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I have this power supply ps24e it is from Aiphone. made in Japan. it has 24 volt 2 ampere. it is not powering on. let's check it when you are testing any device, always use series lamp to power up and if you don't have a good practical experience in Power Electronics, never try to repair it yourself DC voltage positive negative and ground we don't have any output here while we have 238 volts AC input, let's see what is the problem. for troubleshooting we will open it, it have four screws here, one two three and four and this is covered yes it have some discoloration let's open it and never touch any area before testing the voltage on Main DC capacitor, DC voltage okay it is discharged it is safe. now let's inspect it we can see we have burning sign here on this canister wow this IC is damaged we can see and it is using 3842 ic so this family 3842, 3843. 3844 & 3845 ICs these ices have approximately the same circuit and this resistor is burned out this resistor this capacitor, maybe this capacitor have burning sign from this IC initially we find IC and this resistor other components are looking some good now we will replace this IC. locate the cut mark this is index marks that is pin number one first I will touch the solder to all pins so that it is better for thermal conductivity we can see one pin is separated totally yes this is 3842 and this one is if you have uc3842 are ka3842 the same, both numbers are the same you can use any one number. 3842 this is the generic number now by checking the cut Mark index Mark aligning pin 1 to pin 1 on the footprint install this IC here in the board. I will bend one pin here so that it will hold in the board after soldering using isopropyl alcohol, technical alcohol, thinner, methylated spirits we will use for cleaning the soldering area now we will check this capacitor why it is looking in suspected condition let's check it discharge the capacitor properly before testing, before connecting to multimeter red test lead too positive and black test lead to ground it is 36.8 micro farad and it is 47 so its value is decreased we will replace this capacitor, because it must be 47 microfarads. if you will install in this condition it will not hold the charge properly and power supply will go in fluctuation because it will not maintain the voltage on VCC pin. I have this capacitor for 47 micro 50 volt discharge it and then check it it 45.5 it is good because this one. it was 36 but this one is good we can check this rectifier. it is also damaged now I will remove it I will use 1N4007 diode in the auxiliary section insert the diode by taking care for the polarity this resistor that is here we will open one end, 5.3 ohms. this is connected here and it is going to drive the mosfet yes it is connected at pin number six then here, then it is reaching to mosfet. so resistor is good might be it is damaged due to this IC or we need to verify this mosfet now I am installing the capacitor, when you are installing polar capacitor, DC capacitor take care for the polarity. never connect in Reverse plurality, otherwise the capacitor will damage immediately. if you are searching for the schematic, maybe you will not find the exact circuit diagram. for that purpose check the IC number and go to Google and search for the datasheet for that ic. in the datasheet you will find sample circuit for this IC it will guide us how this circuit is working. now let's check it what is the result now have some strange sound and if you check voltage we have low voltage fluctuation that means the IC is switching now but it have something short circuit in the secondary and we can also monitor at the IC pin number five and pin number seven number eight we can see the IC have fluctuation if we want to find the fluctuation the best way we can open the output rectifier that is the easiest solution. this time we have low voltage with fluctuation that means there is something short circuit, if we have full Voltage here more than the rated value with fluctuation that means the feedback network is problematic but now we have output voltage in millivolts and we have fluctuation so we need to check the voltage here and we can also check here on the rectifiers we can see there is something wrong in the output side so we need to verify here let's check output side components set multimeter to diode this diode the zener diode is damaged this zener diode is also damaged. yes this SCR that is also damaged here we have TL431 voltage reference and behind this we have SCR so scr is damaged, we have this zener and both zeners are short circuit, let's remove it and then we will check it now I am removing the short circuit components Short Circuit now I am removing the SCR is damaged now i am removing this zener now I removed this zener diode C27 27 volt zener, yes it is short circuit it is using two TL431A in this circuit after removing these components let's power on and check either there is a short circuit present or finished now. DC voltage 45 volts we can see we have 45 volt here. it is now uncontrolled there is no feedback if we check voltage at optocoupler input side, that means the feedback is reaching here and if we check here it have 3.5 volt that's not good that means our optocoupler is might be damaged I think the optocoupler is damaged. we need to replace it here is it is using P421 octocopular let's check this outlookupler it is p421 TLP 421 it is similar to PC 817 I will use ohm meter with 20 kilo ohm range and here pin number four positive red lead. pin number three black lead this multimeter and resistance mode and this in diode mode here it is one volt that means the diode side is good. The transistor side it is not giving a resistance now I will check this one yes this one is giving resistance and if I check this one it is not giving resistance. now I am connecting pc817 in place of tlp421 now let's power up yes this time the current is regular and if we check input side now it is good condition we have 1.09 volts and output sid now it is 2.84 that means it is now in conduction state and if you check output voltage it is now exactly 24.87 volt and it is regulated before this when this optocoupler was not working it was not switching to the IC at that time 45 volts were here, so these were the problems here this IC, VCC capacitor one resistor and this protection circuit I will arrange these components and I will install it now this output is available if you enjoyed this video, hit the like button if you have any question write in the comments, thanks for watching
