Replacing computer ATX SMPS capacitor, need help

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Surajsharma

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I will be replacing a blown-up capacitor on my Corsair VS 550 SMPS. It use CapXon capacitors which I have read is pretty crap. The problem is I don't know much about capacitors. Its been 3 hours reading articles on Internet and some YouTube videos. As far I have gathered information that 'Low Impedance/Low ESR capacitors' need to be used in ATX Computer Power Supply.

I quote from one of the article which says

"SMPS (Switch-mode power supplies) are pretty sensitive to ESR. The ripple voltage on the output is calculated as Vripple=I×ESR. This means that as the ESR of your caps increases so does the amount of voltage ripple. I can't say with certainty the problems cause by ripple voltage".

The capacitor which I will be replacing is one of those huge 400v ones. The existing CapXon capacitor which I will be replacing has specs which says

270 µF - 400v
LP Vent 85°C
(And there is a circle which have 6 dots around the circle and 1 dot in middle) - NEG (it is written outside of the circle)

I also read that there is 'General' usage capacitors (which is not good because it can cause ripple in SMPS) and 'ESR' capacitors. AC capacitor and a DC capacitor. Then I also read that there are 'Polar and Bipolar Capacitors'. I am confused and vague which one should I buy??

P.S: I have attached the link of the pictures of capacitors that I took

https://photos.app.goo.gl/mbMPrzGFrn09gOmn2 (3 pictures in total).
 
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Karadjgne

Karadjgne

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That's a primary cap. Apart from the facts that it's a) CapXon (which you are correct, junk for a primary) and b) it's a Corsair VS (bottom of the line series), something caused that primary to blow. If it's due to age/usage then figure every other cap is the same age/used so has already suffered degradation to a certain extent. If it's due to abuse, it's quite easy to abuse a VS, even Corsair does not recommend the CS/CX/VS for gaming demand rigs, then when the circumstances are repeated you can expect a good chance of repeated failure.

All in all, rescue of that psu is an idea that needs a good amount of consideration, would it be better for you and the pc to repair or replace.

DC voltage is a pure line voltage, DC voltage from a psu/smps isn't. That's a voltage taken from the multiple amounts of peaks per second from ac sine waves. The line (under oscilloscope) looks like a bunch of hills tied together. The ups and downs between the valleys and hilltops is the ripple. If the voltage is supposed to be 12v, it's also ±@5-15mv for a decent psu. If you start seeing 50mv, you can expect issues later as the 12v isn't guaranteed, it can range from @11.8v to 12.2v generally.
Problems caused by voltage ripple are multiple. Everything from unstable cpus (loss of data, shutdowns, bsods etc) to degradation of every other component lifespan, especially voltage sensitive things like motherboards and SSDs, gpus.
 
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Surajsharma

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If I was all keen to replace it then I wouldn't have asked this question
 
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Surajsharma

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I run 2 Desktop PC. My old machine is just lying dormant there eating dust because the case + SMPS that I purchased was a cheap Chinese one and it caught fire during Boot. I already have Corsair VS 550 laying around. The SMPS still works and boots up my PC the problem is when you put a GPU load the SMPS will trip and restart the system. The reason I pinned down was blown up capacitor. All other components look good on Visual inspection. The SMPS is 2 year old and I broke the Warranty sticker long before its Warranty period was over as the SMPS had gathered enough dust which needed cleaning.

It will be powering a Intel Pentium Dual Core Machine with 4 GB of DDR2 RAM and 160 GB HDD with Nvidia GT 610 GPU.
 
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Karadjgne

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Ok, so this then is a project fixer upper, not a primary pc, so any loss is irrelevant. No worries. Just Google 270uf 400v capacitor. You don't have to stick to the 85°C type, you can use the 105°C aluminum solids if you choose to. I believe that cap is a polar (2 prong) not a radial/bipolar (4prong) kind. Nippon Chemicon or Rubycon make good quality caps, but as stated it's a 2yr old VS 550 which is going to be seeing less than 200w loads on equipment that's already older than 5yrs. I'd not be worried about lifetime degradation at this point due to ripple, as there's much more to ripple than just the output of a primary cap.
 
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Surajsharma

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What about Panasonic caps I have heard that they are also good. Regarding capacitor should I go with general usage one or should I got one with less ESR ones?? And what if I didn't find out exactly same caps that I was looking for. I have also seen that some capacitors of same capacitance vary in different sizes, some are small and large with same values
 
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zoltan.boese

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Karadjgne

Karadjgne

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The differing size caps aren't the same. The larger caps are your 'chemical' caps, same as the blown one. The slightly smaller are usually the aluminum caps. Do the same job, the solid caps just do it better, last longer, don't degrade as fast etc. You'll be much better off with replacing all the primary caps with 105°C solid aluminum, as you see, they'll take more of a beating than the cheap 85°C chemicals.
 
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Surajsharma

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I found the capacitors with capacitance value of 270 uF but they are 450 Volts will that be a issue?
 
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Surajsharma

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I see, you know what when I found out that blown capacitor, there was something liquid kinda thing leaking from the top cap, was that a Chemical??
 
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Surajsharma

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xDDD

Thanks mate and I love your profile picture

I will inform you about the results in few days maybe tomorrow or day after tomorrow. Stay tuned!!
 
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zoltan.boese

zoltan.boese

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That voltage number is a maximum what the capacitor can bear. It may be higher than 400. You are good to go with the 450V variant!
 
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zoltan.boese

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I could not open the photos. I presume the capacitor used so called snap in pins, such as https://www.tedss.com/LearnMore/Snap-in-Capacitors
an the component will sit tight. I would not worry about that. There is a standard for pin distance.
 
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Surajsharma

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Is it necessary that a capacitor used in SMPS will be 2 pin or 4 pin and should I get General usage Aluminum based Electrolytic capacitor or Low ESR based Aluminum Capacitor??

And the height of the capacitor is around 4.3 Cm = 43MM
And the diameter of the capacitor is around 6.5 Cm = 65MM

I measured the diameter by a string around the capacitor neck

I haven't made a purchase till now
 
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Karadjgne

Karadjgne

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Here's hoping it's all good. Honestly it's been years since I've seen anyone tackle the job of repairing a busted psu, it's one of those 'throw away' components if the warranty is expired, which doesn't take long. Almost all of the C series corsair has are short warranty, shorter lifespan in a gaming rig, and cheap, so replacement is far less costly in time and effort than figuring out how to fix the old one.

Kudos for the effort!
 
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