Yellow caps with F logo and K vents

[willawake]

KC8 revealed some interesting info recently which suprised me since i have apparently mistaken these little yellow bastards as good caps. I saw one slightly bulging on an asus cusl2-m board and so recapped it to be sure as i was not sure it was bad but did not want probs in the future on an office computer.



little yellow bastards in rather superior company on an Intel D875PBZLK (my main system). Why put them there when they could have saved money not using the ultimate cap the Rubycon MCZ and instead put all Rubycon ZL.

'

them again on an asus gf fx5600.



here is that cap off the CUSL2-M. very slightly bulging.

can we get an ID on these caps. KC8 said they might be Fairchild but an extensive google has not brought success.

[Chris1992]

Fairchild I think. I have 1 bulging slightly on my Dell Dimension 8300. Nichi's everywhere else.

[bushytails]

"SWCON" also uses K vents... don't know if they're good/bad though. have a crap power supply full of them, but the supply failed after only a few months, with no caps buldging.

--Randy

[bushytails]

The shaded semicircle on the board is usually negative, right? could those caps be in backwards? (looking at the middle picture)

--Randy

[willawake]

another good example of board stencils being wrong. shoot the designers.

if you also look at the MCZs, the second and third from the top, looks wrong there also.

anyway, well spotted...i am sure that they had fun at the factory.

[AK0R]

Caps installed backwards?

Before deciding that the caps are installed correctly, and that the stencil is wrong, it would be a good idea to ohm out the board with the caps removed (since they're going to be replaced anyhow). Because these are generally used as filter capacitors, one side should be connected to ground. It's easy enough to measure each of the two pins to a known ground, and determine proper orientation. The low voltages & currents and short test times used in PC board test systems generally aren't adequate to identify caps that have been installed with reverse polarity (based on years of board test experience at HP and others). You never know, someone could have just been having a bad day , or worse, loaded them backwards deliberately .

[AK0R]

Fairchild (Fairchild Semiconductor) is a well-known and established name in digital and analog electronics. They don't make passive components, such as capacitors. More than likely, it is some company that doesn't know or care that Fairchild uses a similar logo, or worse, they are trying to pass their product off as being from a reputable manufacturer, similar to the Rulycon (crappy) identifier being "almost identical" to the Rubycon (quality) identifier.

[Chris1992]

Interesting AK0R, I googled for fairchild and found Fairchild Semiconductor. "More than likely, it is some company that doesn't know or care that Fairchild uses a similar logo" I think so after browsing Fairchildsemi.com.

[willawake]

AKOR : you seem to be the guy that could answer why the board stencils generally have some SMD caps marked as C01, C02 etc and some as CB01, CB02. What is the significance of the CB caps?

[Neo2_000]

Electrolytic? or not?

In the middle picture above - the naked surface mount tin cans. I think I saw these referred to in a catalogue as Solid Polymer Caps or something similar.

I had always just assumed that these were another type of electrolytic capacitor, but perhaps not. (It would explain why they are not vented)

If not, could these then be ruled out as a potential source of failure or are they also vulnerable?

Thanks,
Neo

[AK0R]

AKOR : you seem to be the guy that could answer why the board stencils generally have some SMD caps marked as C01, C02 etc and some as CB01, CB02. What is the significance of the CB caps?

There can be several different reasons:
1. The "B" can denote a specific function (such as bypass).
2. They are a different type (e.g., tantalum vs. aluminum oxide).
3. They are placed by a different "pick and place" machine.
4. They ran out of device numbers (usually, no more than three digits after the letter).

Universal standards dictate certain conventions (R for resistors, C for capacitors, L for inductors, D for diodes, U for integrated circuits, etc.). Beyond that, it's up to the individual designers and manufacturers. For instance, Abit uses EC for electrolytic capacitors.

[willawake]

AK0R : many thanks for the info

the naked surface mount tin cans

Neo2_000 : it is pretty difficult to tell the series from the info on the top of those kinda caps. Pictures on several manufacturers sites indicate that they are aluminium electrolytic but their size indicates otherwise. Probably they are polymer caps.

i got a result on the search : FUJITSU RE series solid electrolytic capacitors with functional polymer cathode!!!
http://edevice.fujitsu.com/fmd/en/products/fpcap/

[Neo2_000]

The data sheet describes them as Solid Electrolytic Capacfitors with Functional Polymer. What are we to make of this?

Only one way to be sure - take the Mythbusters approach: Cut one up to see what's inside!

Thanks,
Neo.

[willawake]

Polymer cathode capacitors replace the wet electrolyte in aluminum electrolytics, or the MnO2 cathodes of tantalum capacitors, with conductive polymers.

hmmm....shouldnt bulge then right?

[willawake]

inside its aluminium foil separated by a very thin layer of material which is like paper made from ash. all very dry anyway.

before anybody also starts cutting caps up, please clamp the cap in a vise in order to cut it. there is clearly potential for cut fingers (not for me this time heh)

interesting article for background info on polymer caps


Interesting bit:
Although typical Solid Polymer Aluminium capacitors are inherently reliable, they have a wear out mechanism. Entrapped moisture from during manufacturing causes a steady increase in ESR. The new 125oC ones in the article are manufactured in a manner to avoid this moisture

[Neo2_000]

Way to go Willawake.

Thanks for the great Info.

Neo.

[HyperYagami]

I'm kinda lost here...please forgive me.

So the yellow "K" (Fujitsu RE?) ones are made of Polymer? If so why are they bulging, I thought only the traditional ones do because of the bad electrolyte ...

[kc8adu]

they take on water through the seal and the esr rises.then gas pressure builds and they bulge.
good polymer caps are epoxy sealed .

[BluBlur]

Re: Yellow caps with F logo and K vents

Looked at some Asus (server) boards, some have this same yellow caps on it.

And many old boards have this same one buldging.. not a good sign.

[kc8adu]

Re: Yellow caps with F logo and K vents

Looked at some Asus (server) boards, some have this same yellow caps on it.

And many old boards have this same one buldging.. not a good sign.

have had a rash of a7v with the edge mounted vrm that has a bunch of these.spontainious reboots,lockup,ect.replacing these yellow polymer caps cures the problems.