ATX SMPS Test
ATX SMPS Test is very easy. Just use a scrap motherboard and connect the power supply onto it and place a wire across the two pins shown in the picture below in order to turn the ATX power supply “On”. If possible place two more harddisk to act as load just incase the single motherboard load not enough to switch it on. The symptom could be the fan rotate for a while and then totally stop!
Be cautious that not all ATX power supply support all kinds of motherboard. Some power supply just need back its own motherboard or system in order to function properly. Hope after reading this tips you should not have any more problem for ATX SMPS Test.
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This is the journey of Jestine Yong in Electronic Repairing. In this blog, you’ll find his Electronic Repairing experiences, tips, tricks, guide & recommendations. Feel free to browse around the blog and absorb as much electronic repair tips as you could. Thanks for visiting!
-5v drop in ATX SMPS . How can repair it
Hi Rajeev,
Try tracing the -5 volt line perhaps it could have a filter cap along the input that have high ESR value and need replacement.
Jestine
i have a SMPS with 12 pins 6*2 how can i test that
Hi Shiju,
What sort of SMPS is that? The SMPS connected to what type of board? I need more info in order to help you out.
Jestine
Good day sir Jestine just want to ask. I have atx psu got repaired by myself. The power is all ok but when i check the voltage out put it turns out that the output is like breathing or fluctuating. the 12v is like 11v to 12v, 5v 4v, 3.3 3v… ..Would you give e some tips if it is on the primary or secondary section…By the way i change all the filter capacitors in the primary and secondary section thanks in advance and more power…
Hi Ruben,
Did you plug in a load like a motherboard? Power cycling cause can be in the primary and secondary but the percentage is higher in the secondary side. If this power supply do use an optoisolator, make sure you check this circuit components. I do came across a bad inductor (the round coil) also can cause the power to cycle. Hope this helps!
Best regards,
Jestine Yong
Thanks for the quick reply sir Jestine. Yes sir i plug a load into it. I’ll double check the secondary section thanks again sir for the time and i’ll update you if it works.. I got 3 pcs. of this kind of generic atx and its all have the same problem. It came to my shop with a bad auxilary fan. and no power. I just change all the filter capacitor that bloated in the secondary section and change the auxilary fan. And got a power But
the output is not stable and i hear a ticking sound when the voltage drop to 11v to 12v (like a whining sound tic tic tic tic tic). The ticking sounds like a shorted diode but i change all the diode also thanks again sir… And have a nice day….
My computer used 250w Atx power supply but out voltages 12v,5v,3.3v,nothing is coming,how to rectifing problem.pls tell me.
Hi Srinivas,
Have you check the fuse, switching transistor, secondary output diode, filetr cap and etc ?
Jestine
I want to know how is working atx smps, PLEASE GIVE ME ONE CIRCUIT AND THEORY
Try visit this website:
http://www.kellerstudio.de/repairfaq/sam/smpsfaq.htm
Jestine
My computer used 250w Atx power supply but out voltages 12v,5v,3.3v,is coming,but any load used to nothing is coming,load used to just tripping and no voltage coming,how to rectifing problem.pls tell me.
Hi Srinivas,
Try check the filter capacitor as any bad filter capacitors in the output section could cause power supply to breakdown when under load.
Jestine
how to troubleshoot of complete smps
Hi Bawa,
Check this link out:
http://repairfaq.cis.upenn.edu/sam/smpsfaq.htm
Jestine
very good
thanks for smps test tips
Thanks
i useful this information but i want to know i this above picture which pin u used for sofring that motherboard. can u plse guide me. which pin i used for sorting motherboard.
and in case of if i am using only axe motherboard then which wire need to short.
Hi Sujit,
Short the two wires as seen from the photo.
Jestine
hello sir
my first step if i don’t have any scrap motherboard then i remove all connection of smps from mother board. then i need to put that pin but which two pin req? can u please explain me. i know above picture i need to put that pin in to green and black sockt but which pin require? u got my point example safty pin, or which pin can i get this pin in computer store,and my third step i start switch my i correct if not then please give me correct reply.
my secound question
how much volate get to cpu, ram, lanport, hard disk through power supply.
