PSU dead. Help me fix it.

[twanto]

Hello forum,

I have an Athena power 500w PSU that blew with a *pop and some smoke the other day. It may have had something to do with a power spike, or a bad capacitor. I'm not sure. I'm learning as I go along here, and I would like some tips on how to fix a dead power supply. From what I can observe so far, there is one bad capacitor, a 16V 3300uF one, on the low voltage side. Additionally, one inductor on the small circuit board attached to the AC input was busted from the solder joints leaving a bit of discoloration on the CB. I'm guessing this is the origin of the smoke and pop.

I can easily resolder the inductor back in and replace the capacitor, but I'm wondering if that will be enough and if anyone might have any tips as to where to check next for problems. I have a multimeter handy, but I'm not really sure what to check with it.

I have a Corsair PSU on the way and that is what's going into my system, but I would still like to tinker around with this and see if I can fix it. So any help is appreciated. Thanks.

 

[altazi]

Hi Twanto,

I assume you have some familiarity with electronics, based on your comments above. Let me preface the following statements by saying that I am an electronic design engineer with almost 30 years of experience.

First, for general safety, I should mention that I do NOT recommend that anyone muck about in the innards of their PSU, since potentially lethal voltages lurk within. The capacitors can hold their charges for many hours after the supply was switched off or unplugged! So, PLEASE do not attempt any further repairs unless you are an adult, are VERY familiar with electronics, and feel comfortable working on circuits having lethal voltages.

Now that the safety speech is out of the way. . . First, it may not be practical to attempt to fix the power supply. It is almost certainly faster (and possibly even cheaper) to buy a new power supply than to fix a dead one, and in general, troubleshooting any electronics is often very difficult when one doesn't have a schematic. With these conditions in mind, this is something that I would attempt only if I had a lot of spare time, and ready access to a well-stocked "junk-box" full of electronic components.

Is the supply totally dead, or are some of the low-voltage outputs operational? You could re-solder the inductor, and try another capacitor. Just about any junk-box electrolytic cap would be OK for a quick check, i.e, just seeing if the supply is "alive", as long as it meets or exceeds the capacitance and voltage specs. For real operation, this capacitor is almost certainly (or should be) a low-ESR, high-ripple capacitor that is designed for PSU operation; this is not something you can just grab at Frys or Radio Shack. DigiKey is your best bet.

WARNING! Do NOT power-up the supply without some kind of shield between you and the supply. Capacitors can fail violently, and semis can vaporize. Wear safety glasses. Also, it would be better to power it up with it NOT connected to anything you care about, e.g, a motherboard.

Altazi

 

[jsc]

I really do not want to sound like a smartass, but anyone who says: "I have a multimeter handy, but I'm not really sure what to check with it." does not have enough experience to poke around inside a dead PSU. OTOH, that is how you learn.

Your first problem is that there are lethal voltages present inside the PSU.

Your second problem is going to be testing it. Are you prepared to plug a PSU that is known to be questionable into a working computer? You can fabricate inexpensive test loads for 5 and 12 volts out of 6 and 12 volt automotive lamps, but still ...

Your third problem will be parts. There are a lot of really specialized parts in there. Outside of mail order (Mouser Electronics, Texas comes to mind), your best source will be cannibalization from another PSU. That raises the possibility of using questionable parts for the repair job.

I have more than 45 years of electronics experience starting from my teens as a hobbyist working on vacuum tube and transistor equipment to modern military computer and radar equipment, and I just do not regard trying to repair a computer PSU as a productive use of my time. OTOH, if my Antec ($100 on sale) ever died, I might rethink this.

If you still want to do this, Google "computer psu repair" for more information. For your safety, I recommend building a three wire extension cord using a GFCI ac outlet. That way, even a small short (milliamps) will cause it to trip and kill the power to the PSU.

 

[jsc]

Hi, Altazi.

We posted nearly simultaneously. I guess great (or at least competent) minds think alike.

john

 

[twanto]

Thank you both for your responses. You are correct, I don't know too much about electronics, but I am trying to learn. I am aware of the dangerous voltages lurking in the capacitors. The PSU has been dead for a few days before I opened it up. I have no intention of plugging this into any of my components when I replace some parts. I plan, as you suggest, to make a test load from lights. I learned Radio Shack or any nearby computer store doesn't have any parts I would need today when I went shopping. I am a far cry from plugging this thing into a hot outlet.

Thanks for the suggestions about where I can get components. It will definitely be mail order. I have an article about PC PSU repair that claims it can be fairly easy, but it is a bit technical. I am expanding my vocabulary reading it though and can understand some of it. It is also about 10 years old, and while I know some things haven't changed, other things must have. I can easily identify the high and low voltage sides, I think I know where a 12v rectifier is located as well as the 5v rectifier. I've checked the resistence across several capacitors and inductors.

This was a $90 PSU and it would be nice to have it fixed. I'd also like to learn about this stuff. As I said earlier I'm getting a replacement for it and that's going in Monday, but I still want to try and fix this thing if possible.

