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Old 02-06-2020, 08:11 AM   #1
kurbeco
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Default Abit KR7A

I have an Abit KR7A with bulging caps near the CPU.

They are Nichicon - 3300uF 6.3v 105c x 5 (10mm dia 25mm high approx) HM(M) - date code; H0140. So even if they weren't bulging, they need replacing because of that date code.

I'm based in the UK and I'm trying to find suitable replacements on CPC / Farnell.

https://uk.farnell.com/nichicon/uhm0...-20/dp/2113082 these are the discontinued caps.

I've seen posts here suggest Rubycon 3300uF 6.3v Ultra Low ESR (MCZ) but these are EOL and the listing in the store says to use 2200uF 6.3v 10mm ZLH Series.

I wanted to double check this as the capacitance is lower.

I can source them from https://uk.farnell.com/rubycon/6-3zl...-20/dp/8127166

but as this is the first time I'm recapping a motherboard, I wanted to check that I'm getting the correct parts.

There are two other caps near the CPU that *look* fine, but as I have a distrust of old caps in areas of the board that would've been hot I think I'll replace those too

rubycon - 4700uF 6.3v 105c x 2 (13mm dia 30mm high approx ) S0052

Looks like I can still get the same caps to replace them; https://uk.farnell.com/rubycon/6-3zl...-20/dp/1144675 unless I'm missing a series number.

Any advice greatly received.
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Old 02-06-2020, 08:20 PM   #2
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Default Re: Abit KR7A

i managed to pull some pictures of the cpu vrm area of your board off the web to study. i attached it to my post. check the image to see if its correct. if its not, ignore what i type below and upload some photos of your board so we can study the cpu vrm area.

since the cpu vrm area uses a very high switching frequency since the coils have only 3 turns, esr matters more than capacitance. the esr of the zlh series is too high, so i recommend polymodding instead.

try to get panasonic oscon sepc series or chemicon npcap psc series 2700uf 2.5v for the caps closest to the cpu. these are typically the cpu vrm output caps. for the caps slightly further away for the cpu vrm input, 1500uf 6.3v poly caps.

i also see that abit likes to use teapo caps scattered around the board for general filtering. they are Y vent caps with three additional notches. those are no good on motherboards. replcae them with panasonic fr or fs series electrolytic caps.
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File Type: jpg abit kr7a cpu vrm area.jpg (93.2 KB, 24 views)
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Old 02-07-2020, 05:21 AM   #3
kurbeco
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Default Re: Abit KR7A

Thank you for your reply.

That photo you've found looks correct. Though my board is an earlier version and has different caps to what you have in that photo. I will attach images.

Does it not matter that the caps nearest the CPU are 6.3v and the replacements you've suggested are 2.5v; and would this also apply to the 2 caps that are between the CPU socket and the ATX power connector (see attached photo)

The rest of the caps look like the Teapo ones you've mentioned - and there are around 40 in total on this board. Are you suggesting it's best to replace them all. That's going to be fun hunting out the correct parts
Attached Images
File Type: jpg IMG_20200128_113948.jpg (1.35 MB, 27 views)
File Type: jpg IMG_20200128_150444.jpg (1.04 MB, 22 views)
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Old 02-09-2020, 06:15 PM   #4
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Default Re: Abit KR7A

ah yes, i did not notice the two caps near the cpu socket by the main atx connector. those are tricky. i dont wanna ass-u-me anything lest things blow up and damage the board.

do u have a multimeter? if so, check for continuity on the positive leg of the 2 caps by the main atx connector with the 3 caps by the cpu vrm mosfets. if its a short, it means they are all part of the cpu vrm out filtering circuit, so its fine to use 2.5v caps there because the cpu vcore voltage of the athlon xp cpu is only 1.6v. even overvolted, the voltage wont be more than 1.7-1.8v so its still fine.

teapos are known not to function well on motherboards. when they fail, u will experience symptoms like usb devices constantly connecting and disconnecting when in use or not being detected at all; memory issues or memory not being detected esp. when u load all 4 dimm slots with memory sticks; bus mastering and ide drive errors; issues and malfunctons with agp and pci cards used in the board; cmos and onboard clock and time not being correct or resetting to the default time many years ago when the board first came out.

these may not be critical issues that stop the board from working but they can be annoying and reduce the enjoyment of operating and using the machine.

