KD -120-12 Power Supply Repaired (Replaced Few Bad Components)
I received this power supply for repair.
The owner of the machine told me this accident has happened:
While he was giving water to plants, water was spilled on this power supply and caused not working any more. This power supply was the source of energy for the LED S that is giving light for growing the plants. I started to repair it.
The cover opened by two screws. Inside the machine was a button that by rotating one can set the entrance voltage from 110 to 220v and set voltages.
This is a SMPS power supply and all the major component of such design were present on pcb such as transformers, Schottky diode regulator ic, and so on… by looking I just found 1 watt resistor with this color coding red, red, gold, gold bands this is a 2.2 ohms 5% and ½ watt .
The color bands over this resistor was cracked and showed something happened for it and yes it was opened circuit. Near to this resistor there were two big transistors that I decided to check them too.
My multi meter proved that these transistors were shorted D13007K. The rest of the semiconductors and other components were found good. I replaced all bad components and started to turn on this machine. Before I restart the machine with the wires of 220 volt I install 100-watt lamp in the place of entrance fuse to test and see if there are more shorted components in the machine or not? The lamp just blinked in a second and then turned off this means no more shorted components in the circuit exist.
Then I powered up the machine and I received 12 DC volts in output s and the machine returned to service again.
Note 1: In this repair I just used the ohm check method and ATLAS DC 75 was proved all the multimeter founding’s and was helpful too. And also Blue Ring tester confirmed that the transformer was good and the repair of the machine was reasonable and economical and the cost was only 50 cents.
NOTE 2: I also replaced the weak green power indicator LED to a stronger red one.
Note 3: Let me tell you that the 5-amp fuse was intact and showed that this fuse installed just for any entrance AC over amperage and does not care about any shortage inside the circuit actually this machine does not have any protection component against any internal short circuit-bad design.
This article was prepared for you by Mr Beh from Iran
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