#247 How to repair Computer Power Supply Troubleshooting Repair Tips

the green wire this five volt are connected to this pin pin five when this pin number five have five volt it will not turn on salaam friends in this special video why i say special because i receive too many comments sir we are facing problem we don't don't find voltage on purple wire we are we have dropped voltage we cannot when we apply power to turn on atx power supply it does not turn on i will discuss every possible fault every possible problem in this power supply if you are working on some power supply if you don't have a good knowledge how to work with electrical circuits never take a risk very high electrical voltage and they are very dangerous so if you are not aware kindly don't do this basically all snps power supplies switch mod power supplies are same just only maybe a very small difference will be there but if we have some concept how to deal with power supplies any power supply if we discuss tv power supply if we discuss led power supply if we discuss washing machine power supply if we discuss any power supply keep the area clear clean no electrical debris like washers screws it should not here it should be away second use a series lamp i am very sorry for being late because i have approximately more than 300 requests for videos sir start tv series or start led lcd series horizontal circuit series parallel because my videos are approximately one hour long or half more than half hour why when i want to discuss something i need time so i am sorry for late but inshallah i hope so i will address all the questions and it's my pleasure but for making video for it's a very lengthy job and i have my own office work i have my own project so when whenever i have some free time i make lessons any power supply it have then we have dc bus from dc bus it is distributed in two parts the first part that is standby its duty is to apply voltage for vcc by c for main power supply main power supply or secondary power supply we take 300 volt dc 300 volt dc here okay it will stand by voltage here this voltage will go to pc and pc computer will give ps on command when ps on command and vcc and these voltage are available it will generate power output and this power will monitor through the supervisor ic and this supervisor ic will give feedback to main power supply in standby section 5 volt sb we have here and it have its own monitoring circuit feedback circuit to monitor it if five volts are okay at that time it will take feedback that it will keep working if five volt are missing nothing will happen we need this voltage to power on this and we need 5 volt sb to reset the computer to apply power to the computer motherboard to act on the power on command when anyone will press the power button we will receive voltage at this power supply section this controller and this will turn on the power supply and we will receive voltage by switching of this voltage 300 dc volt we will take different voltage 12 volt plus minus 5 volt 3.3 volt like that so on as we discussed we have emi filter and safety circuit what is emi filter and safety circuit fuse ntc sometimes we have over voltage protector here this time i don't have over voltage protection okay no problem sometimes we have filter here this time we don't have no problem because every design have different configuration fuse in this power fly fuse is here and ntc is here here fuse is here and tc is here so some time it is changing of the components sometime we are using this ic here 8205 here is 7520 that is also sdc 921 2921 tl494 6105 anyone i see design manufacturer well different number of pins will different but the function will remain same i have this power power supply we have in the in this diagram in this this is very best power supply we have some filter here bridge rectifier here after bridge we have here a 5 volt generator that is small transformer and then five volt section we will receive five volt and that time we have also a bison power supply 16 volt biasing power supply for the transformer signal transformer and in the end we have 7527 7527 supervisor ic it will receive voltage from the output section and it will check them for proper availability if any voltage is missing it will not allow to turn on power supply okay this is the first design if we see some other diagram here we have six one zero five we have three point three volt sense circuit actual sm in atx power supplies the biggest headache that is for repair it is very best supervisor it supervises all the outputs if any output is going wrong up or down it will disable the output it will stop the switching what we will do to work on any atx power supply just only check the part number here on this ic 7520 another ic stc2921 here is another power supply 6105 it is taking outward from output section actually this is the main issue these ics very rarely damaged these are very safe and protected but if we have some problem in output section they will monitor the output and the same time they will not allow the output it is the basic issue for repairing these power supplies just only go to the internet check the data sheet see the pin out where is 3.3 volt where is 5 volt where is 12 volt these three inputs one two three these three pins of any ic in this ic we have at pin number three four five in stc2921 i have pin number one two three actually this three pins are the basic problem then you have to check the vcc if we have vcc then we have to monitor these three pins our problem will be sound and today i am discussing 7520 ic it have one two three if we see here stc2921 one two three one two three pin number four pt pin number four pt five is ground six is rt seven is c1 so 8 is c2 it is output 9 is remote 10 is ss soft