Introduction: How to Repair Capacitors on Computer Motherboards and Other Electronic Devices.

Picture of How to Repair Capacitors on Computer Motherboards and Other Electronic Devices.

This instructable will show you how to diagnose and repair bad capacitors on computer circuitry saving you money on new appliances and preventing landfills from filling up. 

Always unplug electronic devices before opening them!  Even after opening make shore you discharge all the capacitors with a discharge rod.

Step 1: Materials

Picture of Materials

You will need.

a Soldering iron
a cutting pliers
safety glasses
rosin core solder
the replacement capacitors
an anti static band (if your working with delicate circuitry)
a de soldering pump (optional)
and de soldering wick (optional)

Step 2: Diagnosing the Bad Capacitor(s).

Picture of Diagnosing the Bad Capacitor(s).

You should be looking for capacitors that are bulging slightly at the top or bottom, have black, brown or white goo oozing from the top, or that are pushing themselves away from the board.

Step 3: Removeing the Capacitors

Picture of Removeing the Capacitors

  Desolder the bad capacitor(s) from the board. Don't immediately throw the bad capacitors away, we'll need them for the next step.  Also not the direction of the gray colored band on the side of the capacitor. The new capacitor must be inserted the same way.  Wear eye protection sometimes the bad capacitors can explode because there under pressure.

Step 4: Adding the New Capacitors

Picture of Adding the New Capacitors

The bad capacitor(s) should have markings on the side like for instance 10v 100µf.  replace the capacitor(s) With ones with the same markings.  You can use a capacitor with the same or higher voltage. But don't change the capacitance.

Step 5: You're Done

Picture of You're Done

The application you changed the capacitors on should work perfectly now.


knahrvorn (author)2017-11-06

Thanks for the instructable. Is there any need/recommendation to also change ceramic capacitors (or other components)?

ShadrachH (author)2016-11-13

I am delighted to know this site exits, please keep this job up. However the circuit on which the capacitors are to be changed should fully be dead or completely be discharged before replacement or repairs take place on it.

tunnut (author)2016-01-06

filing luckly (author)2015-02-26


iglierseke1 (author)2015-02-09

Can I replace a 1000uf 6.3v for a 1000uf 10v cap? please help me ///

ivan.s. (author)2015-02-05

many times I have done these replacements. After changing bad capacitors with a new ones all works great. If you would like to see how I done this follow my blog

JR (author)2012-05-03

I purchased a used benchtop power supply. As soon as I plugged it in at least one capacitor popped. I am trying to evaluate whether I can repair the device by replacing the capacitor or if I will need to perform a more in depth repair. When a capacitor pops, what is the likelyhood of other components being damaged? What type of components would be most sensitive to the failure? What happens electrically as a capacitor fails? Is it equivalent to a short or an open?

coolpizzadude (author)JR2012-05-05

Capacitors are cheap. I would replace it and see what happens. Capacitors filter out ripples in the curent or noise. They basically act sort of like mini surge protectors. You may or may not have damaged somthing else when it blew.

msuzuki777 (author)2010-09-14

Great Instructable!

Many years ago I did some research on these capacitors. It turns out some companies had stolen some designs from a Japanese manufacturer and left out some of the chemical formula. So millions of these were put into products.

Safety: All though not a major concern, motherboards can be subject to static electricity damage. So try to ground yourself to earth ground especially when working on carpet. In the U.S. all those screws in between the AC sockets are tied to earth ground.

The author is correct that polarity is very important. The little grey stripes indicate the negative side. And higher voltage ratings doesn't matter. The voltage rating is just the maximum voltage that can be applied to the component.

And the author is also correct that shape and size don't matter as long as you can get it to fit and soldered.

ashiekh (author)msuzuki7772012-02-04

"Many years ago I did some research on these capacitors. It turns out some companies had stolen some designs from a Japanese manufacturer and left out some of the chemical formula. So millions of these were put into products."

I've read this also, but it does not make sense.

Would an established capacitor maker, with their own magic brew just take another formula without testing? It just does not make sense.

msuzuki777 (author)ashiekh2012-02-04

My memory isn't the greatest but I believe these were foreign start up companies that were not established capacitor makers. Since they probably didn't have a design engineering staff, they could sell it cheaper then reputable companies.
Purchasers for the motherboards, printers, etc., looked for the best price. They may have done some internal testing but, in this case, the major failures were often years down the road. I worked in the electronic reliability testing for many years and know the difficulties of finding long term failures in a short period of time. (Manufacturers can't test a product for 10-15 years before they sell it as it would be obsolete)

As a retiree, I buy a lot of my electronics on ebay, mostly from China. Most of it has been fairly good quality but I have had some bad, especially cables, audio and USB. But when I spend a $1 or $2 for a cable, I don't expect a lot.
As for long term reliability, I have even less expectations, but then I am old.


ashiekh (author)msuzuki7772012-02-04

That makes a lot of sense, but I believe even well established companies suffered failures.

