Asrock k7s8xe+ flaky Vcore

[gonzo0815]

Hi all,

i use an Asrock K7s8xe+ mainboard with a AMD Tbred xp 1700@2000Mhz.
The vcore of that board was alway very unstable, right from the beginning.
I thought that this is due to cheap 2 phase vrm circuit, and for more than one year my system wennt well wit a little overcloking and some higher vcore.
But now the system isn`t prime95 stable anymore. In Speedfan i can see that the vcore drops from 1.75v down to 1.65v sometimes. And just then i got the errors in prime. The k7s8xe+ has only 4 3300uf/6.3v KZG capacitors as output filter and 4 1500uf/ 6.3v KZE inputfilter. Now, as i could`t find any other cause, i think those caps dgraded a little and thus the voltage drops.
What do you think about that?

I know, that this board is darn cheap, but i love the sis 748 chiset and all in all i will recap it, if could get suitable caps, which is very dificult in Germany.
So, the KZG have 13m Ohms ESR, hard to beat. And, for teh fact, that the Vcore was right at the beginning very unstable, i wish to find some caps with lower ESR, so i could reduce the vcore further, if the vcore would improve.
The KZG, as far as i know are not bad caps, so the Rubycon FC or FM series aren`t suited very well for this board due tho the higher ESR or not?. May be Samxon GC will do the job, but GA series would be far better....
I use an FSP 350w PSU and tried an Enermx 353w and an Seasonic ss400FS. So i this case, the motherboard musst be the fault.

[MD Willington]

Re: Asrock k7s8xe+ flaky Vcore

Those boards are actually quite decent, they prefere a very good power supply, some people experience weird problems with the cool n quiet bios implemented.

A very good link for Asrock mainboards is here: http://www.rhcf.com/sis-bin/ultimate...forum/36.html?

They even have modified bios for the board.

MD

[gonzo0815]

Re: Asrock k7s8xe+ flaky Vcore

Thx,
i already reflashed the Halt@idl or Cool Bios with the latest ofiziall. This put`s an extra strain not only to the PSU, to the vrm circuit to.
As for the PSU i`ve use 350W Fortron, an Seasonic SS400FS and the above mentioned Enermax EG365AX-VE. All of them have espeziall high combined power rating. And since i use that board, i havent chaned anything.

[MD Willington]

Re: Asrock k7s8xe+ flaky Vcore

I'm running the SiS748 chipset on my mainboard too (M848ALU V2.1)... I have seen the same Asrock boards as yours with failing capacitors on ebay auctions. If the board is working well for you, I would go ahead with replacing the capacitors. As far as which to use, I'm not quite sure for a two-phase setup, some of the more experienced members may know.

MD

[gonzo0815]

Re: Asrock k7s8xe+ flaky Vcore

Yes, the problem of those Aseocks are IMHO the input filter caps and the outputfilter caps due to the poor 2 phases. The input filter caps must sustain an 7A riple current for an 30A autput. Now, Asrock uses 2 x1500uf 10x20mm KZE caps per phase. They have an ripple current of 1820mA and an ESR of 0,023ohms. In my opinion that is a litle bit to close to the limit, as i know that an Athlon XP has an TDP of 68 -70w. At the moment i can only obtain Panasonic FC series or Chemi con KZE. The only improvement i can do so far is to use the KZE 10x25 6,3V 2200uF type, which has higer riple current rating of 2150.
The FC are no choice due to very low ripple current rating of only 1444mA and higher ESR in the 10x format.
For the outputfilter caps i can`t get any suitable replacement in the 10x diameter and spaces for an 12,5x ones are not there.

So the major problem is the avaibility of good low ESR caps in Germany. Most stores even don`t know about Low esr. Even the standard caps are realy crap brands. I hope that big pope can sell me some of the nice Samxon GC series, that would be great.
In any case, i think if i find no other source i only replace the input filter caps an hope to solve the situation an little.

In the mean time i increased the vcore a bit further, that allows stable operation (prime95 stable), but put`s more stress on the caps......

At the moment i consider buying an ESR meter, i can get on for 40€ as an DIY kit. So i can see if those KZE and KZG caps holding the promise, the paper are stating.
If not i consider to replace them with FC ones.

