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Old 03-28-2019, 08:48 AM   #1
Yakusa
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Default K7S5A recap

Hi.
Board have:
7x2200uF/6,3V
3x1800uF/6,3V

Can i use straight 10x 2200uf like Panasonic EEU-FR0J222B?

This is my weird retro project.

Maybe any ideas about poly cap replacement?
APSC6R3ELL222MJB5T
https://www.digikey.be/product-detai...198-ND/3998084
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Old 03-28-2019, 12:33 PM   #2
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Default Re: K7S5A recap

where are those caps located on the board? are they on the cpu vrm? if so, looking at pictures of this board on the web, the vrm design seems to use a low switching frequency, so no poly-modding. the vrm may not like it. stick to the panny fr caps.

measure the original caps. make sure the replacement caps can fit there. the 2200F 6.3v panny fr caps are 10x20mm in size. if u get the wrong size caps, they wont fit because the caps on the cpu vrm are located side by side with no room if u get the size wrong. if the caps are too tall, they may interfere with the installation of the cpu heatsink as well.
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Old 03-29-2019, 01:00 AM   #3
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Default Re: K7S5A recap

hmm... my ole' K7S5A 5.0 is still in cold storage, haven't used in probably at least half decade after using it for about that much at least.
Mine has all OST caps for the big ones, all 3.3mF/6.3V RLX. Uses an old KA7500C.
Rest of the caps are G-Luxon.

None have leaked as of yet.
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Old 03-29-2019, 02:44 AM   #4
Yakusa
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Default Re: K7S5A recap

@ChaosLegionnaire it looks like this
good info about non poly ones. But question is if i can use all 2200 instead of 2200 + 1800 ones?
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Old 03-29-2019, 05:00 AM   #5
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Default Re: K7S5A recap

i dont see why not if they fit. 2200 may be slightly out of the +20% tolerance band but an extra 40F out wont make a difference.
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Old 03-29-2019, 07:57 AM   #6
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Default Re: K7S5A recap

Interesting, mine has the KA7500 populated in the bottom 16-pin DIP but it's depop in this picture. And mine uses 3m3 capacitors instead of all those 1m8/2m2 capacitors.
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Old 03-29-2019, 09:51 AM   #7
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Default Re: K7S5A recap

Oops. Mine is the K7S5A Pro, which probably explains why they look different. Don't know why that KA7500 placement is there but depop however...
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Old 04-04-2019, 07:07 PM   #8
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Default Re: K7S5A recap

I have a K7S5A here as well.

All the caps next to the CPU on mine (both high side and low side) are G-Luxon LZ, 6.3V, 2200 uF.

Panasonic FR 2200 uF should be absolutely fine for everything. I replaced two of the G-Luxon's on mine with Nichicon HZ, 6.3V, 2200 uF - a bit overkill, but only used two caps just because I didn't feel like doing a full recap and the original G-Luxon caps were, surprisingly still reading normal. So a polymod might work if you use at least 1800 uF polymers... but I frankly don't think it's worth it on this board, as it uses low-speed switching for the CPU VRM.

By the way, are the caps on your board bad or is this just a preventative recap?
If you have problems and the caps are not the issue, try the board with SDRAM instead of DDR. For some reason, mine won't post with DDR RAM at all (gets stuck on BIOS code "D3" on my POST card.)

Also, look up "HoneyX" BIOS and "CheapoMan" BIOS for this board - should unlock some extra options in BIOS, if you are interested.

Last edited by momaka; 04-04-2019 at 07:09 PM..
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Old 04-13-2019, 03:06 PM   #9
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Default Re: K7S5A recap

hey im suprised to see this thread... im in need of info here as well... i got K7S5A v3.1 board in bad shape, caps ware ok, but it was filthy as hell... and it had sempron???? cpu in it...

after cleaning i put athlon 2400 (133fsb) in it (known good) and it turned on... yeee... but it only worked with 100/100 (fsb/mem),
no post with 133/133, which is strange cos in know the board is compatible with 133 and cpu is native 133...
after that i googled a bit and found out its problem with DDR... i god knows i tried at least 10 modules, form pc2100 to pc3200...
tried all moded/OC bioses.. all the same...
tried better psu (this one is known working but i said what a hell...), all the same
after that i put some SDR and turned on, set fsb to 133/133 and it woked WTF???

ok i set to reinstall windows 98... it froze at one moment, but after restart it finished install... driver install went ok....
but upon putting AGP graphic card and installing driver board would work for some time, like 1min or so and then froze...
i tested a lot of different graphic cards from 1X AGP to 8X AGP... all the same problem...

all temps, voltages reported by mobo are ok, but it freezes...
reading from the net i found out that KA7500 regulates voltage for chipset+AGP+MEM... but i dont have spare to change

sorry for long post, but what would you suggest to do?
i was thinking about recapping but i dont have caps now...
should i only recap around KA7500 or the whole board? caps seem ok, not bulged... can i use 3300 6.3v?
i think i have some panasonic, low esr somewhere...
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Old 04-14-2019, 06:57 AM   #10
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Default Re: K7S5A recap

The K76S5A is a shitty board in the first place... poor layout , poor bios , poor everything

The board won't benefit from super low series like Panasonic FR, but you can use them if that's what you have.

Looking at Yakusa's picture a few posts above

The 4 1800uF 6.3v caps tell you the VRM takes 5v from the psu and converts it to lower voltage.
So if the psu outputs a clean 5v, then these capacitors don't matter that much. You can use higher capacitance here, won't matter.
You can also use 10v or 16v rated capacitors if they're cheaper, as long as it's more than 5v.