There is also accelerated aging (at high temperatures) to try and gauge future failures.

msuzuki777 (author)ashiekh2012-02-04

You are right, well established companies suffer failures also. And there's various levels of well-established as far as quality and reliability are concerned.
You are probably more familiar with the current state of electronic manufacturing but I suspect that 99% of electronics is manufactured overseas. Though much is probably outsourced by established companies, there is still issues of transfer of technology and quality control.
My experience was in testing products rather than components. Heat was the primary gauge but we also used cold, high/low humidity and vibration in all axis. Another method we uses was reliability software where you input a bill of materials and estimated weakest components based on reliability data from the component manufacturers (primarily MTBF).
In my experience, I almost never see an electronic component failure unless it was subject to static or lightning. Most of the failures I've seen are mechanical, especially fans and connectors.


ashiekh (author)msuzuki7772012-02-04

I feel certain that you know much more than myself, but I wonder if the slew of capacitor failures was not perhaps due to the higher power CPUs, and that perhaps design and solid state capacitors has finally caught up. The future trend seems like it might be headed in the opposite direction, toward lower consumption.

Given that computers are said to consume more energy than air travel, this might not be a bad thing at all.

msuzuki777 (author)ashiekh2012-02-04

In electrical terms, power is voltage times current. But if you've been following CPUs in computers, they used to be 5Vdc, dropped to 3.3Vdc and I believe some of the newer ones are 1.8Vdc. So higher power means higher current.

These capacitors are electrolytic capacitors used to filter DC power. Current doesn't actually pass through them. That is why they only have a voltage rating and a value. So in a higher powered circuit an electrolytic capacitor may not filter as well but it wouldn't contribute to a higher capacitor failure rate.

There is a trend to low power consumption. IMHO, this is due to lower CPU voltages and multiple cores. Multiple cores generally run at lower speeds (less power) but higher performance (because of multi-cores and other design advancements.

By the way, I just ran across an interesting but somewhat biased website:


ashiekh (author)msuzuki7772012-02-04

But current passes into and out of them, and they have a voltage rating, a capacitance AND an effective series resistance (ESR), and when this is high, they run hot.

So I must differ with you on this, the higher the power of the circuit, the higher the heating of the capacitor and so the faster it fails.

msuzuki777 (author)ashiekh2012-02-06

I, respectfully disagree. Electrolytic capacitors in digital computers are used to filter power supplies. Just about the only current that passes through them is when the computer is turned on and the capacitor charges up to the power supply voltage. An electrolytic capacitor in a digital circuit should never get hot or even warm, no matter how high power the CPU. The only reasons I know of an electrolytic getting hot is if they are installed incorrectly (polarity) or if they are defective.

Now I agree that electrolytic capacitors in an analog circuit can pass current. And this is important especially in AC motor circuits.

So I would like to see any digital computer circuitry that has electrolytic capacitors that pass much current and heat up.


ashiekh (author)msuzuki7772012-02-06

Then why do they take care to use capacitors with low ESR, sometimes even less than 0.01 ohm. They pass a lot of current trying to keep the voltage constant for chips that are very variable in their current consumption.

msuzuki777 (author)ashiekh2012-02-07

Out of curiosity, I had to do some more research on this.
First, I was wrong about electrolytic capacitors not heating up in operation. They do.
"Ripple current is the rms value of alternating current flowing through a capacitor." This means it's AC current not DC so higher steady currents don't affect it.
Second, I believe ripple current is more of an effect of input variations than output. But output AC loading will affect it. Higher powered systems are usually running at higher frequencies which could increase ripple current so you may be right about them generating more heat. Another factor is higher powered CPUs generate more heat which will likely raise the ambient temperature of the motherboard which will also raise the temperature of the capacitors.
Third, I think the main reason designers use capacitors with lower ESR is that lower ESRs improve their filtering capabilities.
Full disclosure: I am speaking more in practical terms (technician) than in theoretical terms (engineer) as I do not have an engineering degree.