start capacitor p power good detector this is protection vcc copy out here is here is voltage adjustment we are just a negative input inverting input not inverting input sorry non-inverting inverting input so in this sdc2921 we have v and negative v and positive it is also the same things so we can say 7520 and sdc2921 are similar if we see this ic two zero zero five then one is negative inverting input here is negative inverting pin number 15 so 15 and 1 op out pin number 16 here is op out 14 so it is change we adjust pin number two we are just pin number 16 so it has some change in pins other one two three the similar same pt is here pt is here ground pin number five here is ground pin number seven ct here is ct here is capacitor soft start capacitor here pin number 10 here is ct pin number eight c1 c2 output of pulse switch modulator to drive remote on command pin number nine remote on command pin number eleven so it's working like this so let's start first problem in any power supply the fuse burn out how to check set multimeter to continuity connect at input terminals if you find shark that means we have problem in somewhere any component is short diode is short ntc is short sorry ntc no and it says okay it does not shout maybe we have voltage arrester short then a very simple and basic test another warning if you are not aware how to deal with these components or you don't have a good knowledge never try this because here are very dangerous voltage so now we have two capacitors here one and two and they are connected one they are connected in series one capacitor here these are the test points one capacitor here this this end is negative this is positive end of the second capacitor and this is negative end of the second capacitor so positive negative positive negative so this end is negative and this end is positive we will find dc voltage here set multimeter to diodes connect one lead capacitor negative terminal one lead here one lead here it will give point five volt drop of the resistor of the solid diode of these diodes if you find continuity here like short circuit how if your fuse burn out again and again i can say this diode is short circuit i made a jumper for this diode this diode is short circuit here i find okay now go to the other terminal we will find if one diode is short we will find continuity here if the other diode is short we will find continuity here any one diode will short it should not give continuity here if any terminal gives giving continue to direct that means the bridge rectifier is bad at this point this point we received continuity now swap the leads red lead black lead now it should not give continuity because red lead was here red lead was here and i received 0.5 0.5 voltage drop across the two diodes now i will change red lead here here so it should open now move this lead first we tested this end now move to second capacitor this capacitor positive terminal this capacitor negative terminal this capacitor positive terminal move here power must be removed power should not applied if you test with applied power you will damage the multimeter or the board or it will make problem so we tested the input section now continuity to both end of the capacitors if you find short circuit here that time we will we must have some problem something short circuit here how is the circuit working we applied voltage here point it is coming directly to the diodes this diode and this diode the second end from here to fuse here is fuse from fuse ntc and these diodes this end is applying positive voltage here and this end is applying negative voltage to the thrusters so let's apply voltage select multimeter to ac and now this is our lamp series lamp is very useful for testing the power supplies we can see the if the power supply is good the lamp will start for a while turn on and then it will go in off state if it is on directly that means we have something short in the power supply you see it will give a slight illumination then it's off i will demonstrate how we can find we will find the problem set multimeter to ac in the input we are finding 200 231 volt anytime you find the lamp is illuminating that means we have something wrong we have to check the circuit now in first step set multimeter to dc connect one lead to capacitor negative terminal and other lead to positive terminal we must find 300 plus volt if any capacitor is bad how we can determine check ac voltage how much voltage are here 231 volt 231 volt multiply it with 1.414 volt it should be the capacitor voltage ac input this is formula 230 multiply with this these voltage must be at the capacitor 330 plus volt if you don't find these voltage that means if you find 220 volt dc that means we have some problem 270 volt dc that means we have one capacitor bed so here i have 325 volt that's good that means our circuit is working in the first step for testing this circuit any atx power supply you have to go directly to this purple wire this purple is standby sb standby we have to go at sb sb is here on this on this capacitor and this capacitor yes this capacitor is standby so we find 5 volt 5.2 volt it must be available if we don't find that means our power supply will not work if this power fly is not available that means because this is the basic key point this ic and we have to check vcc at pin number 13 of this ic i will connect only to ground black lead for easiness black lead here now we will go to pin number 13. that is 1 2 3 4 5 6 7 8 from left to right side 1 2 3 8 9 10 11 12 13 14 15 16. it is pin number 13 5.2 volt this voltage must be available at this pin if you don't find what to do we have to trace the standby section where is standby section we have here any power supply power transformer signal transformer the