The six 2200uF 6.3v caps above are in 3 groups of 2 caps.. basically the VRM has 3 phases, and each phase has 2 capacitors in parallel, in order to reduce ESR.

They used 2200uF 6.3v most likely because they were the tallest capacitors they could squeeze there and not affect heatsinks (vertical height is limited near the socket)

You could probably replace them with 1200uF or 1500uF 4v polymer capacitors if you want to. Can probably replace them with FM/FR series 1800uF 6.3v / 10v as FM/FR series probably have better ESR in the first place compared to whatever OST or "who cares" brand ECS used.

For example, tme.eu has kemet 1500uF / 6.3v with 14 mOhm ESR: https://www.tme.eu/en/details/a750ks...acitors/kemet/
4$ for 10 ... could easily replace all 10 capacitors with these instead of FR or FM series
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Old 04-14-2019, 08:33 AM   #11
ala_borbe
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Default Re: K7S5A recap

oh cmon, the board is not that bad... plus i got it for free... it has decent performance, should be compatible, that nice universal AGP slot that can run my savage 4 and voodoo 3 with no problem. i test a lot of old vga cards, some go to collection, some for sale. main highlight is that AGP and both SDR/DDR support

now for topics...
i saw that cpu voltage was stable most of the time, plus i had problems with agp cards and ddr.... so i did not touch that vrm...
instead i replaced 1500uf/6.3v... two near chipset, for near memory slots, two next to agp slot....
put in athlon 2000 palomino core and 2x512ddr
it booted, set to 133
now running aida stress test for 20min.... so this comes as solved
for me guilty ware 8 caps

gona do come oc and some games to make sure its rock solid

tnx for advices
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Old 04-18-2019, 07:44 PM   #12
momaka
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Default Re: K7S5A recap

Quote:
Originally Posted by ala_borbe View Post
oh cmon, the board is not that bad...
Agreed.
It was actually quite a popular board back in the day. And quite reliable, if capacitor issues are to be taken aside.

Quote:
Originally Posted by ala_borbe View Post
i saw that cpu voltage was stable most of the time, plus i had problems with agp cards and ddr.... so i did not touch that vrm...
instead i replaced 1500uf/6.3v... two near chipset, for near memory slots, two next to agp slot....
put in athlon 2000 palomino core and 2x512ddr
it booted, set to 133
now running aida stress test for 20min.... so this comes as solved
for me guilty ware 8 caps
Thanks for posting back your results and keep us updated if anything changes.
So it looks like it was the other caps that were the cause. That's quite strange, as this board uses linear regulators everywhere else. I figured none of those caps would matter too much if they went a bit higher ESR, due to them being used in a linear regulator circuits. But I guess not. I'll see if I can recap my board this or next week and report here as well if I have success with mine working again with DDR memory. Seems that's the only issue so far. It gets stuck on code "D3" with any DDR sticks (and I tried both newer PC2700 sticks and older "compatible" / low-density PC2100 sticks.)

Quote:
Originally Posted by ala_borbe View Post
gona do come oc and some games to make sure its rock solid
Awesome!
What games do you have in mind?

Quote:
Originally Posted by mariushm View Post
The 4 1800uF 6.3v caps tell you the VRM takes 5v from the psu and converts it to lower voltage.
Correct.
It's an oldschool s462 board. And like many of that era, it uses the 5V rail to generate CPU V_core.

Quote:
Originally Posted by mariushm View Post
The six 2200uF 6.3v caps above are in 3 groups of 2 caps.. basically the VRM has 3 phases, and each phase has 2 capacitors in parallel, in order to reduce ESR.
Incorrect on that one.

Although this board does appear to have 3 phases (as evident from the 3 inductors), the CPU VRM for this motherboard is NOT a 3-phase design. The K7S5A uses a single-phase, single-ended buck VRM design for the CPU power. All three upper MOSFETs of the CPU VRM are driven at the same time from the KA7500 PWM chip (though not directly - each MOSFET is driven from a buffer circuit implemented via 2 small SOT-23 transistors next to each MOSFET.) Also, this motherboard's CPU VRM does NOT have lower MOSFETs. It uses free-wheeling schottky diodes instead (a very inefficient and simple design.)

Quote:
Originally Posted by mariushm View Post
They used 2200uF 6.3v most likely because they were the tallest capacitors they could squeeze there and not affect heatsinks (vertical height is limited near the socket)
Not at all.
Those capacitors are way out of the way of any heatsink, so there really is no restriction on the height.

Quote:
Originally Posted by mariushm View Post
You could probably replace them with 1200uF or 1500uF 4v polymer capacitors if you want to.
While 1200-1500 uF polymers will likely work, I do NOT recommend it at all.

Again, this motherboard uses a very primitive CPU VRM design with a single-phase driven from a KA7500 PWM chip. (One could even argue this is just a tiny step-up from a 555 timer driven circuit. ) Because the KA7500 PWM IC has very low switching frequency (less than 50 KHz, likely, if even that), ESR does not matter as much as capacitance does in this circuit. So keeping the output capacitors to what they were originally is recommended. Going higher in capacitance won't hurt. But going lower in capacitance (for example, due to using polymers) may actually increase noise and lower over-clocking abilities (not that this board is known to have any, but still. )

So stick with 2200 uF or higher capacitance on the VRM output / CPU V_core. The ESR is almost irrelevant at the switching frequencies that the KA7500 uses... so any entry-level low ESR caps should work fine too. Though, Panasonic FR and FM are always a nice welcome upgrade. Rubycon ZLH are great too.

Last edited by momaka; 04-18-2019 at 07:48 PM..
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