Introduction: Replace Capacitor in Computer Board

Picture of Replace Capacitor in Computer Board

in this instructable we'll replace failed capacitor in PC mainboard

the mainboard here is from friend's computer. it crashed randomly for few months and now it does not allways complete startup

this may - and in this board is - caused by failed capacitor. capacitors stabilize the power to components in the computer. when they go bad the computer gets spikes or 'flickering' voltage that makes it malfunction and damages it

Step 1: Tools

Picture of Tools

new low ESR (low internal resistance) cap

pin from message board

sharp soldering tool 30 W (more may be better but dont overkill) and soldering stuff

Step 2: Find It

Picture of Find It

most bad caps have visible damage. the last image shows ok (green) and failed (red) capacitors

Step 3: Find Replacement Cap

Picture of Find Replacement Cap

you need a cap that is

the same voltage (higher voltage will work but not as good)

the same (best) or larger (max 1.5 X) capacity

external size (not too large to stuck in other components)

low ESR (low internal resistance) - this means its fast enough to react to thin and sharp spikes of too high or too low voltage. most caps in computer mainboards are low ESR. most caps in other places are not.

there is a way to replace low ESR cap with standard electrolytic and ceramic connected in parallel. i think this hack is NOT suitable for computer

in the example we'll replace 6.3 V 1000 uF with 6.3 V 1200 uF from another dead mainboard

(the other board died with smoke after being installed without spacers between it and the wall)

Step 4: Remove Battery

Picture of Remove Battery

before you start any work with the board remove the battery

Step 5: Remove It

Picture of Remove It

see what side is the - side of the cap. you'll need it later

hold the cap and heat one of the points its soldered to. if the tool takes the point then tilt the capacitor to the correct side to pull out the entry

wait for the point to cool and do that with the other one

do so few times untill you get the capacitor out

if the tool does not take the point add a tiny amount of new solder to it

if the point is connected to a large area conductor in the board (it may be between the layers of the board too) it'll sink most of the heat. its ok just keep on heating it

dont heat the point if you feel the heat spread from it to the rest of the board or if you think you can damage something

Step 6: Clean the Holes

Picture of Clean the Holes

you took the cap out. now you need to stick in the new one and the holes are full of solder

if there is hole use the pin to make it larger so you can insert the capacitor. spin and tilt it in the hole from 2 sides of the board. dont press hard to not damage the conductive layer on the walls of the hole

if the hole is blocked try to kinda solder the pin into the hole. when it cools down remove it (its made of some metals that dont stick to solder)

Step 7: Insert the New Cap

Picture of Insert the New Cap

insert the new cap with the - in the same side as the previous one

Step 8: Solder It

Picture of Solder It

heat the point with the tool and give it a tiny amount of solder. heat it for about 2 sec more so the solder fills the hole

try to make the drop on the outside as small as possible

Step 9: Clean

Picture of Clean

when soldering some transparent material comes from the solder and remains on the board. sometimes its little conductive. if there are any conductive points nearby and it kinda connects them to the capacitor then try to break the path with a plastic card

do not damage the transparent paint that covers the board

if its just on the paint its ok - the paint is not conductive

if its only between the 2 points of the cap or the points are anyway on the same conductor in the board then its ok to leave as is

Step 10: Yay

Picture of Yay

Step 11: Test

Picture of Test

install everything in the board and let the computer run. try to do what you could not with the bad cap

touch the cap to see if it heats. cool or little warm cap is ok. more is not ok (did you install it in the correct direction ? is it compatible with the cap you replaced ? are there any other failed components in the board ?)


halamka (author)2014-11-10

A BASIC computer company needs about 4 or 5 people to start. Just draw the flow charts for each function. I think a computer statement can be stored in ram. A flow chart can be written to find parenthesis. The problem with simple BASIC computers with microprocessors is that cheaters easily take control. The cheaters form a monopoly that controls chip fabrication. A certain amount of cheating is necessary. Is Microsoft really necessary?

tomhat9 (author)2014-05-12

I have removed about 20 motherboards out of service due to bloated capacitors, luckily I've kept them around. I worked in electronics for many years, but it's not like it used to be, components have gotten pretty small. I always felt that replacing components on motherboards was more trouble than they are worth. I am going to see about repairing some of these. Thanks for sharing.

SeanOTheDed (author)2014-03-01

A word of caution. While this is helpful, some information here is wrong.

