the incoming voltage is too high or too low than the rated specification, then it will cut off the output voltage thus protecting the electrical devices connected to it.
This device is most useful when an area electricity is cut off and suddenly it was restored or if there is a frequent Off and On due to instability of the AC source . The initial incoming surge AC voltage if not block it would cause serious problem to our home electrical/electronics devices.
The complaint of this protector was that it can’t function. This means it has input but no output voltage.
As you can see from the photo above there are not many components installed on the circuit board so I had decided to repair it by using the Eliminating method.
With this method one must check all the components one by one till you find the bad component. The tools that I used in this test were the analogue and digital multimeter, ESR METER and digital capacitance meter.
In the above circuit, I have tested all the resistors, diodes, caps as well as relay and all of them passed the test successfully except one resistor and the value was 1 Mega Ohm ( Brown, Black Green and Gold). It reads 1.623 M Ohm. After the replacement with a new resistor the protector refuses to work. For your information the only component that I did not test was the Op-amp 14 pins DBL324 IC. I believe this IC is bad also and need replacement since a new resistor did not restore the unit. Since I can’t find one in my spare parts compartment I looked up to Google for an answer. From the information I had gathered this IC part number is more or less the same function as LM324N (National brand).
After the replacement was done I turned the machine On and it worked but not for long. After sometimes the IC failed again. I decided to replace it with original part number and guess what? It worked like a charm!
This article was prepared for you by Mr Beh, one of our ‘Master Authors’ from Iran.
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