:confused:Capacitor Advice:confused:

[Memphis_Raines]

Hello All

I got a bit of a problem with a motherboard that I am working on. I don't know enough about electronics to carry on but I want to learn, and this looks like a great place to start off

Anyway to my problem. I am trying to repair an Intel Bayfield motherboard and 5 of the capacitors are shot. They are 6.3v 820:mu: capacitors made by what looks like Michicon if thats any help. I've google'd it and all I come up with are links to Rubicon and they say its a discontinued part

I have a few hundered 1000:mu: capacitors I can use off of other older boards but I dont exactely know what :mu: means and am afraid of blowing something after reassembly. My reasoning is if its bigger something bad will happen LOL. Being an IT Technitian they dont exactly teach you the cool stuff.

Thanks a lot for any help in advance.

 

[dknguyen]

u means micro. Similar to k = kilo, m = milli. So 1000u means 1000uF, Farads being the unit capacitance is measured in. 1000x10^-6 Farads is how big those capacitors are. The 10^-6 is due to the u.

If they are bypass capacitors you should be able to replace them as long as the value isn't too far off. If the caps do something else other than bypassing it could be a problem. THey're probably for bypassing if they are that big.

Do you know what "recapping" is? If you don't (or if you do but don't know anything about it), Google it. Apparently a lot of people go through speakers and stuff replacing capacitors.

 

[Memphis_Raines]

Hey dknguyen

Thanks for the advice. By bypass what do you mean tho. I have heard of using capacitors to "filter" power, is that what you mean. As I said in my previous post I can go from 820 "microfarads" to 1000. In "Farads" would that be a substancial amount.

I have indeed heard of recapping and have done it before but with the same capacitor values, abeit by taking a sample to the electronics store But seeing as it is the holiday season and they closed I can't even ask if they have some lying around. Considering that the size I am looking for is discontinued by the manufacturers the likelyhood of me finding those would be slim anyways.

"edit" I just got off the phone with a guy I know who works with electronics. He says the voltage doesnt matter but the capacitance does. He says a higher voltage wont matter. Is that right?

 

[fingaz]

Strictly speaking he is correct. . . it is always fine to substitute a higher voltage. But we also find that in some circuits it is also fine to substitute capacitors with the next nearest capacitance. . . Though I'm not sure whether it's ok to substitute in your circuit. . .
The difference between the two (820uF and 1000uF) may or may not be substantial, it all depends on the nature of the circuit.

If I were you, I'd just wait until you can get to an electronics shop for the correct parts.

BTW there's a guy on ebay selling them, here's the link
http://search.stores.ebay.co.uk/Sur...3QQfsubZ2159061QQftsZ2QQsaselZ4733697QQsofpZ0

 

[Memphis_Raines]

Hey fingaz

Thanks for the link. Very helpful.

The caps that need to be replaced are the caps that control the vcore voltage on the cpu. There are three there that "burst" and then the other two are to control the voltage on the ram slots (they also blew). The reason they blew was because the server they had this board in was sitting in a roof with an ambient temperature of about 40 degrees centigrade! The processor was running at about 60 degrees before I got to it so I can only imagine how hot the little guys were running. The server has only been running a year.

I any event yeah I am going to wait till the second when most stores open and get some. Thanks very much for the help you guys.

 

[Top Cap]

For a few cents more you can buy higher temperature ones that might help if the board is going back to that oven! Funny that they all burst, either a poor component from Taiwan or maybe over stressed by excess voltage. In the latter case you may have to change a few chips!

 

[Nigel Goodwin]

For a few cents more you can buy higher temperature ones that might help if the board is going back to that oven! Funny that they all burst, either a poor component from Taiwan or maybe over stressed by excess voltage. In the latter case you may have to change a few chips!

It's not 'funny' at all, it's a well known problem caused by faulty electrolyte across a HUGE range of capacitors - it even made the TV news a few years ago.

Essentially an engineer for a company who make electrolyte left and went to a rival - he took with him (stole?) the formula for their new electrolyte, and his new company put it into production, and sold it to capacitor manufacturers. Meanwhile, the original company were still developing the product, and the stolen formula was for a known inferior product, not suitable for release. The faulty electrolyte was used in millions of capacitors by many different manufacturers (because it was offered cheaper, as there were no development costs to pay for!) - many of these founf their way intp motherboards.

I recently repaired my old motherboard at work, it used to crash a lot - so I bought a new P4, and mended the old board later.

BTW, a 1000uF is perfectly fine to replace an 820uF (check tolerence specs on electrolytics!), and higher voltage is fine (probably better) - but you should definately use 105 degree capacitors (I keep nothing else at work now).

 

[Memphis_Raines]

Hey Top Cap

Yeah well we have replaced the board already with a new unit so im not too woried about it for another year but i would like to get the Bayfield running nice for myself. The board worked it was just too unstable (for a server at least). We have uprated the cooling and ventilation in the server cage so its a lot better now. 30 degrees ambient and 55 degees for the cpu. We installed a Gigabyte cooler, i cant remember its name. Basically a high pressure 80mm fan ontop of a pre lapped copper pipe heatsink, so that should help. But I am not too worried since they are installing a new server on that site in about 10 months.

Hey Nigel

Thanks for that. If thats the case I got some brand new Rubycon 6.3v 1000mF's left over from my graphics card. At home at the mo so I'll try in the morning and let you guys know how it works out

 

[dknguyen]

Did anyone tell you what bypassing is yet? I didn't see it so I will now. BYpassing is when you place the capacitor across the main power rails near to whatever is getting the power. It acts as a "mini-battery", if you will, to respond to fast changes in power demand which the main source cannot respond fast enough to. It helps smooth the input voltage too. As you can see, for something like that the exact value of the capacitor isn't overly critical as long as its within a particular range- not like a filter or something where the cap will change the the way it works.

 

[ElectronikCid122]

they should work as long as the voltage isnt lower than the shot ones on there now

 

[Aidan.Hedley]

No one has posted about ESR and ripple current yet, you need to check the specification for the originals using a data-sheet and make sure your replacements are better than or as good.

ESR effective series resistance this is a measure of capacitor quality, ripple current is linked, generally low esr = higher ripple current = higher quality + higher price if you use capacitors with too low a rating they will have a short life or your circuit won't perform as expected.