ASUS P5A and P2B-S recapping. Searching old datasheets.

[P4C800]

Hi,

I'd like to recap some of my old mainboards (they are from 1998) before switching them on again for the first time after many years in storage. All caps still look good from the outside.
There are three mainboards:
- ASUS P5A rev 1.04
- ASUS P2B-S rev 1.03 "Rubycon"
- ASUS P2B-S rev 1.03 "Chemi-Con"

If you are interested in their specs, The Retro Web has pages for the P5A and the P2B-S.

They all have many 1000uF 6.3V 105°C capacitors. But there are some differences I cannot figure out.

P5A
The P5A only has Rubycon 6.3V 1000uF YXG 105°C capacitors with a diameter of 8mm. But there are two different heights: most of them are about 13mm high but two of them are about 21mm high. I doublechecked but still the writing on all of them looks the same. Now I am wondering: what are they? In the Rubycon datasheets I am finding the 1000uF 6.3V capacitors are 8mm in diameter and 16mm high. So they are different from the ones I have - so do I need an older datasheet? Where could I get it? Although the datasheets always write "standard size" over the tables. Does anyone know about non-standard-sizes? My thinking is they would not bother using two different types if the differences were not important. So maybe they are different ESR or something? As far as I can see using the bigger ones in all places would not cause any mechanical issues so that should probably not be the reason.

P2B-S "Rubycon"
Same questions as for the P5A. Even the manufacturing date on the caps are matching (If I interpret the T9850 printed on them correctly). Still the same two different sizes, though.

And then there are four more caps I'd like to replace. They look like regular radial ones, but the writing on the mainboard calls them CT41 and so on (instead of CE1 and so on) for the electrolytic ones. Also other SMD-capacitors on the board that look like tantalum capacitors have the CT-numbering. So I am suspecting they are tantalum capacitors. They are from Stone, 100uF 16V 105°C 6.3mm dia, 8mm high. However I cannot se any vents on them, so maybe they do not need replacement? Does someone know which series they could be?

P2B-S "Chemi-Con"
The 2nd P2B-S is different in the caps they used. Here the Rubycons are replaced by Chemi-Cons. The small ones are replaced by the LXZ series (12.5mm high, purple-ish blue), the datasheet I could find says they should be 15mm high. So again: do I maybe need an older datasheet? The taller ones were replaced by some from the TM-series (19.5mm high, brown). However I can find no info at all about the TM series. Still I am thinking they are Chemi-Cons because they have the same chemi-con-logo-outline printed on them as the LXZ-ones have. Does anyone know anything about them? Also this reinforces my suspicion that there are important differences between the two sizes.

First: thanks for reading all of my text! Maybe someone can answer some of my questions?

[Per Hansson]

Re: ASUS P5A and P2B-S recapping. Searching old datasheets.

Why would you replace them?
If they are from reputable brands they usually lasts a long long long time...

[stj]

Re: ASUS P5A and P2B-S recapping. Searching old datasheets.

i would stand back for a few minutes the first time those boards are powered - i'v had a couple of rubycon MCZ's explode after years of storage,
but if they dont blow then they are probably good

[Topcat]

Re: ASUS P5A and P2B-S recapping. Searching old datasheets.

Given the series of the caps in these board, they won't need to be recapped. None of those are problematic series. Of course you can if you want, but I don't see the need....just my 2 cents.

The P5A and P5A-B (the AT version of the P5A) are great for retro gamers. One of the few super 7 boards that have AGP's.

[P4C800]

Re: ASUS P5A and P2B-S recapping. Searching old datasheets.

Thanks for all your replies. Is there any chance you haven an estimate how long these caps will still last until they dry out so they need replacement?

My process of thought was that even good brands would dry out at some time so now would be a good time to replace them, as now they at least probably need some self healing. But I'll try turning them on carefully just a few seconds at first to help them a little. Or would this be just useless?

Yes, I am quite happy I got the leftover P5A a few years ago :-). I just hope it still runs, I have read some bad things about its reliability. That was another reason I was thinking about recapping it.

Also what do you think about the Stone capacitors that I suspect to be tantalums? I am asking because I found Stone in the List of Bad Cap Manufactureres-thread.

[stj]

Re: ASUS P5A and P2B-S recapping. Searching old datasheets.

pictures of the stones and board area they are in would help

[ChaosLegionnaire]

Re: ASUS P5A and P2B-S recapping. Searching old datasheets.