My third question,
how i know how to identityfy power and rester button if not clearly mention in motherboard, where we connect cabinet wire rester and power supply.
please help me Sir.
sujit
sujitmayekar@rediffmail.com.
please reply.
Hi Jestine,
Thanks for posting this. Just one doubt.
First of all i dont have a electronics background.. I shorted those two pins. Connected a 4 pin plug from SMPS to a fan(I have an extra detachable fan).
Now by giving power supply to SMPS, should the fan work if my SMPS is good?
Thanks,
vijay.
how to repair s.m.p.s
Hi Vijay,
It depends as some power supply need fully load to work properly otherwise the internal fan may turn for a while and then stop. Try put more load like hard disk, motherboard and etc.
Jestine
HI Khader,
Please visit this link;
http://www.repairfaq.org/sam/smpsfaq.htm
Jestine
HI Sujit,
Try this link:
http://www.smpspowersupply.com/connectors-pinouts.html
Jestine
Hi Jestin,
The power button of my PC is not turning on the PC. After testing I found that the Motherboard is not turning the SMPS on. It works fine if I short the PWR_ON with ground with a wire and then press the Power on button. Can you please suggest what could be the problem?
Thanks and regards,
Kinku
Hi Kinku,
From your description it seems that the problem is in the motherboard but sorry i have never come across such problem in motherboard thus i could not give any expertise advice on this matter.
Jestine
what is the full form of smps.
Hi Aspak,
SMPS means Switch Mode Power Supplies.
Jestine
Sir, I am searching for an equipment which can test or measure the parameters like VOLTAGE and CURRENT coming out from the SMPS of COMPUTER. I am final year student of ELECTRONIOCS AND COMMUNICATION ENGINEERING and going to deplope an equipment which can measure all test points of SMPS.
Hi Akash,
That’s good and keep up the good work!
Jestine
I did this on a old PSU and it did not care about the scrap motherboard and the hard drive. I just used a cable from the green to the black and I did it. My PSU is not that. It supports 220V but it also supports 110V in my area.
HI Neel,
May i know what is your question?
Jestine
Thank You sir…but please provide me some information regarding SMPS TESTING and CALIBRATING EQUIPMENT in details…..please mail me as early as possible…
it right sir
what can i do when ps volt 2.5
Hi Akash,
Sorry i do not have the calibration of equipment info. For the SMPS testing i guess you can read from this blog post to test the SMPS.
Jestine
HI Ramesh,
Could you elaborate and provide more info?
Jestine
My atx smps is creating some problems sometimes it is working fine but in most of the cases the power from smps suddenly gets off when pc is running and when i removed all the connectors and main cord of smps it started working and than after some time the same fault it gave what can be the problem and how can i resiolve it.
HI Neeraj,
Try check the filter capacitor first at the output of the smps.
Jestine
how should i test a smps mother board and what test should be done on it to know its performance
Hi Suresh,
Connect the smps to a load and power on. Test all the output voltages with your meter.
Jestine
Thank you very much for your tip about testing of ATX SMPS. Can you please tell how critical is +12V supply if measured as 11.75V (partial load) and full load 11.48V with a digital VM, for running on-board VGA graphics on INTEL DG965 MB. The SMPS runs all fans, HDDs etc. but no video output. Monitor and cable fine. SMPS and system have been running fine for almost 3 years. It is 20+4, 400 W.
Thank you.
HI Atul,
Have you replace with another good SMPS to make sure is the power supply fault. As for the 12 volt, most motherboard need at least 12 volt to run. I guess you have to confirm first whether is the SMPS or the motherboard fault.
Jestine
i want study repair about latop.thanks
my PSU into mainboard do not run
HI Thant,
Sorry no laptop repair course.
Jestine
Hi Thant,
I guess you need to open up the power supply and begin to check on the components like fuse, bridge rectifier, power semiconductors and etc.
Jestine
Hello Sir am H/W engg i want to learn smps circuits so pls send me details thanking you
HI Skani,
Try this link;
http://www.repairfaq.org/sam/smpsfaq.htm
Jestine
Hi Jestine,
I’ve got a Intel D945GCL working fine. I have a Toshiba external HDD 250GB which was working fine until some time ago. My system doesn’t read it at all now. It works on all other systems and laptops. I figure out from my knowledge that the problem is power shortage as i have 3 internal HDD’s, a DVD Writer and a fan connected to the SMPS.
