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Old 04-10-2018, 09:00 PM   #1
John843883
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Default Polymer capacitor confusion.

Hello to all who read this,

Friends PC stopped working and I found this motherboard capacitor at an angle with one of its legs pushed out. Is this a known failure mode for these capacitors? He swears it hasn't been knocked. Wiggling it does confirm that the capacitor body is separate from the exposed leg.

The PC model is ASUS M11AD and motherboard is h81m-a_dp/m11ad/dp_mb.

The capacitor in question has "5KU22 270 16v" printed on it and is through hole 8mm wide by about 10-12mm high (hard to tell exactly without removing it). Not sure about lead pitch as I haven't removed the board yet but 3.5mm seems to be common online (will check before purchasing).

I'm having trouble identifying this particular capacitor model to find its datasheet, is it actually a polymer or some other kind? Can I use a regular low ESR electrolytic or does it need to be this same style?

I've sorted a short list on RS components but there seems to be a varying mixture when it comes to lifespan hours, some rated for 2000 hours whilst others are 5000 (they all appear to be low impedance at 100khz).

So my questions are:
1. Is this a polymer capacitor or some kind of electrolytic? I've read online that there can be hybrids which look exactly the same as regular polymers.
2. If so can I substitute it for a regular low ESR electrolytic?
3. What lifetime hours should the new capacitor have? Like I said many of the polymers I've found have a varying life-hours rating, some much lower than electrolytics.
4. What ripple current ratings should I choose for this application? Looks to be an input filter for the RAM DC-DC converter, its connected to the 12v rail through a diode and ferrite bead and feeds the DC-DC converter next to the RAM slots.
5. The replacement candidates have ESR ratings of 10-12mohm, is this low enough?
6. Do these types of capacitors fail like this often? I've metered a few surrounding silicon devices and nothing appears to be bad.

Any advice for this polymer virgin would be greatly appreciated!
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Old 04-11-2018, 01:30 AM   #2
ChaosLegionnaire
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Default Re: Polymer capacitor confusion.

1. its an apaq polymer. asus luvs using that brand for its mid and low-end boards.

2. NO. the ram *might* become unstable. i've had junk caps make ram unstable on some of my boards.

3. it depends on how long your friend wants to use the board for before upgrading his computer and how long he uses the computer each day. if he only needs the computer to last for a few more years before upgrading to a better computer and/or he only uses the computer for 12 hours a day, then get 2000 hour caps. cheaper too.

if he intends to use the computer till it breaks or he leaves the computer running 24/7, then get the 5000 hour caps.

4. and 5. suitable replacement series are chemicon psc or psf series, nichicon fpcap L8 or NU series, panasonic oscon sepc series.

6. the cap is right next to the dimm slots, so its not uncommon to accidentally bump or knock into them with your fingers when installing the ram sticks. (fat-fingered user error?)

its also possible overheating caused the leg to come off from inside the cap. i've had some caps come off with the legs still stuck to the board when i overheated the cap while desoldering the cap.

its also possible a mosfet shorted and overheated and passed the heat to the nearby cap and overheated the cap also.

lastly, asus marks the polarity in opposite fashion compared to others. so the shaded side of the cap silkscreen circle is the POSITIVE terminal of the cap! take note of the polarity of the old cap and be careful of the polarity when u solder the new cap on!
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Old 04-11-2018, 04:27 AM   #3
John843883
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Default Re: Polymer capacitor confusion.

Using greentext to quote as that's what the cool kids do and I can't work out how to quote only certain areas of text.

>1. its an apaq polymer. asus luvs using that brand for its mid and low-end boards.

Thanks! Found the datasheet now, its a 160AR5K271M08A2C http://www.apaq.com.tw/images/Product/4317440559_SE.pdf

>2. NO. the ram *might* become unstable. i've had junk caps make ram unstable on some of my boards.

Duly noted!

>3. it depends on how long your friend wants to use the board for before upgrading his computer and how long he uses the computer each day. if he only needs the computer to last for a few more years before upgrading to a better computer and/or he only uses the computer for 12 hours a day, then get 2000 hour caps. cheaper too.

if he intends to use the computer till it breaks or he leaves the computer running 24/7, then get the 5000 hour caps.


Well he's a bit of a gamer but always turns it off after use.

>4. and 5. suitable replacement series are chemicon psc or psf series, nichicon fpcap L8 or NU series, panasonic oscon sepc series.

Thanks, I've compiled a shortlist on RS components and will include it with the post. As you can see there is a bit of a stock shortage right now with some of the more desirable caps, looks like I'll have to make a compromise or wait a while.

>6. the cap is right next to the dimm slots, so its not uncommon to accidentally bump or knock into them with your fingers when installing the ram sticks. (fat-fingered user error?)

Well he swears that nothing was touched, the PC was store purchased and still stock.

Out of the caps that are in stock which would be the best bet? The original cap had an esr of 10mohm and ripple current rating of 5.2 amps.

I've put numbers above them to make it easier to pick out. 5 does have a slightly higher temperature rating than the others so maybe that'll offset the 2000 hours a bit, number 2 is 5000 hours but the ripple current rating is 700mA lower than the originals.
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Old 04-11-2018, 05:46 AM   #4
mariushm
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Default Re: Polymer capacitor confusion.

Any of those will work, I'd go with Nichicon or Panasonic.

Ignore the temperature bit, the VRM for the memory won't be hot so the capacitor won't heat up ...

For polymer capacitors, the lifetime is calculated with formula L = Lo x 10 ^ [(Tm-Ta)/20]

So a 2000h@105c cap being warm at 65v all the time will last for 2000 x 10^[(105-65)/20] = 2000 x 10^2 = 2000x100 = 200 000 hours of operation until the capacitor will still work, but will be degraded by some amount (like 20% less capacitance, 10-15% higher esr, stuff like that)
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Old 04-14-2018, 05:22 PM   #5
John843883
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Default Re: Polymer capacitor confusion.

Update: Its alive! Funny thing is the blown cap wasn't actually the cause of the PC problems, it was seemingly running with it half hanging off the motherboard! I guess the smaller ceramic capacitor in parallel to it was just enough to keep the 12v>RAM voltage (1.5v?) switcher stable.

I actually went with the Wurth Elektronik 870135374004 in the end as the ripple and maximum temperature specs were a bit better https://uk.rs-online.com/web/p/products/8392297/

Haven't tried this brand before so only time will tell.

Last edited by John843883; 04-14-2018 at 06:14 PM..
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Old 06-14-2018, 10:10 PM   #6
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Default Re: Polymer capacitor confusion.

Quote:
Originally Posted by John843883 View Post
Update: Its alive! Funny thing is the blown cap wasn't actually the cause of the PC problems, it was seemingly running with it half hanging off the motherboard! I guess the smaller ceramic capacitor in parallel to it was just enough to keep the 12v>RAM voltage (1.5v?) switcher stable.

I actually went with the Wurth Elektronik 870135374004 in the end as the ripple and maximum temperature specs were a bit better https://uk.rs-online.com/web/p/products/8392297/

Haven't tried this brand before so only time will tell.
I have been meaning to try the Wurth brand solid caps, but being solid caps they are much more reliable than cheap unheard of brand electrolytics.
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