Replacing OST caps on Microstar KT6 Delta motherboard

[c_hegge]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

As far as appropriate replacements are concerned, The panny FMs you posted in your first link would actually work. The ESR is very slightly higher, but they would be close enough.

Polies like these (http://au.rs-online.com/web/p/alumin...itors/7955673/) would have a theoretically longer lifespan, but they are expensive and, on an older board, the lifespan might not matter than much as either would outlast the rest of the board.

BTW, If you can't revive this board, I'm pretty sure I have a working MSI KT6 Delta just like it which you could have for the cost of shipping.

[socketa]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Whoops!
Sorry, that wasn't the link i meant to post. (that's what i get for having 3 browsers, and 30 tabs, open)
At rs-online, i couldn't find any matching aluminium electrolytic replacements for original 6.3v 2200uf 2500mArms caps

The link i was intending to post was this:
http://www.digikey.com.au/product-se...=0&pageSize=25

Anyway, mariushm explained, and i now understand why.
Can we please return to post #7

[Agent24]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

And note that rs-online don't readily supply the motherboard caps to plebs (unless you want 600 of them)
Is this some kind of a conspiracy?

Really? The link you showed had Minimum Order Quantity (MOQ) of only 5. I buy capacitors from RS NZ a lot and most are MOQ 5 or 10. If it's something like 600 you are probably trying to buy a whole box\reel\etc.

[socketa]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Thanks again,
Nicely explained

Yes, i noticed polymer ripple ratings were a lot higher.
I just had a look at the bios and saw VCore is 1.55v

I thought that capacitance was an important factor, because i read that the capacitor is placed between +ve and -ve rails to smooth the rectified current.
Using the analogy of the balloon teed into a water pipe, that that is turned off and on at regular intervals - If the capacitor's capacitance is not high enough, then it will not store enough charge to supply the same current (compared to the the 2200uf capacitors) when the rectified wave is in the vicinity of a trough.

Can you, or someone else, briefly explain how a lower ESR justifies using a significantly lower capacitance replacement. (say, from 2200uf to 1200uf)
i.e. where do you draw the line - why not 600uf?

I'm educatedly guessing that a lower ESR (for a capacitor) means that the charge that is held by the capacitor faces less restriction by the capacitor as it is being released?
So therefore, for the 2200uf capacitor to be replaced by one of a lower capacitance (and lower ESR), it must have had some redundancy (not coming close being completely discharged during each cycle)

If that is the case, then i now understand why.
Amen Ra?

Also, would it be a better choice to use a polymer as a replacement for these capacitors (reliability, lifespan etc)

[mariushm]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Polymer capacitors are harder to produce at such high capacitance values.

Also, motherboards don't actually need that much capacitance to work, but motherboard designers use such large capacitors (and often several of them in parallel) because the bigger capacitors have lower ESR and can handle higher currents. Paralelling several capacitors further reduces the ripple.
Polymer capacitors have much lower ESR from the start and they can handle higher current ripples so it's quite normal to see polymer capacitors of lower capacitance used.

For example, while you may have 2200uF 6.3v capacitors now near the CPU, these can be replaced with.. let's say 1500uF 2.5v polymers, or 1200uF 4v... because the CPU uses less than 2 volts when running. The manufacturer used 6.3v electrolytics because that's the lowest common voltage rating for electrolytic capacitors, not necessarily because it was required by the circuit.

[socketa]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Thanks
So, after reading that, i thought that polymer caps are the way to go now.

I just checked out nichicon's range of conductive polymer aluminium solid electrolytic capacitors and found none that were suitable to replace my 2200uf's.
Nearly all of them were well below this capacitance value.
Why is that?

Is it because there is no demand for these capacitors now, or do the new motherboards use low value capacitors now? (i thought that they would require higher value caps, judging by how fast the modern processors are working)

So basically these discontinued caps are the only option for older motherboards now?

[mariushm]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Manufacturers reduced the volume of ultra low esr electrolytic capacitors production or even discontinued series, because most motherboards nowadays use polymer capacitors for the critical sections (if not for everything).
For example, Nichicon has discontinued their HZ, HM and HN series capacitors...

A lot of customers also tend to be more informed or eat up the marketing that says "all solid capacitors" so they look after that.

Therefore, it's possible distributors like RS-Online may not want to risk stocking such capacitors (they have to order minimum quantities, for example 5000pcs) when there's a high chance it's going to take a long time to sell them.

[socketa]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Thanks for clearing that bit up.
Reading through the forum, i see that that is a very important spec.
Have learned a bit about capacitors in the last few days.
I was looking on Ebay and they all look extremely suspect.
And note that rs-online don't readily supply the motherboard caps to plebs (unless you want 600 of them)
Is this some kind of a conspiracy?

Also have noticed, on the various datasheets, that ESR value is close to Impedence value.
For practical purposes, are they the same?

[Topcat]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

There is another number written on the caps : 0338 - what is this? (is it 0.0338 impedance?)

No, that's the datecode. The cap was made the 38th week of 2003.

Here's a good replacement for those:
https://www.badcaps.net/store/produc...roducts_id=137

I do ship to Australia.

[socketa]

Hi Peeps,

Trying to resuscitate a half-dead motherboard (not booting or beeping, power switch works and CPU fan spins , but thankfully not destroying CPUs or RAM)
A couple of the caps are slightly non-flat, and i have read they they are prone to fail.
There is 7 of these on the motherboard, and they are all the same specs

Here is the Original capacitor specs
Brand :OST
Series : RLX
Capacitance : 2200uf
Voltage: 6.3v
MAX Op Temp : 105 deg Celsius
Dimensions 10mm X 20mm
There is another number written on the caps : 0338 - what is this? (is it 0.0338 impedance?)

I looked up the datasheet for the OST RLX series and they state that ripple is 2500 mArms and impedance is 0.015, for this particular capacitor.

The best that i can find is here:

http://au.rs-online.com/web/p/alumin...itors/5260982/
It is a panasonic, that closely matches the original
(the OST capacitor's impedance of 0.015 is out of the range of this panasonic's, which is 0.018 - 0.054
I'm picking that a lower impedance is not ok?

Also have read that it is best to get a cap with the same, or higher, ripple current rating that the original.
This panasonic is the one with the highest ripple current rating (2470mArms) - just short of the original 2500mArms

Have i chosen the best one from au.rs-online.com,
or should i look for a one with a higher ripple current rating, higher impedance (and a bit higher capacitance, because there is no 2200uf's that are suitable)?

Thanks