Could that be the cause of the prob?
And also, the 20-wire cable from the SMPS(as shown in picure above) is connected to a 24-pin socket on the motherboard. A separate 4-wire cable is left disconnected which would fit in the remaining 4 pins. Why is this disconnected? Does it provide additional power to the motherboard??
Please help. Thanks.
Hi Abdul,
Yes it could be power shortage. You can always use a higher watt power supply to test it out. The 4 Pin Molex P4 12V Power Connector is use specifically for Pentium 4 Processor Motherboards while the 6 Pin AUX power connector was added to provide extra wattage to motherboards for 3.3 and 5 volts. Does the power supply have the 6 pin AUX power connector? This connector is rarely used anymore. It’s most commonly found on older dual CPU AMD motherboards.
Hi Jestine,
My SMPS does not have any 6 pin connector. It has one 10×2(20-pin)(connected), two 2×2(only one connected as i mentioned earlier), four 4×1(all connected to HDDs and DVD Writer) and one floppy connector(disconnected). Also, i use the Pentium Dual Core 2.6Ghz Processor. So, do you think i should connect the 4-pin connector in the left out 4 pins? Will it help me in any way?
Thanx a lot for clarifying my doubt which has had me puzzled for long.
Thanx!
Hi Abdul,
I’m not sure about that. May be try to disable two of the internal HDD and see how it goes first. By the way when you said your system does not read at all, does it mean it just “hang”? or could you elaborate more?
Jestine
hi , can i get some help, my pc starts but no display, all fans working, i checked voltage on all pins of my 20 pin smps, it was almost same as expected (checked from this - http://www.subedartech.net/docs/pc/connector_atx_pinout.GIF ) but little voltage on pin 8 (power_ok)almost .5v (no voltage mentioned in above picture) what should be the voltage if ever i need to know it, but most important is what the problem is and how i can rectify this, please help
Hi Parvaiz,
If the power_ok is only .5 volt then the power supply have problem. A low power_ok voltage could cause no display. Check all e-caps in the power supply. Sometimes a bad main filter cap could cause no power good 5 volt.
Jestine
thanks a lot for such an incredibly quick response jestine, i will soon check it out, but this comment is just to thank a wonderful person like you to respond so quickly, thank you again
No problem Parvaiz!
Jestine
Hi Jestine,
I did as you asked me to. Disconnected 2 HDDs and it all works fine! The external HDD got detected and working. Was definitely a problem of power shortage.
And when i had mentioned that the system does not read the extHDD actually meant that no “new hardware found” notification was displayed and the disk within the extHDD was not rotating freely as i could feel from without by the vibration. It was taking short jerks but was not working normally.
Also, do i have a solution that lets me use all 4 HDDs at once with enough power and no problems??
HI Abdul,
I guess the best is to use a bigger watt power supply as all power supply should have some extra wattage left after connected to all the loads. Otherwise the transformer may run very hot and eventually blow up the power supply.
Jestine
Hi Jestine
my atx smps was not working for last few days, yesterday when i connected mains to it, there was a little explosion, i opened the smps and found main filter capacitors somewhat out of shape with bulging/broken top, and changed both and also the blown fuse, when i connected mains again there was a hard sparking near power transistor D13007 and it was blown (broken into two)also the mains fuse blown (there are 2 more transistors in the same row, first is same D13007 other is 02N60P), what is the possible cause of this problem
moreover just forgot to mention that somebody previously had changed the switch position from 220 to 110 (possible cause of blown smps) , voltage standard here is 220, now please help me to sort out the problem
Hi Parvaiz,
Open up the power supply and check the fuse and the big filter cap.
Jestine
Hi Parvaiz,
Since you found so many components burnt, i guess you have to test out all components before turn the power supply on again.
Jestine
thanks jestine, i will try to test all components and possibly it will take lot of time, i have another atx smps, it just dosn’t boot, i mean after i short fps_on and earth(common) nothing happens , no fan running etc, can u help what i should check?
Hi Parvaiz,
If there is zero volt output from the power supply then i guess you may have to start to check the fuse first and the primary side components. It could be an open resistor, shorted transistors and etc.