Thank you again for the responses and safety tips. They are very helpful. Also, I like the GFCI idea.

 

[altazi]

Hi, Altazi.

We posted nearly simultaneously. I guess great (or at least competent) minds think alike.

john

I think I'll go with the "Great". Merely settling for "competent" just doesn't seem to do it for me

This whole PSU mess came home to me a couple of weeks ago. I have one of those 12V thermoelectric coolers for use in a vehicle, along with a 12V 8A power supply so I can use it indoors. The power supply output capacitor failed "extravagantly", blowing its electrolyte out through the cooling vents and onto my living room floor. Talk about smell (!!!!!!)

I took it apart - it was obviously a cheap junk power supply - not even an integrated circuit to be seen. The capacitor wasn't rated for high ripple - hey, it might have cost an extra $0.20, right? When I get up enough other parts I need, I'll order a better, low-ESR/high-ripple job (designed for switching supply output stages) from DigiKey for a couple of bucks. I'll spend about 30 minutes on something like this - any longer, and it isn't worth my time.

Still, I surely get sick of cheap junk - it seems to be proliferating! Curse the corporate bean-counters and cost-reduction plans! Doesn't anyone make anything of any quality anymore?

Regards,

Altazi

 

[phantom93]

i dont mean t oruin anuything goin on here but if ur warrenty is still active cant u just replace it?

 

[twanto]

i dont mean t oruin anuything goin on here but if ur warrenty is still active cant u just replace it?

It's a few years old, do you think my warranty should still be active?

 

[valis]

warranty could be 1 year, or up to 3 years, you could get lucky. that's your best solution really. the time, expense in parts, and the fact that whatever you do to it might not make it work again makes getting another one just the best option, hopefully it's under warranty

 

[altazi]

Hi Twanto,

You weren't over-taxing the 500W PSU's capability, were you? Also, did you have your machine plugged into a surge protector or UPS that, in turn, was plugged into a properly-grounded AC outlet? If not, I highly recommend that you do so when you put your system back together with its new PSU.

If you did have some kind of AC line protection, the UPS/surge protector companies often guarantee equipment that is damaged by spikes, etc., while plugged into their products. Of course, it probably takes a lot of runaround to get them to pay in a case like that.

Regards,

Altazi

 

[twanto]

Altazi,

Thank you for your response. First, I was certainly not over-taxing the PSU, at least at its rated wattage of 500W. I was taxing the computer by running oblivion, but I have logged many hours on that game and many other graphics and cpu intensive games with this power supply.

I did have it plugged into a Stratitec surge protector, it was grounded and protection was active. Either a surge somehow got past it, or a failing component within the PSU caused it to blow, or some combination of the two. As I mentioned above, I know that an electrolytic capacitor was leaking in the PSU, so that may have caused the failure or its inability to cope with a small surge that the surge protector let through. I do know that some surges are too large to be stopped by surge protectors, but from my knowledge those are mostly in the category of lightening strikes. It was a sunny day, so I am perplexed why the surge protector would not work in the case of a surge caused by an AC unit, for example. In any case, I have contacted the surge protector company and they said they would mail me paperwork to start the claim process. I'm sure I will be in for a lot of runaround, like you say.

Also as per another persons suggestion, I did contact Athena Power to see if they can repair my PSU even though I doubt it is under warranty and I no longer have the receipt for it. I'm waiting to hear from them.

 

[altazi]

Hi Twanto,

I wouldn't expect a secondary capacitor to blow as a result of a spike on the powerline, unless the surge event was truly catastrophic. Most surges destroy components like semiconductors, which have relatively sharply-defined voltage limits.

I would guess that your capacitor blew because it was stressed - it might not have been the highest quality of capacitor. Lesser quality capacitors, especially in such a high-current location as a +12V rail in a PSU, could stress out and fail. Also, capacitors do suffer from aging, where their overall capacitance drops over time. Some of the PSU sizing tools let you account for this when you are trying to determine the appropriate size of PSU for your system. A PSU that was "on the edge" when new, could fall into a "heavily stressed" category after a few years, in a worst-case scenario.

I don't know about Stratitec surge protectors, but well-designed units have a UL1339 (IIRC) 330V clamp limit voltage; higher is bad. Fast clamping time (under 1ns) is good. Also, the higher the joule number, the better; this indicates how much surge energy they can safely absorb. These units typically have some kind of indicator that lets you know that the protection circuitry is functioning properly.

A few years back, I had a computer running while plugged into a surge protector. Elsewhere in town, the electric utility accidentally dropped a live 56kV powerline onto a 13.8kV powerline, and my surge protector literally blew up in a shower of sparks. The computer, however, was still fine. In this case, it was pretty evident that my surge protector was no longer "happy".

In this utility accident, I also lost a number of other items that weren't plugged into surge protectors. I now have almost every electronic item I own plugged into surge protectors or UPS units, which include the surge protection function.

Regards,

Altazi