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Motherboard capacitors.

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First post, by Baoran

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Is it ok to replace a 22µF 25V capacitor on a motherboard with a 22 µF 16V capacitor? My first thought was that there are no such high voltages on a motherboard, but I wanted to make sure and my only other option would be to use a 50V capacitor which feels bit excessive.

I have not recapped a motherboard before, but I just recently got a super socket 7 motherboard just for few euros, but it has couple bulging caps so I thought that there is nothing to lose trying to fix it.

Reply 1 of 24, by Vipersan

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When replacing any capacitor the general rule is to use the same capacitance value of slightly higher ..
and as for voltage the same ie the same or higher..
never go lower with either ..
so for example 820uf 16v could be replaced with 1000uf 25v .....not the other way round.
hope this helps

Reply 2 of 24, by Strahssis

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Vipersan wrote:
When replacing any capacitor the general rule is to use the same capacitance value of slightly higher .. and as for voltage the […]
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When replacing any capacitor the general rule is to use the same capacitance value of slightly higher ..
and as for voltage the same ie the same or higher..
never go lower with either ..
so for example 820uf 16v could be replaced with 1000uf 25v .....not the other way round.
hope this helps

That's completely true and besides the 50V capacitors are not a whole lot more expensive, so I'd definitely go for those in your situation. 😀

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Reply 3 of 24, by root42

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Are you talking about electrolytics or also tantalum? The latter should always be overprovisioned by at least 50%, since they are finnicky when put on overvoltage. They may fail catastrophically then...

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Reply 4 of 24, by Baoran

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I was thinking of replacing with the same type of electrolytic capacitors because I don't know enough about capacitors to know what kind of different type of capacitors would work. There are also 1000µF 6.3V capacitors next to the cpu socket that are bad and I was thinking of replacing those with 1000µF 16V capacitors.

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Reply 5 of 24, by Vipersan

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Baoran wrote:

I was thinking of replacing with the same type of electrolytic capacitors because I don't know enough about capacitors to know what kind of different type of capacitors would work. There are also 1000µF 6.3V capacitors next to the cpu socket that are bad and I was thinking of replacing those with 1000µF 16V capacitors.

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Excellent idea to go _up Voltage_ imo ..
providing you have the physical space/footprint.
Luckilly modern caps of the same or higher capacitance and voltage have a smaller profile than older caps ..so you can generally do exactly this..

As a general rule I always up voltage on replacents ..replacing 6.3 v with 10 v ....10v with 16v ...16v with 25v ..etc

..and when replacing electrolytic caps in psus ..always use LOW ESR 105 degrees if possible..

Last edited by Vipersan on 2018-11-06, 17:25. Edited 1 time in total.

Reply 6 of 24, by Baoran

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If the motherboard works, it seems pretty decent. It seems to have 1Mb of 5ns cache on board. I was especially worried about those capacitors next to the cpu socket because I don't want it to fry the cpu, so I have not even tried to power it on and I won't at least until I try to see if I can replace the capacitors that are bulging.

Reply 7 of 24, by Vipersan

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Baoran wrote:

If the motherboard works, it seems pretty decent. It seems to have 1Mb of 5ns cache on board. I was especially worried about those capacitors next to the cpu socket because I don't want it to fry the cpu, so I have not even tried to power it on and I won't at least until I try to see if I can replace the capacitors that are bulging.

Very wise ...

Reply 8 of 24, by Baoran

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Someone who I just talked to told me that those capacitors next to the cpu socket have to be 6.3V and you can't use higher voltage ones there because it changes something. Now I am confused.

Reply 9 of 24, by Vipersan

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My answer would be ...no I dont agree.
Smoothing or decoupling capacitors aren't so critical ..and a higher voltage rating just means they are stressed less.
There _are_ situtaions where the UF capacitance value is critical ..but not for decoupling ..
Up voltage and up capacitance is preferable ..but not by silly amounts ..
you wouldn't for example use 1000uf in place of 10uf
The next voltage rating up ..and a few microfarad higher wont cause problems....doing this job
trust me..

Reply 10 of 24, by elod

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Vipersan wrote:
My answer would be ...no I dont agree. Smoothing or decoupling capacitors aren't so critical ..and a higher voltage rating just […]
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My answer would be ...no I dont agree.
Smoothing or decoupling capacitors aren't so critical ..and a higher voltage rating just means they are stressed less.
There _are_ situtaions where the UF capacitance value is critical ..but not for decoupling ..
Up voltage and up capacitance is preferable ..but not by silly amounts ..
you wouldn't for example use 1000uf in place of 10uf
The next voltage rating up ..and a few microfarad higher wont cause problems....doing this job
trust me..

You can go higher with capacity. No reason to up the voltage. Get some decent caps though. When specs are available match (in power supplies) or exceed ESR and ripple ratings.

Reply 11 of 24, by gdjacobs

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Don't stray too far from the ESR rating unless you know that part of the circuit isn't used for feedback.

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Reply 12 of 24, by root42

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Two of those caps look extremely bulging. Also yes to the fact to go with the samw or similar ESR rating.

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Reply 13 of 24, by Baoran

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How do I find out ESR rating for both the ones that are currently on the motherboard and the replacement capacitors I am about to buy?
Basically I am asking how do I actually choose the replacement capacitors.

Reply 14 of 24, by TheMobRules

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Just get some good (Japanese) low ESR 1000uf 6.3V or 1000uf 10V and call it a day, those are extremely common values in Socket 7/Super 7 motherboards. No need to worry about different voltage or capacitance, it won't be of any advantage unless you're trying to fit them in cramped spaces where the usual sizes may be too large. Be sure to replace all of those, if a couple are bulging I'd say the other ones near them are probably also about to croak.

Using caps with too low ESR *may* be a problem but in my experience those S7 motherboards are pretty tolerant in that sense.

If you also want to replace the smaller ones just go for same capacitance and same (or higher) voltage and make sure they are of a Japanese brand and rated up to 105C.

Reply 15 of 24, by gdjacobs

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Baoran wrote:

How do I find out ESR rating for both the ones that are currently on the motherboard and the replacement capacitors I am about to buy?
Basically I am asking how do I actually choose the replacement capacitors.

Identify the capacitors (manufacturer, series, voltage, case size).
Find the datasheet and look them up.

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Reply 16 of 24, by Baoran

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http://www.samwha.com/electric/product/list_pdf2/RD.pdf
Would these as 16V and 1000 µF work to replace those 6.3V and 1000µF ones? That datasheet doesn't say anything about ESR either though really.

Reply 17 of 24, by gdjacobs

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ESR is given as dissipation factor in that datasheet.
https://www.illinoiscapacitor.com/pdf/Papers/ … _factor_ESR.pdf

Unfortunately, they don't specify the valid tan delta frequency range, but hopefully you'll be pretty close to a comparable ESR if you calculate for 100 khz.

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Reply 19 of 24, by gdjacobs

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You'll have to identify the old caps, ESR appears to be about 100 mOhms at 100 khz for the Samwha caps which is pretty middling. It might be enough for this application.

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