Thanks for all your replies. Is there any chance you haven an estimate how long these caps will still last until they dry out so they need replacement?

there isnt an easy answer for this, so im just gonna say that the only scientific method here is to pull a random cap from the board, typically one around the cpu vrm zone and test it with an esr meter to see the specs of the cap and see how far off it is. if it still tests in spec, there is no need to recap, really. just solder it back. if it aint broke, dont try to fix it!

I'll try turning them on carefully just a few seconds at first to help them a little. Or would this be just useless?

use a low power/wattage psu to test since it has a low current threshold for tripping. since computers of that era didnt consume much power, a 150w psu should be enough. however, u should use a good branded psu with known good and working short circuit protection to trip the power in case things go wrong.

Also what do you think about the Stone capacitors that I suspect to be tantalums? I am asking because I found Stone in the List of Bad Cap Manufactureres-thread.

that list only applies to wet electrolytic caps. solid polymer caps from those junk brands work fine. solid polymer is just more reliable that even junk brands that once made bad wet caps can make okay and decent lasting caps, so the tantalums are okay too.

[P4C800]

Re: ASUS P5A and P2B-S recapping. Searching old datasheets.

pictures of the stones and board area they are in would help

I took some pictures and attached them sorry for the bad lighting conditions, but I hope everything you'd like to see is visible.

First there is one overview picture of the whole board where I marked the Stone capacitors and then there are four detail pictures, one for each. I hope seeing them from the side is what you wanted to see.

[P4C800]

Re: ASUS P5A and P2B-S recapping. Searching old datasheets.

there isnt an easy answer for this, so im just gonna say that the only scientific method here is to pull a random cap from the board, typically one around the cpu vrm zone and test it with an esr meter to see the specs of the cap and see how far off it is. if it still tests in spec, there is no need to recap, really. just solder it back. if it aint broke, dont try to fix it!

Sounds reasonable! But this is where I would need to get the proper datasheets to know which values would be healthy :-).
These are the datasheets I found:
- Rubycon YXG - but there is only one size in the datasheet. The ones on the boards are either smaller or bigger. So I am not sure how far the values in the datasheet apply.
- Chemi-Con LXZ-Series: bigger in the datasheet than on the board
- Chemi-Con TM-Series: cannot find anything. Not even the series being mentioned anywhere.
Or do you think when they are bad they usually are so much off that even slightly off values in the datasheets won't matter? Although I would prefer even detecting when they are only slightly off but then there is the question of how good my ESR-measurements will be... And I also would like to know (out of curiosity/to learn something) why they used different mechanical sizes from the same series (in case of the Rubycons).

use a low power/wattage psu to test since it has a low current threshold for tripping. since computers of that era didnt consume much power, a 150w psu should be enough. however, u should use a good branded psu with known good and working short circuit protection to trip the power in case things go wrong.

That sounds like good advice, thanks! I will see what I can do.

that list only applies to wet electrolytic caps. solid polymer caps from those junk brands work fine. solid polymer is just more reliable that even junk brands that once made bad wet caps can make okay and decent lasting caps, so the tantalums are okay too.

Good to know, thanks.

[ChaosLegionnaire]

Re: ASUS P5A and P2B-S recapping. Searching old datasheets.

I took some pictures and attached them sorry for the bad lighting conditions, but I hope everything you'd like to see is visible.

First there is one overview picture of the whole board where I marked the Stone capacitors and then there are four detail pictures, one for each. I hope seeing them from the side is what you wanted to see.

those are actually liquid filled caps. the reason they dont have a vent is because they are too small to explosively rupture and so they dont need a vent. those small caps typically dont cause issues on motherboards so they dont need replacing.

also the date codes on your rubycon caps indicate they are from 1998 to 1999 which is nearly 25 years old. but its not possible to tell how long they were used and whether they were abused temperature wise. however, computers of that era typically run cool with 15-30w tdp unless there was a cooling fan failure which caused unnoticed overheating.

however, yxg is a long life 3k-6k hour cap series when typically most caps of that era were rated to last only 2k-3k hours. so they dont need replacing unless u get problems with the computer in stress testing or u observe signs they are leaking underneath from the bung. the rubber bung on caps can degrade after 15 years as thats the typical lifespan of rubber which comes from rubber trees and is a bio-degradeable material.