So have you seen/heard of more capacitor failures in higher powered systems? Personally, speaking, I haven't seen any electrolytic capacitor failures except when I put one in backwards. In my opinion, if a motherboard is properly designed, you should see minimal failures of all components including capacitors. The only significant motherboard capacitors failures I've heard of, seem to be because of the 'bad' caps.


ashiekh (author)msuzuki7772012-02-07

Absolutely, AC current; the power supply capacitors take care of the input ripple and the mother board capacitors of the output ripple. The lower ESR will mean reduced resistive heating in the capacitor.

In is my theory that the slew of failures was not so much due to industrial espionage as the increasing demands of high power CPUs and that designs then caught up with this by using the new solid-state capacitor technology.

All this said after the need to recap the mother-board of a G5 iMac a couple of weeks back. I used electrolytic capacitors, and now wonder if perhaps I should have moved to solid-state types.

Perhaps there was a bad run years back, but for me it doesn't make sense; the well established manufacturers would surely not have use an untested stolen recipe when they had their own. Hence the theory of higher power CPUs as resistive heating goes like I^2, so just doubling the speed of a chip would increase heating by a factor of 4.

I recapped the power supplies on these machines a few years back, but one of the capacitors was not low ESR, and this failed after only 2 years; so I think low ESR is important for life.

msuzuki777 (author)ashiekh2012-02-07

I found an article that summarizes the extent of the 'bad' capacitor failures:

Your concepts may certainly have contributed to capacitor failures but how would you explain:
1 Flawed capacitors first appeared in 1996, long before high powered computers.
2. Failures in compact fluorescent lamp ballasts, LCD monitors

Here is another quote from
"In the early 2000s, Nichicon is known to have produced and sold bad capacitors to major computer manufacturers, including Dell, Hewlett-Packard, and Apple. Nichicon's capacitors were prone to pop and leak fluid, causing computer failure."

I am very aware that you can't believe everything that appears on the internet but I do believe these.

Anyway, you may have an opportunity to test your theory, if your G5 iMac fails again with the replaced capacitors.
By the way, I agree that low ESR capacitors are important in power supplies. You should also check the maximum operating temperature of the capacitors as many power supplies run pretty hot. Several articles said that power supply capacitors may get 10-15 degrees Celsius hotter than ambient.


ashiekh (author)msuzuki7772012-02-08

All very good points, and hopefully the repaired machines now last a long time.

coolpizzadude (author)msuzuki7772012-02-04

From what I have seen so far most of the devices are not plugged in to a surge protector so the capacitors take alot of the abuse. I think this is one of the primary reasons why they fail.

msuzuki777 (author)coolpizzadude2012-02-04

Surge protectors reduces voltage surges on the AC power going to the computer power supply. It is most likely that any surge problems would damage the power supply before it could harm the motherboard capacitors.

Most motherboards are powered by 5Vdc and 12Vdc which should be well buffered by the power supply. In my opinion, if capacitors on the motherboard were damaged by power surge problem, then the power supply would be completely fried.


ashiekh (author)msuzuki7772012-02-04

I agree... with you both ;-)

* I have had some equipment last a long time, possibly because of the surge protectors

* The surge would be seen mainly on the high voltage side of the power supply

ashiekh (author)2012-02-06

OK, I got to test some used power supply capacitors with the Peak Atlas ESR-70, and for those showing no physical damage I got some varying readings, which seems to suggest aging. i.e. this doesn't tell us anything we didn't know before, that capacitors age.

By mixing new with older capacitors in a parallel bank, the newer capacitors will take more than their fair share of the load as the old capacitors have higher ESR.

ashiekh (author)2012-01-31

Just because a capacitor looks physically sound does not mean it has not failed; low capacitance or high ESR (effective series resistance), so it is a good idea to change them all at once.

coolpizzadude (author)ashiekh2012-02-01

Mabe...If your a perfectionist. I have yet to see a cap the looked good but actually wasn't.

ashiekh (author)coolpizzadude2012-02-01

The ESR (effective series resistance) can degrade before any physical damage is seen.

coolpizzadude (author)ashiekh2012-02-04

Yes just like your eye sight can degrade before you need glasses. The capacitors may be degrading on the inside before you see anything but in most cases it's not enough to stop the cur cut from working. Really it's only an unnecessary, time consuming, and expensive insurance measure on my account. If you have the time and money to replace them all go for it!

ashiekh (author)coolpizzadude2012-02-04

Seems that those that replace only those that are physically damaged see follow up failures a few months later. A lot are running in parallel, so it makes sense that if some have failed, others in the group are near failure. So I'm not sure it is at all 'unnecessary' or expensive; as the trouble to strip the computer down and repeat the process is not negligible.