Jestine
i have one computer atx smps is working bu no PG (power good ) how can fix this SMPS please help
HI Fazil,
No power good problem can be cause by bad filter cap in the primary or secondary side. Sometimes it can be an open resistor nearby the PWM chip in the secondary side.
Jestine
please reply me
May i know what is you question?
jestine
hello sir ,
my atx 400w smps is not working properly ,how can i solve it
Hi Saurav,
Guess you need to open up the power supply and begin to test on the components especially the primary part like fuse, bridge rectifier and e-caps.
Jestine
Dear all,
I am computer service engineer. But i have no knowledge in smps servicing. My SMPS is not working. That is fan is not working. Please give me solution.
Very Good Future and very nice thanking you
because i am facing that the problem in hardware thanks for said to all
Hi,
We want to form a Computers SMPS Manufacturing Plant near Mumbai, INDIA. We welcome any suggestion and knowlledge sharing in this regards.
Prakash
HI Prakash,
Congrat on your plan.
Jestine
Hi M.S,
Check the fuse and the primary side components. Check also the secondary filter cap too.
Jestine
Help full one
after connecting green and black do we really need another load like mother board.
HI Raja,
Some SMPS need extra load i.e motherboard.
Jestine
thank you
hi jestine,
my smps does not work, actually when i push power on button on my pc , fan rotates but stops automatically after 1-2 seconds, moreover if i take out 4 wire connector from smps out of mother board and keep only 20 wire connector intact, smps seems to work fine albeit pc does not boot, i have tried this smps on almost 3 or 4 motherboards, any help?
Hi Parvaiz,
Have you check the e-caps in the power supply?
Jestine
tganks
smps when switch on it make a sound,what the problem
there is no problem in output.sound is always before i switch on smps
Hi prashobh,
Do you mean the power supply is working fine except that you heard the sound? Is it a high pitch sound?
Jestine
i have a faulty smps power supply atx p4 400w i am not getting voltages on the secondary side of the smps ‘xmer it seemds it is not triggering earlier one 1000mfd/16v electrolyte capacitor was busted and the round coil got bornt.I replaced the capacitor but there is noaction the round coil is ok i have checked.Pl give solution.
Regards
HI Rajendra,
If the round coil burnt then it is very difficult to get back the same part. If the coil is good then i guess you may need to test all the components in the primary side. Check also for shorted components in the secondary side.
Jestine
pls help me,
I found that one 1/2 watt resistor and some other resistors & one power transistor is blowned ,when i replaced all and no problem with fuse my SMPS fail to give output even shorting pwr on with gnd. I chked working condition only by chking fan working, is it require any other load to be connected. How to findout any other problem with other components?.
Hi Nidhin,
You need a motherboard and if possible check the secondary side diode output too. You must scan all components in the primary side.
Jestine
Hi,
My Sony computer has ATX power Supply and I get 5.34V for 5V. How do I fix this.
Thanks,
Srini
Hi Shini,
Try check the filter cap or even directly change the coil.
Jestine
i want solution about smps
HI Knaresh,
Please visit http://www.PowerSupplyRepairGuide.com
Jestine
dear sir,
My smps is working,but it gives 3v for 5v ,5v for 12v,and the output current is too low.cooling fan was working correctly and now it is dead.but the output is same as voltage mentioned above.pls help me to troubleshoot this problem.It dosent have any atx -20pin connector ,but it have molex and mini-molex connector.wat do with “power good” wire?
HI Nidhin,
I suggest that you check all the e-caps in the power supply. Check the cap in the primary and the secondary side. Power OK (power good) is a status signal generated by the power supply to notify the computer that the DC operating voltages are within the ranges required for proper computer operation (+5 VDC when power is OK)
Jestine
my SMPS when put on for long time it gets dissconnceted automatically n when i again try to switch it on there r sparks coming out of it do i have to buy a new one or this smps could be repaired
HI Kunal,
It could be dry joints in the primary power side area. If you have never repair any power supply before and do not know about the safety, i suggest that you buy a new unit.
Jestine
i have purchase a digital multimeter and checked well condition SMPS but output power not show properly. for exsample:+12 shows +11.45.
Hi Sujit,
Have you check the filter cap? Is all the output low or just that line? If all output are low, the toroidal inductor can cause such problem.
Jestine
my smps problem with sb volt 5v in but other power supply not volt
pls. solution this problem
HI Anil,
Have you check all the filter cap? Did you connect the power supply to a load?
Jestine
i want to see the schematic diagram of your product which is the ATX power supply tester, is it possible? can i see all the schematic including the internal schematic and external? can you please give them all for our project proposal?
HI Reymark,
Sorry i do not have ATX power supply tester schematic.
Jestine
I M learn chiplevel
Hi Nafish,
Could you elaborate?
Jestine
Hi i m nafish ahmad
Nice to know you Nafish.
Jestine
yesterday when i connected mains to it, there was a little explosion and nothing displays on my pc.please anybody help…..
Hi Bhimsen,
You need to check on the bridge rectifier and other semiconductor components in the power supply primary area since you said the fuse blown.
Jestine
i want to lern more about atx smps send me feedback
HI SANKAR,
All i have compiled it into an ebook http://www.powersupplyrepairguide.com
Jestine
but some times it worked but there occured no display
HI Mushtaq,
You may need to check all the filter caps.
Jestine
I am faceing ATX SMP 110V Its restarts again & again than stop
Please which portion may be problem (Components) should i check
HI Mahesh,
It can be filter cap or any bad components in the primary or secondary section. Make sure the power supply is connected to a load like motherboard and the filter caps are good.
Jestine
Dear Sir.
I would like to ask you about signal to or from SMPS PSU.
1. PWR FAIL
2. PWR GOOD
Is those out or input to the PSU?, whats the level?.
Thanks
HI Ronald,
Power good is 5 volt and there is no power fail signal. The power good is an output signal from the SMPS.
Jestine
sir my snps problums is not work properly out put power is dead
sir plz help me
HI Sur,
You may need to check all the components in the power supply side.
Jestine
When I am trying to power on my PC. It start for 1 seconds and stop. I have changed my smps . Now its working fine. What may be the cause . Is it possible to repair my SMPS.
HI Rana,
Yes it is possible to repair it but you may need some skill on testing those electronic components particularly the ESR of electrolytic capacitors.
Jestine
My PC keeps switching off after few minutes of working. Sometimes it works for hours before switch off. some times it switches off in minutes. I checked the temperature of the CPU it is around 40-50 C. I am using windows and ubuntu ad dual boot. in both the OS the problem s there. My friend says thet this is SMPS problem. He opened the SMPS and says that somethng( i think capacitator) is looking bulged.He asked me to replace the SMPS. Cant’t it be repaired. I am using Zebronics 400W(SATA)Economy Series( 20 +4 pin). My question is if there is some problem in the SMPS it should not start at all. How come it works for hours sometimes? pls help.
HI Faizal,
Your friend is right and you need to replace those bulged caps. Bulged caps in the supply line can cause voltage to be low thus affecting the pc motherboard performance.
Jestine
my computar starts after 10 minits. is smps is faulty? what is the service center cantact at mumbai or kalyan
HI Satish,
I’m from from mumbai thus i do not have info on that. Your problem could be the motherboard or the smps. You may need another good smps to confirm it. If the smps is the cause then check inside to see if there is any bad caps or not.
Jestine
I replaced the SMPS. Still having the same problem. The PC shuts down after 1-2 hrsof use. i checked the CPU temp using a program called speedfan. the temp is around 30-40 C. What else could be wrong.
HI Faizal,
I’m not sure about the temperature but since you have replaced the smps then it is not the smps fault. Did you see any bulged e-caps the in the motherboard?
Jestine
yesterday the PC was working fine. i am not able to understand this. the warranty is going to end next month. As I purchased an assembled PC I have to take the specific component which is having the problem. And the problem is also random.how to pinpoint that a specific component is faulty.
HI Faizal,
Since you said the smps is good then send the motherboard for warranty claim.
Jestine
I am recivin 10. V in red,25v in yellow so tell me what is problam
Hi Ramsingh,
It seems that the power supply have overvoltage problem. If this power supply have the optoisolator circuit then please check this area (secondary side ) for high ohm resistor and etc. Check all filter caps too with ESR meter.
Jestine
thanks its working…………
I have15 inch lcd moniter. it displays goes off within 15-20 seconds but the power LED remains ‘ON’ also secreen shows half white tell me what is the fault
HI Jadhav,
Make sure there is no bulged e-caps and the backlight is good. One of the backlight have problem could cause it to shutdown. Assuming you have solve the problem and the display half screen only then the problem is in the lcd panel and there is no way to repair it.
Jestine
when i short green and black color wire then my smps fan is running but when i conncected it to motherboard then cpu fan running for short time and stop what is the problem plz solve
Hi Raju,
It can be the POWER SUPPLY itself or the motherboard have problem.Try use another working power supply to test and see how it goes. If power supply fault then check the filter cap for bad ESR.
Jestine
Hi
I have Dell Work station (Precision 650) its not swithing on. How i will be chek SMPS is good or Bad ?
Hi Neyaz,
You need to open up the power supply casing and check for the fuse and other components. However, if you do not have experience in electronic repair i suggest you send it to a repairer.
Jestine
Respected Sir,
My PC SMPS fan is not working, so what I do now sir. Please give me any tipes about this regards.
Thank You Sir.
Hi Bhakta,
Only the fan not working? Is the power supply working? If only the fan then i suggest that you service the fan with oil based spray or replace with a new fan since it is quite cheap nowadays.
Jestine
Hi
I already open SMPS i know litilbit about electronics. Fuse is good and all components is loking good. but in odanary SMPS option is their short the Gren and Blue Wire then its run if its good condition but in my case this is fully difrent SMPS (NPS-460BBB). In ckt one pin is mention PS_ON. i was short with ground but nuthing is happen.If you know Exect pin for swithing on please tell me.
Hi Neyaz,
Usually for ATX you need to short the two wires. In your case, it could be different wires but you already mentioned that you have shorted the PS_0n to ground and still no power then the power supply itself have problem. If you still no confident about those pins you can connect the power supply back to the system and turn it on from the system.
Assuming if still no power then you may need to check the components in such like check for shorted secondary diodes, or even bad start up resistor. If the power supply totally have no output (zero volts) then i suggest that you test all components in the primary side.
Jestine
Hi all,
when I power on my computer the SMPS fan not move & in motherboad fan hdd lights not glow.I shorted green +black pin of 20 pin smps connector the SMPS fan moving now but no movement in motherboard no fan move,no beep.I fixed the 20 pin connector(SMPS)on m board & On moterboard PWR pin shorted but still not working SMPS FAN AS WELL AS M BOARD PLEASE HELP ME………..
Hi Prakash,
That means you may have a blown power supply because it does not have response at all.You need to open up the power supply and check the components especially the primary side. It can be a blown fuse, shorted semiconductor or even an open resistor. If you do not have experience in electronic repair i suggest that you send it to a professional.
Jestine
i got a complaint on switching transtitor .transistor is ok ,no switching done what to do next.
Hi Jimmy,
You may need to check all the components in the primary side. Sometimes a bad secondary diodes or filter cap could cause no power symptom.
Jestine
Dell MK463 (NPS-750 ABA) PSU not switching ON. +5V Standby & PS_ON signals are present. The relay on board doesn’t switch ON & fan doesn’t rotate when PS_ON is grounded. The supply to relay coil is only 6V instead of 12V when PS_ON is grounded. No leaking caps found. Kindly help to troubleshoot further.
HI Mani,
Try check the optoisolator IC area especially the resistors or even the Tl431IC. I’m not sure if this model have this components or not but if there then you may need to check it. Check also for bad components in the primary side especially the current sense resistor because an increase in resistance value could cause the output power to drop to half.
Jestine
hi thanx for information
My SMPS Properlly stop, what reason. Sugesson me With Diagram and Point to Point
HI Mangat,
Sorry i do not carry any diagram. I suggest that you check all the components in the primary side. Check also for shorted diodes in the secondary side.
Jestine
Sir,
i want to know that floppy drive connector has one red wire to supply 5v and another yellow wire to supply 12v power supply.now my question is why do we need to supply these two wire of different voltage to the floppy drive.
Hi Vishal,
12 volt is for the motor and 5 volt is for the circuitry.
Jestine
smps diagram
HI Kazi,
Sorry i do not keep any schematic diagram.
Jestine