Sounds reasonable! But this is where I would need to get the proper datasheets to know which values would be healthy :-).
These are the datasheets I found:
- Rubycon YXG - but there is only one size in the datasheet. The ones on the boards are either smaller or bigger. So I am not sure how far the values in the datasheet apply.
- Chemi-Con LXZ-Series: bigger in the datasheet than on the board
- Chemi-Con TM-Series: cannot find anything. Not even the series being mentioned anywhere.
Or do you think when they are bad they usually are so much off that even slightly off values in the datasheets won't matter? Although I would prefer even detecting when they are only slightly off but then there is the question of how good my ESR-measurements will be... And I also would like to know (out of curiosity/to learn something) why they used different mechanical sizes from the same series (in case of the Rubycons).

those are custom order sizes requested by the board manufacturer. just follow the can sizes and ignore the voltage and capacitance values. for liquid electrolytic caps, their esr and ripple values are dependant on their can sizes. notice the same can size but for different voltages on the other tables all have the same esr and ripple rating with the same can size?

u also seem to be experiencing some sort of "measurement error" with your measured cap sizes. it can be difficult to measure caps still on the board with a ruler so i recommend measuring tape instead. i have some paper measurement tape from ikea which is great for measuring things on the board without shorting things out as its paper. what measuring instrument are u using to measure the dimensions of the caps?

u should use a good branded psu

just to clarify what i said, i said use a good quality branded power supply, preferably with japanese caps inside as well. that is it for now.

[P4C800]

Re: ASUS P5A and P2B-S recapping. Searching old datasheets.

those are actually liquid filled caps. the reason they dont have a vent is because they are too small to explosively rupture and so they dont need a vent. those small caps typically dont cause issues on motherboards so they dont need replacing.

Yes, I also suspect that these are wet capacitors. Although they could also be wet tantalums. However I hope this is not the case as the linked article says they are expensive and unusual for consumer applications. So in that case the markings on the board would just be misleading.

however, yxg is a long life 3k-6k hour cap series when typically most caps of that era were rated to last only 2k-3k hours. so they dont need replacing unless u get problems with the computer in stress testing or u observe signs they are leaking underneath from the bung. the rubber bung on caps can degrade after 15 years as thats the typical lifespan of rubber which comes from rubber trees and is a bio-degradeable material.

I agree, if I would observe stability problems this I would definitely consider replacing the caps as one of the first things to do. My concern is that I could have bad caps where you cannot see the damage and that this would cause permanent damage to other parts of the board. And this is what I am hoping to avoid.
I read somewhere that good quality caps usually use EPT (Ethylene-Propylene Terpolymer) instead of natural rubber. So I hope that means they degrade a lot less.

those are custom order sizes requested by the board manufacturer. just follow the can sizes and ignore the voltage and capacitance values. for liquid electrolytic caps, their esr and ripple values are dependant on their can sizes. notice the same can size but for different voltages on the other tables all have the same esr and ripple rating with the same can size?

Yes I realized that the same size usually results in the same ESR :-). However I was not sure whether they maybe did some more significant changes in the series and this was why they now have different sizes. But the information that there are custom sizes for the board manufacturers is really helpful, now I am confident in what I have to look for. Thanks a lot!

u also seem to be experiencing some sort of "measurement error" with your measured cap sizes. it can be difficult to measure caps still on the board with a ruler so i recommend measuring tape instead. i have some paper measurement tape from ikea which is great for measuring things on the board without shorting things out as its paper. what measuring instrument are u using to measure the dimensions of the caps?

I use some calipers, so the diameter measurements should be fairly accurate. The height measurements however could be a little off, as I just measured the height from the surface of the board to the top of the capacitor. So my numbers could be a little to big.
Also I took care to not short anything out nor scratch the board during my measurements :-). It is powered down for some years now and not plugged in, so there should not be any remaining charge which I could short out. Except maybe for the CMOS-battery which I made sure to not be leaking. Still I should remove it as it is probably dead anyways.

[прямо]

Aren't you supposed to remove the CMOS battery if you want to put the board in storage for a long time? This way there won't be any voltage present on board, especially for the sensitive CMOS and BIOS circuit. Most people don't pay attention to it. They think, oh it's only 3V, what harm can it do?

Better if you can also stuff the board inside a sealable/ziplock-able static bag to protect it from the environment.

[stj]

lithium coincells dont leak - and 3v is only a problem if you let the board get damp
obviously it's a waste of a battery - but it wont harm anything