small one signal transformer the small one and standby power this transformer is standby power so we have to trace this in some power supplies there is a transistor based some they have ic this smps this switch mod power supply have ic forget about what is there it will take direct voltage from the main capacitor as we discussed it will take direct voltage to standby section and it will give us 5 volt so this ic will drive this transformer and we will receive two type of voltage 5 volt yes that's another question from standby section we take two power supplies five volt and 12 volt because in the secondary we have two power supplies two windings one two three center tape transformer one pin is ground and here we have main diode one diode and two diodes these two power supplies the one power supply is used to give 5 volt the second 12 volt power supply will apply to the signal transformer center tape winding the center tape will take 12 volt from standby section so in the standby section we receive two type of power supplies the first power supply we have we can see here we have two capacitors first capacitor first capacitor second capacitor the first capacitor is connected to this diode that is here from this diode output section cathode side 5.2 volt and there is another small diode inside here inside this diode it will connect it to this capacitor it is giving 9 volts from 9 volt from 9 volt to 12 volt we will find here this 9 volt is used to switching of this transformer signal transformer when the power supply will start it will take these voltage for switching because that time we are not finding any voltage for switching so these voltage will be applied to the signal transformer when the power supply will start functioning at that time this 12 volt because here we don't have power supply this point at that time these 12 volt will be switched there is a diode here this at that time this diode will apply power at that time this diode will apply one way power for this transform so we need two type of power supplies from standby section and we have to check this capacitor and this capacitor if we find 5 volt but we don't find this voltage power supply will not start or maybe we find this capacitor bad at that time power supply will will turn on turn off turn on turn off because it will not hold the charge so you have to check this voltage 9 volt at this capacitor 5v it is our basic requirement checkpin number 13 5.1 volt standby section 5.1 volts then we have to see the green wire green wire must have 5 volt around 5 volts if we don't find these voltage very little components this is section 1 transistor here one transistor four diodes three or four diodes in this section in the in the driver section inverter driver section one transistor and it is flyback system one diode two diode three diodes three four resistors these are the total components one optocoupler here and we have two resistors for biasing here for the optocoupler just only it is total combination in the output section we have this rectifier and that rectifier one capacitor here one capacitor here this will drive this will apply the bisect voltage for this chip and from our resistor we will find this voltage at power on command now check pin number nine of this ic here is pin number nine pin number nine should have five five volt sb sorry five volt the green wire this 5 volt are connected to this pin pin 5 when this pin number 5 have 5 volt it will not turn on for this ic it is pin number nine for other ics maybe we will need another pin for standby now i will make ground so i ground it this five volt star power on ps on command and we will check the voltage at this pin it must be zero if we don't find voltage if we don't find ground here we cannot turn on power supply first step now we check power we have 12 volts we have 5 volts ground 3.3 volts 3.2 3 volt if we see pin number one 3.3 volt it must be available why because this ic needs 3.3 volt for working proper working pin number one 3.3 volt pin number one i need three point three v three three pin number one v three three three point three volt must be present so 3.3 5 volt v5 that means 5 volt must be present then we have 4 volt this is 12 volt section 4 volt from 12 volt section if you don't find these voltage here these three are the basic voltage we must find here it should be available if we don't find this voltage because if we have something wrong in 12 volt section this 4 volt will drop at that time we will not find the proper output this ic will allow once turn on and then it will go in off condition why because it will not find the 12 volts if 5 volt here this 5 sorry this 5 volt this 5.19 volt the same voltage are applied here if we don't find these voltage we will face problem so for working proper functioning we have to verify this circuit suppose our this rectifier is not working good 12 volt section 5 volt section is not working good 3.3 is not working good we will immediately it will disable the output it will disable the switching so c1 pin number seven it is in that condition when it is working good c c we can set frequency at hertz 37 kilohertz 37 kilohertz 37 kilohertz when the all voltage are good these two signals are applied to these two transistors here [Music] this transistor and this transistor when the all inputs are good 37 37 so it will apply to base of this transistor and base of this transistor 37 so these voltage will switch through these tracks to this transformer this small signal transformer the center one central one and after that we have a pulse forming network there is a pulse forming network in the secondary side of the signal transformer it will make a pulses perfect shape for switching these two transistors and these two transistors will