[doggyfreestart]

Re: Asrock k7s8xe+ flaky Vcore

You can easily get Rubycon ZLs from www.farnell.de

[gonzo0815]

Re: Asrock k7s8xe+ flaky Vcore

Yes, but farnell want`s an 50 or 100€ minimum order, and most Low esr Caps aren`t in the europe stock. So aditionaly USA shiping fee makes things worser.
And the main problem is, that the 2 phase desing of that motherboard is designed for an output ESR of 0.0024Ohm. Unfortunately Asrock decided to reduce component count and take some speciall low ESR high uf caps. To obtain similar results on that board, i never ever can increase the ESR of those caps higher than 0.013 ohms, ZL are 0.022 ohms. In fact the recomended desing from st (they make the L6917B PWM chip) used 5 x 2200uf MBZ rubycons. with even lower ESR (0.012ohms) than the Asrock used 3300uF KZG ones. But anyway, i orderd some MCZ Rubycons for inputfilter, and some oscon polymer 2700uf (2,5v, 0,010Ohm) caps for outpufilter. due to the fact that all 3300MCZ are sold out, and no MCZ with lower ESR than 0.012ohms are availibale. So i think i reduced the ESR close to the desing manual from ST.com and lowered the bulk capacity not to mutch. Of course, an mcz with 3300uf or an Samxon would have ben the better choice.
Now i have to wait til they arive.

To make it clear, the board is runing fine @stock speed, even if the flaky vcore are there. But at the moment a Athlon XP well under 2GHZ makes for me no sense.
You can´t compare that Asrock desing with typical older sockel A motherboards, where large banks of low ESR caps are used. For those units e.g 8rda+, k7s5a etc. any low esr cap is suitable, as the desings and the space had ben desinged for the higher esr ratings of the used caps (e.g.in most cases 3 or more phases).In case of k7s8xe+they din`t even left space for more cpas like some other manufacturer dos. They have planed right for the begining to let vcore unstable. Mey be the ucc KZG hase been degraded with the time, so that they now have an even higher esr. In that case i think with that replacement i could lower the vcore, if the drop will be far lower than at the moment.

[yanz]

Re: Asrock k7s8xe+ flaky Vcore

i my self have been thinking a lot to get me an ESR meter or LCR meter. That would help me to check if the caps still have their capacitance and ESR..

KZG afaik is still a good caps and i use it for some recapping project, but a certain design like your asrock mobo or troda's mobo (DFI NF2) might not be suitable for this caps.

[gonzo0815]

Re: Asrock k7s8xe+ flaky Vcore

Yes, thas for shure. If Asrock had been chosen to only take on cap more, probably no problem at all. But ok, they are on a budget.

An ESR meter i think is the best thing one could bay, if low ESR caps are an hoby or proffesion. If i can save some money, i will bay one. In Germany there you could bay an DIY kit wit a clear LCD display for about 50€.

[willawake]

Re: Asrock k7s8xe+ flaky Vcore

did you see my review of the evb meter https://www.badcaps.net/forum/showthread.php?t=1287

its great except the case is closed with latches. it would be perfect if it was closed with screws or had a battery access door. anyway an esr meter is useful not only for troubleshooting but for your better understanding of failure modes of the different caps.

its not essential though for repair, easy just to replace all the bad brands, but might help save some money if you wanted to replace only the off spec caps.

doesnt check capacitance though, you would need another device for that. some multimeters have that feature.

[gonzo0815]

Re: Asrock k7s8xe+ flaky Vcore

Yes, that loks good. I think especially for psu test during dust cleaning such an ESR meter would bekome usfull. or for thos Jamicon, Ost and Teapo kaps, wich aren`t always bad. E.g. some Jamicon low ESR caps are in my 350w FSP PSu, and i think they are perfoming not that bad. Right now i could use it to chek those KZG ones on my K7s8xe+ if theyr góod or not. I would chek any new motherboard for bad caps may be. (especially Asrock and ECS ones).....

[yanz]

Re: Asrock k7s8xe+ flaky Vcore

I'm drooling over the pics, Willawake. Nice review!