SMPS Repair
Recently one of my friend who work in the maintenance field sent me a switch mode power supply board for repair. This SMPS board comes with a control board for controlling display. The complain was no power and the fuse blown into a very dark color. There must be some components that had developed a direct short circuit that could have cause the fuse to turn into black and by replacing the fuse only will not solve the problem. My next step was actually to use a series light bulb trick but have decided to just scan from above to see if there is any visual indication of components blown. Scanning from above i could see the varistor have some problem. After taken out the part and check with ohmmeter and found that it was totally shorted.
As usual one have to check for any corresponding parts first before you put back a new component and power On it. I have tested the bridge rectifier, power fet and check the big filter capacitor and components in the EMI filter circuit and found all of the components to be good. Conclusion, this switch mode power supply problem was caused by only a shorted varistor and a blown fuse. The indicators (LED’s) in the controller board lit proof that the power supply was working fine upon power On.
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kamal
October 18, 2008 at 7:54 pm
Respected sir,
i want to learn smps repair please tell me about it.
admin
October 18, 2008 at 10:50 pm
Hi Kamal,
If you are from malaysia you may contact me at 603-62778522 for more information or visit the website http://www.noahtec.com/workshop.htm
Best regards,
Jestine Yong
Amal
March 27, 2009 at 6:40 pm
Sir,
I am an engineering student from India. I'm writing this for getting your advice to solve a problem that I'm having with my SMPS.
My SMPS is a 400W one, manufactured by Frontech. The first symptom was that the circuit breaker of the main power supply of my home started tripping when I try to turn on my computer. I figured out that the problem is with the SMPS. So I removed it from my computer and opened it. I checked the components and saw that the electrolyte of the 330uF capacitors on the high voltage side had leaked on to the board, and had spread to other components. So I removed those capacitors and their discharging resistor, cleaned the electrolyte from the board, and replaced those components with new ones. Now for testing, I took out leads from the floppy-drive power connector, connected the red and black leads to a breadboard, and connected a 10k resistor across it, and connected the multimeter leads to measure the output voltage. Then I powered the device. This time, the circuit-breaker didnt trip, but the fuse of the SMPS blew up at the instant I switched on the power. I don't have any idea what the problem is.. Could you please suggest what the problem is, and how to solve it? I think the key to solution is the change in symptom from tripping to fuse-blowing.. But I cant get beyond that..
Hoping a reply soon,
Thank You.
admin
March 27, 2009 at 11:14 pm
Hi Amal,
If the fuse blown then this could be possibly something severe had shorted. It could be bridge rectifier, varistor, power IC/FET and etc. I suggest that you check all components in the primary side.
Jestine
Altaf
May 4, 2009 at 4:43 pm
Respected jestun u r realy a great, great, and great electronics engineer and ur knowlegde has realy impressed me from ur web site i m learnig more and more. the special thing that u r teaching with photos. this is ur different quality from others. but i want to learn from ur self about power supply repairing.
thank u
ur student
Altaf Hussain
admin
May 5, 2009 at 7:55 pm
HI Altaf,
Thanks and if you have other questions please do email me.
Jestine
sam
May 29, 2009 at 3:10 pm
i intrints for smps repair
Altaf Hussain
May 29, 2009 at 5:21 pm
dear respected sir jestin
i have a monitor LGstudioworks 454v. its power switch was underfoult. first i desold the switch then i clean it and solderd in the board. now swithch is working properly but picture is changing its shape from both sides when i increase brightness and when i decrease brightness it comes on normal position. so please help me what i should do for this
thanku
your student
ALtaf hussain
admin
May 29, 2009 at 8:10 pm
HI Sam,
May i know what is your question?
Jestine
admin
May 29, 2009 at 8:12 pm
HI Altaf,
Try check the filter cap at the secondary side of SMPS and make sure all the voltages are good.
Jestine
Altaf Hussain
June 9, 2009 at 2:04 pm
Dear respected '
i have only rapitest Electrical multimeter. and i have no any knowledge that how can i cheak electrolytic capacitor through this multimeter. and i want to cheak capacitor after desoldering from board. so please kindly tell me that how can i cheak electrolytic capacitor by only with multimeter
thank u
Altaf Hussain
admin
June 11, 2009 at 11:11 am
Hi Altaf,
The best is to use ESR meter or digital capacitance meter to test on capacitor. Analog meter is not accurate.
Jestine
Altaf Hussain
June 12, 2009 at 2:03 pm
Respected Jestine
i have 14" colour monitor of philips whenever i on it its working is well but after 20 or 30 minuts it fliks and some times shutdown. please tell me what problem with this monitor
thank u
ur student
Altaf Hussain
admin
June 12, 2009 at 11:57 pm
HI Altaf,
It could be a defective flyback internal capacitor.
jestine
rajashekaran
June 13, 2009 at 6:16 pm
sir,
i just want to know which of smps goes to where, their color coding, wat does a particular color represent, which color is for the supply, which is for signals, etc.. it would be great of you if u can give me these informations.
hoping that u would help...
admin
June 14, 2009 at 9:52 pm
HI Raja,
Try check this link:
http://pinouts.ru/Power/atxpower_pinout.shtml
Jestine
malyadri
July 26, 2009 at 2:07 am
i have one lecray oscilloscope but it is not working means display not coming.
then i opend cover of oscilloscope ,then i measured with multimeter dc voltage no voltage is coming. then i found dc is not rotating.after that i checked fan externally its working good. then i found ac fuse damaged. after ikept new fuse again fuse damaged. after i found varistor gone damaged. waht could be reason please advice me .
admin
July 27, 2009 at 9:22 pm
HI Malyadri,
Since the fuse blown this suggest that there might be semiconductor shorted like bridge rectifier, varistor, power fet/transistor, didoe and etc. I suggest that you test out all components in the power side and also secondary smps side components before you put in a new fuse.
