Problem with SMPS

[ashfaqueahmadbari]

A couple of years back, my SMPS was replaced coz my last one stopped working during a power spike. I just opened it and found that only the fuse was blown. Is there anyway I can check whether the SMPS is working after replacing the fuse without connecting it to my PC or to anything else?

 

[aljamri]

a blown fuse is Symptom for another problem. so it is likely to get the replaced fuse blown again and may be with BANG.

 

[dannix]

well you could plug it in without it being plugged into your laptop after changing the fuse, but as above its prob going to blow. I had the smae issue last week, replaced the fuse and bang, at least it was not plugged into the laptop

 

[ashfaqueahmadbari]

I'm pretty sure it doesn't have any other problem coz it happened during a power spike when my UPS wasn't connencted. could you tell me how i can switch it on after connecting it to the mains?

 

[jpanhalt]

Do you know how to turn the PS on without connecting it to a computer? If not, go to https://pinouts.ru ; dig down through power to your brand. Dell and ATX are similar, but enough different to cause a problem. There is a PS/on pin on the main connector. In older Dells (2002 or so) is it gray, and pin #13; in ATX, it is green and pin 16. Ground the correct pin and the the supply should turn on. John

 

[mvs sarma]

If it is mains powered, mostly the bridge diodes( at least one diode of them, would have failed. before powering ON better check the bridge and the High voltage DC electrolytic cap.

the next culprit could be the MosFET switch, if one is used. otherwise the switcher chip itself.

Ensure that these are not having short circuits to input Dc return and then perhaps you can switch ON, by enabling a loop at some pins(try to see the details on the output connector-- detailed by Jpanhalt.) that the PC simulates, as if the SMPS is working on the PC( assuming it is one used for desktop.).

also check the galvanic cap between output common to input dc return or perhaps neutral.

P S: try this link
**broken link removed** for power ON info

 

[ashfaqueahmadbari]

Do you know how to turn the PS on without connecting it to a computer? If not, go to https://pinouts.ru ; dig down through power to your brand. Dell and ATX are similar, but enough different to cause a problem. There is a PS/on pin on the main connector. In older Dells (2002 or so) is it gray, and pin #13; in ATX, it is green and pin 16. Ground the correct pin and the the supply should turn on. John

the link doesn't seem to work, are you sure it's right?

 

[Hero999]

a blown fuse is Symptom for another problem. so it is likely to get the replaced fuse blown again and may be with BANG.

Not necessarily, it could have been a brownout which causes the SMPS to draw more current and blow the fuse, leaving all the other components unharmed.

 

[jpanhalt]

https://pinouts.ru/Power/dell_atxpower_pinout.shtml

This link is the the Dell plug. You can work backward from it. The pinouts.ru was in my browser history and should have worked. I checked the above and it is working.

John

Edit: The original link seems to be working now. Must have been a short outage.

 

[ashfaqueahmadbari]

Hmmmmm...

It seems it ain't that simple to power on my SMPS. Is there a more 15 yr old friendly way to do this which wouldn't require me ripping apart my PC?

 

[jpanhalt]

First a little information:

1) Do you have a metal paper clip or piece of solid wire that is the right size to fit in one of the connector sockets (about 1 mm to 1.4 mm diameter)?

2) What brand of computer and model do you have? If it is home-built, what is the motherboard?

3) How many pins are in the main connector to the mother board? Are there 2 main connectors (usually 16 pins and 24 pins) or just one main connector (20 or 24 pins) plus a small 4-pin connector?

Since you got the PS out, opened it, and fixed the fuse, I think you will be able to get it started just fine without risking plugging it into your MB. But, I would need that information to tell you which pins need to be shorted together with the wire.

John

 

[mvs sarma]

The only 15 year old friendly way is to get it repaired from a local service facility.
It is very risky to handle such power supplies, without proper background, training, testing equipment and precaution. It involves public mains supply and fatal risk.

 

[blueroomelectronics]

Most ATX power supplies need a load on the 5V before they'll turn on.

 

[jpanhalt]

Most ATX power supplies need a load on the 5V before they'll turn on.

That is not my experience. If you ground the PS_on pin, it will start, but may not give much power until you put a load on them. At least that is my experience with Thermaltake (ATX), Antec (ATX), and Dell (DELL!) supplies.

I think the question is whether the supply will "turn on" and not continually blow the fuse. I don't think shorting between the green (pin 16) and either adjacent black pin is beyond a 15-year old. Some members on this forum are younger than that and are doing some pretty nice things.

It is important that s/he not do that to a Dell (pin 16 is com, and there is no green, so there is minimal risk). The other way around (on the older Dimension series and others, it's pin 13, grey) could end up connecting 3.3V to ground and hurting the PS. Shock risk is low in either case.

John

 

[spuffock]

Give the health and safety inspector a fit of apoplexy. Get a 100W mains bulb and solder a pair of croc leads to it. When you get a blown fuse connect the bulb across it and switch on. If it lights brightly, then it was going to blow the fuse. It shold flash and then burn dimly. After replacing a switching transistor, this test can be useful. If the bulb lights brightly then it was going to blow the transistor again, and you get another chance to find out why.

 

[aljamri]

it happened during a power spike when my UPS wasn't connencted.

For spikes, a component called surge suppressors ( If I recall ) is fitted on the mains input, looks like ceramic capacitors, this may got short and cause simmillar to your problem. use multimeter to check them, if in doubt remove them ( for test only ) to make sure and replace them for further spike protection