I should have more detail soon when I can use an ESR meter on those capacitors I removed by looked physically sound.

coolpizzadude (author)ashiekh2012-02-04

Cool I would love to see some test results. I an currently using a computer that I did the capacitor fix on and it has been going a year and a half with no probloms. It does make sense what you saying though that they could fail shortly afterward but I haven't experienced such problems..yet. If your item is very hard to get apart I could see your logic. Most computer power supplies, motherboards, monitors, and so on are usually easy to get apart so if more do fail it's not too big of a deal.

ashiekh (author)coolpizzadude2012-02-04

I hope to pick the ESR meter up Monday, so might have some news then. My computers are rather mission critical, and I'd rather they not start playing up and have me scrambling to bring them back (happened just over a week back).

I went with the Peak Atlas ESR-70 ($130) although the Bob Parker ESR kit ($70) also looks nice.
While such meters can measure capacitors while still in circuit, they may not be very useful for parallel banks, as the good units will give rise to a low ESR reading.

One thing you might want to try is see if any are running particularly hot, which might also spell impending failure.

I also find working on a mother board somewhat risky, so would prefer to keep the number of times I work on it to a minimum.

Anyhow, glad to learn your fix is holding up for you.

panic mode (author)2011-08-05

wait a second...
those capacitors were not repaired, they were replaced... (board was repaired)


carmaster (author)2011-04-29

I remember this time I had a P4 board, the caps were uber swollen.

I needed 50uF and I had 100's
So I soldered them in series and put the leads in, lol.

The final board looked like huge electrolytic caps sticking out, so unprofessional, but it worked.

adamcpennington (author)2011-03-30

Thanx for the intractable. I saw a cap that must be blown, but have been hesitant to give it a shot. I feel more confident about try now. Time to go fix my computer.

Vinsu (author)2011-03-27

Good instructable. Perceptive pictures too.

coolpizzadude (author)Vinsu2011-03-27

Thanks :)

fegundez1 (author)2010-09-13

I have gotten sets for pc at badcaps, is there anywhere else you get yours?

coolpizzadude (author)fegundez12010-09-13

What do you mean by sets? Do you mean the replacement capacitors?

frollard (author)coolpizzadude2010-09-13

I think that's what he's referring to -- I've seen motherboard repair kits that have a bunch of generic (good range) of caps, and power transistors -- usually the first parts to go.

mdgrover (author)frollard2010-09-14

I started looking at, but after a few google searches eventually found the set I needed on ecrater (

Some other key specifications to look for in your replacement caps (other than the capacitance and voltage rating) is the Diameter, Lead Spacing and Body Height of the caps, which is usually given in millimeters (mm). Some mobo's don't have much space or vertical clearance available, so getting an exact match can be pretty important.

Once you have these physical measurements (as well as the μF and V) you'll be able to search the web more accurately for the exact parts. There are a lot of eBay stores out there selling kits too, or check out Futurlec ( for pretty cheap capacitors - they also provide all the sizing specifications.

coolpizzadude (author)mdgrover2010-09-14

I don't worry that much about these measurements personally. I can make anything fit lol.

frollard (author)coolpizzadude2010-09-14

*and* you can re-route the larger caps a few mm or cm here or there with longer leads -- thats how ben heck makes the xbox 360 laptop, by laying all the caps flat and lengthening the leads.

pfred2 (author)frollard2011-02-24

*and* the longer the lead the worse the capacitor does its job. The basic design rule is as short as possible. A few mm probably not an issue but a few cm could potentially cause problems.

frollard (author)pfred22011-02-24

This is true. particularly 'inverse to the size of the cap' -- so long as it has beefy leads on it, the larger caps aren't designed to filter any high frequency stuff, just scads of current, noise shouldn't be an issue since they are filtering noise generally.

pfred2 (author)frollard2011-02-24

Larger diameter leads do help with distance but I'm still going to keep large electrolytic caps as close to the parts of the circuit that need their current as possible. For reasons too esoteric to get into here.

frollard (author)pfred22011-02-24

Agreed 100%. When possible, stick with the ideal. When you're stuck 'design' wise, it often won't hurt.

LankyDuke (author)2010-09-13

It would be wise to mention the importance of polarity in certain caps. Most PC related capacitors have the band down one side, or a mark near one of the leads. You should take note of the alignment of any caps you take out of the PCB.

Cracknel (author)LankyDuke2010-09-13

This is really important. If you get them wrong they could explode!

About This Instructable




More by coolpizzadude:How to Repair a Cracked Speaker Cone.How to clean a RoombaHow to repair capacitors on computer motherboards and other electronic devices.
Add instructable to: