Major Caps / Minor Caps ??? Difference?

[PCBONEZ]

In your main discussion you say the only concern is with caps of 1000uf and larger. ~~~ Why?

I don't get it....
Do the smaller caps use different chemicals?

I ask because I have several boards (different makes) where all the 1000uf and up caps are "good ones" (Rubycon, Panasonic, Chemicon, Nichicon) but MANY of the smaller caps on those same boards are Teapo, Tayeh, or some other crap brand.

~ Why are these 'safe' when the larger ones aren't???

[PCBONEZ]

Re: Major Caps / Minor Caps ??? Difference?

Nuther part to my question:

Noting that the smaller caps typically don't have vent 'stamps' in the top of the case,, does the existence of the vent stamp have anything to do with which ones should be replaced or not?

[linuxguru]

Re: Major Caps / Minor Caps ??? Difference?

The smaller caps rarely encounter the same stress (ripple current, temperature) that cause the larger caps to fail prematurely.

[PCBONEZ]

Re: Major Caps / Minor Caps ??? Difference?

So what we are saying is that the smaller caps have the same chemical mix that is prone to forming gases inside the can as the larger ones do?

I'm not trying to be anal, it comes naturally in my case.

... That and I have two boards with and 43 small Teapo's each on them in addition to the bad larger caps.
.

[PeteS in CA]

Re: Major Caps / Minor Caps ??? Difference?

So what we are saying is that the smaller caps have the same chemical mix that is prone to forming gases inside the can as the larger ones do?

If you overstress an electrolytic, hydrogen gas may form. With that proviso, the general answer to your Q is, "Yes." At a finer level of detail, there are something like three different solvents used in lytic caps, ethylene glycol, gamma butyro lacrone and one whose name I forget. Additionally, the ultra-low impedance types have elevated water content (e.g.: Nichicon HD, HE, HM, HN, HZ; Panasonic FM; Rubycon YXG, YXH, ZL, ZLH, MCZ; UCC KY, KZG, KZH, KZE). The latter technology seems to be finicky and more sensitive to ambient temperature. I'd be very wary of ultra-low impedance caps from vendors other than those four (and possibly Samxon); I'm not sure whether Sanyo has parts with that electrolyte technology. As some may point out, there have been problems with Nichicon HM and HN (mfg. process related) and possibly with UCC KZG.

All that said, if good quality electrolytic caps are used within their specified parameters, hydrogen gas formation should not occur.

[PCBONEZ]

Re: Major Caps / Minor Caps ??? Difference?

Thanks. Um, I'm very familiar with the bad caps issue in general. ( I am a retired electronics tech. Fortunately I retired just as the bad caps hit the market. )
- Though I rarely post in the forum I'm a full blown PC GEEK and I've been through the site in great detail. I'm in here frequently myself looking for known problems with some motherboard or another and via Experts Exchange I probably point to badcaps.net as a reference/resource/service 10 or 15 times a month. (I build traffic to you, patting me own back.)

My question [re-stated] was: "From a given 'known bad cap manufacturer, why are the small ones not a concern when the large ones most always are."

It pertains to this post:
https://www.badcaps.net/forum/showpo...86&postcount=4
Where it says:
[[ You should check the list of bad capacitor manufacturers and that will give you an indication of whether your motherboard is a candidate for failure. We are talking about the larger caps which are 1000uf and above, not the minor caps. ]]

Now, I've seen, worked on, or trashed around 2 dozen boards with bad caps so I've seen the failures.

With exception (below) I agree that the small ones don't fail.
~~ I just don't know WHY.

The exception: I see a significant number of posts in the forums with failures of caps less than 1000uf. (Usually 470uf or 820uf.)
- I have noticed from those with pics included that those smaller one that fail DO have the vent stamp which isn't seen on small caps that don't fail.

(I personlly found 4 bad 820uf caps this week which is what got me looking into this.)

~~

Beyond my question as to why that is,

I propose that the existence (or not) of the vent stamp is a better rule-of-thumb / indicator as to classifying the cap is a possible problem than the size in uf.

My bad caps experience is much less than you folks.
Does the vent stamp as an indicator seem valid to you?
.

[gonzo0815]

Re: Major Caps / Minor Caps ??? Difference?

There are several reasons, why the smaler ones are not that frequently failing:

1.on most motherboards, the smaler caps are only used as generall decoupling or may be energy storage caps, to maintain a equal potential on all the supply lines over the whole board.
Those caps are not faced off high ripple currents or rapid discharge & charge cycles, they do therefore do not heat up and in most cases the locations are not near hot components. The big caps on the otehr hand are usually used in VRM units as input or output caps for the small switchers. The heat from the near mosfets and cou is a severe condition too.

2. From reason one we can deduct, that those caps do not have to be ultra low esr caps. Thus the elektrolyt may not contain water. Water is very very corosive to aluminia, wich will cause hudrogen production. The only way to avoid this is nearely pure aluminia (>97,xx%, wich is expensive...) and some not well known inhibitors.
Furthermore, water will evaporate faster. In generall, producing high grad decoupling or generall purpose caps is today not the real hard thing, as those elektrolyte formulas are very forgiving and somhow well known.

3. This site is dealing with premature failure of caps. This is in most cases caused by high water elektrolyt with inadequate additives or not pure enough aluminiafoil. And in some cases bad desing of the board and high temperatures. This kind of failure is IMHO limited to the caps with water based elektolyt from manufacturers with limited knowledge and bad QS. They only bought the raw materials and put them together without an own r&d department.

4. The small caps could be bad too, but on most boards, they aren`t kriticall for the system. As long as they haven`t lost all capacitance. This usually rarely occure, even real bad caps with spoilt bungs & vent`s have capacitance. It`s the ESR wich will rise, but this is not that important for this kind of application.
Tghere is no doubth, that every elektrolytic capcitor will fail after some time, but usually the GPO caps last a long time. This is probably out of the scope for pc systems.
The 470uF and 820uF caps are used in many cases in small VRM units for Vmem or V chip, wich are switching supplies too. Thus those caps are in some cases water based low esr caps. The 820uF caps are often used in VRM output to provide faster transient response fpr the cpu. Thus they are usually low esr and water based.

[PCBONEZ]

Re: Major Caps / Minor Caps ??? Difference?

I follow you.

Would it be safe to say that caps without vent stamps are not low ESR caps??
... Or that they don't use water based electrolytes??
.

[gonzo0815]

Re: Major Caps / Minor Caps ??? Difference?

Probably yes, but the rubber bunge is some kind of safety vent too. Similar with smd caps, they just let the bung out. I have seen that in action as i drived around with the local fire-fighting vehicle and some cheapo SMD caps exploded. They where build into a battery charger. Probably the engineer was not familiar with the different cap lines and the whole quality issue with them. The charger was not a bargain (aboputh 150€ for an 8 cell Fm unit accu charger). I fixed it with some good rubycon SMD`s and since them no problems anymore with this unit.
Fruthermore, the prssure in small caps will not reach that may be dangerous levels due to the limited elektrolyte content.

[PCBONEZ]

Re: Major Caps / Minor Caps ??? Difference?

Okay,

I want to thank you all.

I think from this discussion and some other forum posts I've developed a more complete 'rule-of-thumb' for my own use in determining which caps need replaced.
- I'm throwing it out here in case some else wants to adopt it.

~~~~~

Replace:
All Crap brand Caps with uf 1000 or above.
[and]
Crap brand Caps with the uf less than 1000 'and' the voltage is higher than 10v.
[and]
Crap brand Caps with the uf less than 1000 'and' it has top vent stamps.
[and]
Caps of any brand with obvious bloating, venting, leaking problems. And on THAT board only, all caps of identical mfr/size to those with obvious problems. (To cover for random 'bad batch' manufacturing problems.)

~~~~~

Thanks again for your help!!!
.

[japlytic]

Re: Major Caps / Minor Caps ??? Difference?

Depending on the application, I consider capacitors 470uF and over to be major, and anything under to be minor. Sometimes the minor units cause problems, particularly in audio and video amplifiers.

[gonzo0815]

Re: Major Caps / Minor Caps ??? Difference?

For me, any cap on a GP (generall purpose, e.g. decoupling etc.) position can left there, as long there is no criticall component there (e.g. linear Vmem circuit) and no actuall problems in that region.

Any bad cap on a switcher circuit will be replaced. Any bad cap near a hot component should be replaced.

[PCBONEZ]

Re: Major Caps / Minor Caps ??? Difference?

Now one of my concerns with the smaller caps is simple age.

Why?

I have two systems that were working fine but now won't boot at all. - The boards are 6 years old now but were "new" (unused) when put in. - I doubt they have over 100 hours of total 'up time' in their whole life.

These systems were built about 2-1/2 years ago and used as display systems to loop (play over and over) informational videos for a couple of events. Then they were stored in case I needed them again. Now and then I'd check-boot them to make sure they were working. Last time checked was 4-5 months ago and they seemed fine.

I brought them out last week to dismantle them for parts and when I tried to fire them up to check the parts function before disassembly they wouldn't even boot. - MoBo failure is confirmed now. The PSU, video, CPU, Drives, and RAM all tested good.

Just FYI: The CPU VRM Caps are all Rubycon but there's 'major' and 'minor' Teapo on the rest of the board including by the Chipset, RAM, and AGP slot.
- Some of the 'major' Teapo's are obviously (but not badly) bloated.
(They are 1000uf 6.3v)
- Very low hours. No over clocking. No hot environments. Cases with good air flow. Quality PSU's. (Not the same brand PSU's and not even the same cases.) - The caps that bloated have PLENTY of air space around them.

This makes me think that ~TIME~ (age) has as much significance as loading and heat does for caps with bad electrolytes.
(At least some bad electrolytes.)

These Teapo's were 'major caps' but they apparently died ONLY because of age and two identical boards 'went' at the same time.

This rather kills the "Only major Caps go because of harsh usage" theory.

IF age alone will kill the 'major' caps then it will kill those 'minor' caps using the electrolyte in about the same time frame.

That means -ALL- crap brand caps ARE going to 'go' JUST because of age.

If they are in fact ONLY used for coupling and the actual capacitance doesn't change then that may not be a problem.

- But, *I* don't know why a given Cap is *there* in a given spot on a motherboard and I'm not so confident as you folks seem to be that they aren't sometimes used in ways that could cause problems with data corruption on a board that otherwise (power distribution) runs perfectly fine.

Those caps failed after 6 years with almost no use.

- So, now I'm leery about putting time and effort into any board if it has many 'minor' crap brand caps on it. (I have some boards in my 'fix later' box with well over 40 of those damned things.)

~~~

On any given model of motherboard, I can not -KNOW- if one of the smaller crap brand caps is going to cause me problems later simply due to AGE until it actually gets old and causes problems.
- And I'll first know because of lost data.

That really SUX!

.

[trodas]

Re: Major Caps / Minor Caps ??? Difference?

I think it is very naive to assume the small caps aren't need to be replaced. I encounter various "unexplainable" issues untill I exchange these caps as well, so my statement (whatever SOME may don't like it) is crystal clear:

Always replace ALL electrolyte capacitors on board from known inferior brands.

That include 10uF GCS witch prevent my V266B (sometimes) posting. That include another bunch of 10 and 22uF GSC witch precent DMS monitor off on same board. That include 22 and 47uF Teapos on M810L, witch did bios and statup issues to me as well...

...and finally, exchanging these 470uF Teapos with Samxons GC ones resulted with EXTREMLY BIG SPEED BOOST on my MSI KT6V recap.


There is no question that bad electolyte in both big and small caps do make them fail. Yes, the smaller ones are usually not as stressed and therefore hold longer, but it still become failing sooner or later. Davmax has to recap smaller caps on his Epox 8RDA+ recently too, after experiencing keyboard detection problems and we can continue listing these problems for pretty long...

On the other hand I have yet to encounter one argument about why NOT exchange the small caps. The price is laughably low, any Panny FM/FC will do the job and they are awailable (Digi-key or Big Pope) ...

If you choose problems - choose not to recap them

[kc8adu]

Re: Major Caps / Minor Caps ??? Difference?

i have seen a very few boards that needed every lytic replaced.
99.9% of the time 470uf and up gets it fixed.
most boards that needed all replaced were msi and most were smd which are unreliable anyways.

[Topcat]

Re: Major Caps / Minor Caps ??? Difference?

If you choose problems - choose not to recap them

There you go posting misleading crap again....... Everyone knows this is not the truth, except you....because you're so much more enlightened and intelligent than the rest of us.

KC8 hit it on the head, 470uF and up will cure 99.9% of boards with bad caps. It's been my experience, and everyone else's experience that I know who recap boards.

[Spacedye69]

Re: Major Caps / Minor Caps ??? Difference?

I say changing EVERY component on the board is the way to go. Just changing every smd ceramic and resistor gave me an extra .0001 FPS on BF2 and my 200mmx pentium now folds at 8 units/day!

[Topcat]

Re: Major Caps / Minor Caps ??? Difference?

I say changing EVERY component on the board is the way to go. Just changing every smd ceramic and resistor gave me an extra .0001 FPS on BF2 and my 200mmx pentium now folds at 8 units/day!

Are you serious about changing every cap on the board? I can sense the sarcasm obviously in the 8 W/U's and FPS comments, but it is not necessary nor is just about any board worth changing every cap. If that's your preference, thats cool, but it is not necessary for a successful recap.

[Spacedye69]

Re: Major Caps / Minor Caps ??? Difference?

Thats my point-not needed. It's like rebuilding the entire brake system on your car because your brake pads are worn. If your bored, go ahead, hardly worth it, though.

Speaking of tiny parts, does anyone have any input on brand choice for small ceramics, resistors, diodes etc. or does it not matter?

[Sudum Gumudu]

Re: Major Caps / Minor Caps ??? Difference?

KC8 hit it on the head, 470uF and up will cure 99.9% of boards with bad caps. It's been my experience, and everyone else's experience that I know who recap boards.

What is the consensus in this community when it comes to recapping PSU:s, in order to do the job properly?
Is it enough to do the secondary filtering caps, 470uF and up, or is recapping any other caps in order? I've read that the big primaries seldom fail, so they can usually be left in place, even if they are from a crap cap mfr, but what about other higher voltage caps in the PSU?