Last edited by ChaosLegionnaire; 02-09-2020 at 06:18 PM..
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Old 02-13-2020, 05:31 AM   #5
kurbeco
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Default Re: Abit KR7A

Quote:
Originally Posted by ChaosLegionnaire View Post
ah yes, i did not notice the two caps near the cpu socket by the main atx connector. those are tricky. i dont wanna ass-u-me anything lest things blow up and damage the board.

do u have a multimeter? if so, check for continuity on the positive leg of the 2 caps by the main atx connector with the 3 caps by the cpu vrm mosfets. if its a short, it means they are all part of the cpu vrm out filtering circuit, so its fine to use 2.5v caps there because the cpu vcore voltage of the athlon xp cpu is only 1.6v. even overvolted, the voltage wont be more than 1.7-1.8v so its still fine.
I have checked, and there is continuity between the positive leg on those caps.

I do intend to run a 1.4GHz Athlon T-Bird in this board, it has a slightly higher default vcore of 1.75v, and in the past I ran this model of board with a modification to the voltage regulator to let me take that over 2v. To give me the headroom to do that, I think using higher rated caps would be safer

I'm struggling to find any 2700uF that are > 2.5v though - so maybe I just don't modify the board further for high vcore.. or would 1500uF and 4v be acceptable;

https://uk.farnell.com/panasonic/2se...-20/dp/2354614

Though they are SMD, and the 2.5v caps I can find are through-hole.

https://uk.farnell.com/panasonic/4sv...ial/dp/2354754

or https://www.digikey.co.uk/product-de...198-ND/3998084 - 2200F -6.3v

For the output caps, do these look suitable; https://lcsc.com/product-detail/Soli...M_C178378.html


I may then leave the teapos for now, and see how the system functions - if I notice issues I'll whip out the desoldering gun again
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Old 02-17-2020, 07:21 PM   #6
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Default Re: Abit KR7A

i have heard someone say that u shouldnt run polymers too close to their voltage limit or else the leakage current will be too high and the vrm wont like it. however, 1500F is too low when the original is 3300F because this could affect the overclock since u said u wanna overclock. there is one case here of decreasing the capacitance affecting the overclock. otherwise, normally for running at stock, halving the capacitance for polymodding wont have any issues for a high switching frequency vrm.

but fortunately, i think there is one series that can save u. u can try chemicon npcap psg series 2200F 16v 10x20mm. since its 16v, u dont have to worry about frying both the cpu and caps anymore, just the cpu lol! however, im not sure of its availability in the uk. also cost could be a factor since its rated as a 15k-20k hour cap! definitely long lasting and able to stand up to whatever abuse u throw at it but your wallet will have to pay the price for it... good things are never cheap.
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Old 02-18-2020, 06:22 AM   #7
kurbeco
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Default Re: Abit KR7A

OK, so to replace the 5 output caps (3 closest the CPU and 2 the ATX power connector) which are currentl Nichicon - 3300uF 6.3v 105c x 5 (10mm dia 25mm high approx) HM(M), I will use

https://www.digikey.co.uk/product-de...315-ND/5824538

Given they're 16V, I guess I can use them for the two input caps as well?
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Old 02-18-2020, 03:12 PM   #8
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Default Re: Abit KR7A

for the input, i'd use panasonic fr 4700F 6.3v 12.5x25mm caps. they are 10k hour rated electrolytic caps and should also last u a long time. esr is slightly less important on the input. i'd try to keep the capacitance the same instead.

even tho the rubycon zl caps currently on the board are 5k hour rated caps, the datecodes on them show that they were made in the year 2000! so they are over 20 years old! so its time for a replacement and an upgrade with better and longer lasting ones.
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Old 02-18-2020, 03:53 PM   #9
kurbeco
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Default Re: Abit KR7A

Thank you so much for all your help.

I've got some of the Rubycon ZL caps (new from https://uk.farnell.com/rubycon/6-3zl...-20/dp/1144675) so I'll fit those instead, and have actually found the ChemiCon caps a little cheaper at https://www.mouser.co.uk/ProductDeta...XRVD5aZg%3D%3D which is odd, as as far as I know they're the same company - but oh well

I'll get them ordered, and once fitted - I'll update this thread on how it all went
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