switch this main transformer and we will find the voltage and secondary if we have some issue in this section we can bypass the safeties to test it for example our this section is short from here or from the outside pin number three locate the pin number three for 12 volt pin number two for the five volt pin number one for three point three volt one two three and number two to this resistor 10 ohm resistor and 10 ohm resistor is connected to this 5 volt so 5 volts are applied to this resistor for testing if we have something wrong maybe our this capacitor is bad this capacitor is bad any capacitor is bad remove this resistor remove this resistor and connect pin number two to standby section now i will collect oscilloscope pin number seven and eight seven eight eight so i connected this ground yellow is ground and i will connect ground line to both inputs of this oscilloscope and when you want to connect oscilloscope it must be isolated oscilloscope must be isolated from main power supply this channel one channel two it is in good working condition this time i am taking pin number seven and eight output it is a good working condition the both signals are switching this time i have output i have 12 volt i have 5 volt i have 3.3 volt for example now so this time our both channels are switching now it is a good working condition if i have for example any power supply is short however this jumper is connected the other voltage main supply is connected this supply go in off condition now i remove power and i will turn on after a while until the capacitors discharge now the level is going down standby section is grounded now it started switching again it is in this condition that we have voltage any power supply is out of limit or it is loaded it will make problem what to do now we have to apply a simulated voltage on this pin suppose i have a permanent short circuit here for example our this capacitor is short there is that for example our this capacitor is short permanently from inside however this diode is short what we can do we cannot find output in that case we have to make a bypass how to bypass i have uploaded a detailed video i will give the link in the description and you can find that in that condition we have to remove 5 volt sense line 5 volt sense line this this resistor we will remove it then we will remove a resistor connected to pin number three pin number one 3.3 volt section so in that condition we will remove yes this resistor this is 3.3 volt we have to remove this resistor and it is connected to 3.3 volt section then we have to disconnect pin number pin number three that is 12 volt sense line this resistor 1k resistor remove this what we will do five volt sb you have to take one two three resistors the first resistor we will make this one 3.3 k this resistor must be 700 ohm this resistor 1k we remove a resistor connected to pin number two remove this resistor and connect this pin number five to vsb 5 volt sb this pin number 2 to the size 7520 if you have another ic if you have 7 8205 at that time you will connect for pin number 4 to sb and remove the resistor and connect five volt to that pin okay v12 it need four volts so remove the resistor connected to pin number four sorry pin number three in this condition and if you are using this ic that time pin number five it will here pin number five so it will go to pin number three here we will find four volts here we will find 3.3 volt this 3.3 volt pin number one remove resistor one open one end open one end i did uploaded a detailed video and i will give the link of this video in my description so you can find this video and it is very easy just only take three resistors remove this resistor this is this resistor and connect this because it is five volt connected to five volt sb when we will do this job what will happen because this ic will receive power when the ice when the power supply is powered on if we have some issue in the any circuit 3.3 volt section 5 volt section 12 volt section if we have any issue any problem in any component diode is short capacitor is short capacitor is not holding the charge it is not regulated so this ic will not allow to turn on the system for testing which section is making problem we have to simulate with this voltage so this ic will consider that everything is good so when you will make a jumper between green and black it will turn on because it's possible i have this voltage so in the in that case your power supply will work properly if it is done if it does not work again when you connect this in this way that means we have problem here r then we have to check the frequency at pin number seven eight of this ic because it is c one and c two collector number one collector number two if we have any issue in regulation this ic will not allow to turn on the system so when we will make a bypass in this way this ic will turn on after that we we can check the voltage here here here if any voltage are out of limit we can check that circuit immediately it is very easy just only make a bypass in this way i hope so this video is good for you if it is good you can like subscribe and share if you want thanks for watching

Channel: Haseeb Electronics

Views: 47,770

Keywords: how to repair computer power supply, computer power supply in hindi, how to repair, atx power, atx power supply, atx power supply to bench, wire color code, turn on computer power supply, turn on computer power supply without motherboard, turn on computer power save mode, switching mode power supply, smps, switching mode regulator, how to repair switching mode power supply, how to repair smps, haseeb electronics, computer, sdc2921, tl494, troubleshooting, repair, tips

Id: X5vEb4RKPF0

Length: 42min 33sec (2553 seconds)

Published: Fri Aug 21 2020