Jestine
biju
August 21, 2009 at 3:47 pm
Respected sir,
my lcd monitor shows one complaint ,that in power on condition about a 5 second display- check display cable- then the monitor in black.
in the last week it felt down to the floor. sir ple give me the what part is complaint.
admin
August 21, 2009 at 8:43 pm
HI Biju,
Since it already drop down the floor i guess you need to check the backlight. A bad backlight could cause display to shutdown.
Jestine
krishanu ray
September 8, 2009 at 2:15 am
I have a smps make by switching system international. we need this power supply circuit diagram from where we get this.
admin
September 8, 2009 at 10:14 am
Hi Kris,
Sorry i do not have the diagram.
Jestine
tshering tobgay
September 10, 2009 at 6:35 pm
i am tshering tobgay from bhutan, so i have same problems SMPS main fuse burn out, then i started to check another component i found that power ic fet was burn out, so i really wants to know how to check other component,
admin
September 10, 2009 at 9:48 pm
HI Tobgay,
I guess you need to get my ebook Testing Electronic Components to learn how to check faulty components.
Jestine
jack
September 17, 2009 at 9:42 pm
Dear Sir: How I can get information about the manufacturer code and specifications of SMPS transmformer. I have a code like TO-4329, TO-9261 and TO-1068, and want to get this information to obtain a knowledge about the operation of the WES-5G power supply manufactured by Tamura Corporation.
Thanks,
Jack
admin
September 18, 2009 at 11:22 pm
HI Jack,
This is the problem as many manufacturers never reveal their code to public thus it would be hard to find out the meaning of the transformer spec. I guess you have to try to email the manufacturer to get the spec.
Jestine
P.THIRUKUMAR
October 30, 2009 at 11:34 pm
Respected sir,
I am in TRC(Testing & Repairing Center) in popular MNC Company....
I want to very clear about the smps repair...It is very needful for my future....
please tell me about it.
admin
October 31, 2009 at 4:27 pm
Hi Thiru,
Try this link:
http://www.repairfaq.org/sam/smpsfaq.htm
jestine
kamlesh joshi
November 23, 2009 at 3:26 pm
what the reapie the smps. I have not for knowledge in smps.SMPS main problem
powesupply .please requir pdf.
kamlesh joshi
admin
November 24, 2009 at 7:36 pm
HI Kamlesh,
Sorry i do not have pdf in smps repair.
Jestine
ashok
December 12, 2009 at 9:37 pm
i use a smps 250 to converter +5v so
i am completed smps tested but not working
so tell me how fing error
admin
December 13, 2009 at 4:02 pm
Hi Ashok,
May i know what have you check? Zero output voltage?
Jestine
dhananjya
December 22, 2009 at 8:20 am
i want to check the smps to know that weather is it working or not. how should u suggest me..
dhananjya
December 22, 2009 at 8:21 am
how to check the smps
admin
December 22, 2009 at 11:16 am
HI Dhananjya,
Try this link:
http://www.repairfaq.org/sam/smpsfaq.htm
If there is no output voltages then suspect the SMPS problem. If there are voltages then suspect circuit ahead of the SMPS.
Jestine
saif
January 15, 2010 at 5:54 pm
sir please tell about my njf9905 chasis primery secttion of smps faulty in which tda4862 is faulty & blown everytime what fault??????????????? pls help
admin
January 15, 2010 at 10:25 pm
HI Saif,
You may need to check all the semicounductors and also switch mode power transformer primary winding.
Jestine
admin
February 5, 2010 at 4:09 am
HI Shahul,
It cam be bad e-caps in the power supply and you need to test it with ESR meter http://www.electronicrepairguide.com/blue-esr-meter.html
Jestine
shahul
February 5, 2010 at 6:23 am
dear sir,
when i switch on my smps its on after immediately it off how to rectify it
satyamohapatro
February 17, 2010 at 3:22 am
Dear sir,
I have a problem in my SMPS i.e my smps start after brushing inside it then again it stop .
admin
February 17, 2010 at 12:18 pm
Hi Sat,
You need to check all the e-caps with esr meter.
Jestine
arvind
February 18, 2010 at 6:45 am
this smps notes for my mail plz
Ranjit Kumar
February 23, 2010 at 6:43 am
Hello Sir I have Zebronics 450w SMPS, which doesn't work becuse there is no PG Voltage.The PG directly comes from IC 2005z but I cant find in our local Market, So Plz give equivalent of pwm ic '2005z'.
admin
February 23, 2010 at 9:35 am
HI Ranjit,
Sorry i could not find the equivalent number for it.
Jestine
shivu
March 5, 2010 at 4:21 am
hi,
i have to learn smps repair, plz help me.....
i have 400w zeb smps. thats switching on but its not comming any display.
i checked outputs its comming currectly even in p4 out also, and also i checked some components with multimeter, droping voltages in components. plz help i con't trouble shoot that.
plz plz help me sir......
admin
March 5, 2010 at 9:01 am
HI Shivu,
Have you confirm it by using other working power supply. The power supply has to be connected to load (motherboard). Check also for bad filter cap at the secondary output side.
Jestine
shanker
March 13, 2010 at 6:04 am
hi how are u
admin
March 13, 2010 at 9:17 am
HI Shanker,
I'm fine thank you.
Jestine
PREM CHAND SUTHAR
April 9, 2010 at 11:15 am
SMPS IS NOT WARKING. SMPS IS DED.
admin
April 11, 2010 at 10:36 am
Hi Prem,
You may need to check all components in the primary side.
Jestine