  • When selecting a replacement capacitor, you CAN use a higher Voltage without fear of hurting anything.
  • However, you should NOT use a different capacitance. This is measured in Farads and has a F symbol with the unit before the F, µF, pF... If you know exactly how it's being use in a circuit you could make an informed decision to use another/higher value. But then again, if you knew how to do that, you wouldn't be here reading this would you? ;)
  • The ESR is very important here because this is the primary cause of failure in Aluminum Electrolytic Capacitors. Basically, the higher the value, the more abuse it can take before popping.

I fix avionics for a living so you may consider this a professional opinion. But don't take my word for it:

If you believe I am wrong please feel free to reply, but provide a link to your information source so we can fact check it and all learn from it.

rbennett8 (author)2012-09-13

first off this is not a hack it is simply a repair there is a difference

and you need a power supply tester and a mother board pci test card they will tell you whats wrong with computer

zack247 (author)2010-01-26

a pentium 4, nice. im gonna do this with a socket 370 mobo. don't know what happened to it but i just have to find 10 more capacitors and i can try and hope... its a really great mobo and i wnna put a celeron into it

zack247 (author)zack2472010-02-25

can i replace a 6.3v with a 16v capacitor? or will that do damage?

app0 (author)zack2472011-01-22

It shouldn't, but you better go and find the exact one and ALWAYS BUY BRANDED CAPACITORS like Rubycon, Sanyo, Panasonic etc.

zack247 (author)app02011-01-22

thanks for letting me know.

just in case anyone wanted to know, the board did work, until the power supply i had hooked up to it literally blew out. there are no bad caps and now i dont know whats wrong with it because changing the cpu, ram, and resetting the bios dont do anything. it just keeps beeping.

app0 (author)zack2472011-01-23

Can you tell me who is the bios manufacturer and the beep pattern?

zack247 (author)app02011-01-23

i dont know the bios manufacturer, but it is a ibm pro 300_afp motherboard, and it just keeps beeping, it doesn't stop. nothing shows on the screen either.

app0 (author)zack2472011-01-23

Check what's written on a label on a BIOS chip. A photo would also be great.

zack247 (author)app02011-01-24

i'll see if i can get a photo of it. i also might have gotten the board name wrong.

app0 (author)zack2472011-01-24

Usually on "default boards" (nonames) or "ideal boards" (complies with all standards of AT/ATX) a continuous beep is a PSU/CPU problem, however it might be different. Also be sure it comes from the speaker, not from parts.

zack247 (author)app02011-01-24

here: i mistyped the model number, it should be Pro300A_AFP.
a quick google search and i found the same board as i have got.

the sticker on the bios says:
IBM (C) 2001
REV .09

thats all i could find, let me know if i need anything else.

app0 (author)zack2472011-01-24

IBM Desktop BIOS Beep Codes:

1 short Normal POST System is booting properly
2 short Initialization error - Error code is displayed
1 long, 1 short System board error
1 long, 2 short Video adapter error
1 long, 3 short EGA/VGA adapter error
3 long 3270 keyboard adapter error
Continuous Power supply error - Replace the power supply
999s Power supply error - Replace the power supply
No beep Power supply failure - Replace the power supply

Here you go

zack247 (author)app02011-01-25

really? but the power suppkies work fine on any other board, i'll try again, but do you think maybe there is a chip burnt out on the board thats telling the motherboard the wrong thing?

app0 (author)zack2472011-01-24

Oh noez the Instructables comment script cuts out the TAB's

zack247 (author)app02011-01-24

well it cant be a cpu problem, i tried multiple cpus and got the same problem, same with PSU's.

It is definitely coming from the speaker on-board, i am still not sure whats wrong with it yet, i am going to see if i got the model right, i might have mistyped it.

gurtek (author)2009-06-13

nice and useful............

bwpatton1 (author)2009-02-23

is this from a dell optiplex? Gx 260 possibly

bwpatton1 (author)bwpatton12009-02-23

Hey, Itz an Energy Star you can get a tax deduction for that i think.....

11010010110 (author)bwpatton12009-02-23

shutting down the computer / monitor when not in use (instead of standby etc) can save way more energy than energy star compliance using minimal hardware (like onboad video card and not agp / pcie one) saves some energy too i am not from the us. as far as i know energy star gives tax refund only in the us

11010010110 (author)bwpatton12009-02-23

nope its gigabyte GA-8IG1000MK in a locally assembled pc without company name

bwpatton1 (author)110100101102009-02-23

oh, cuz the optiplex had problems with capacitors on the MOBO

11010010110 (author)bwpatton12009-02-23

i have a second hand 2001 GX150 pentium 3 and its capacitors are ok. no experience with newer dells replacing capacitors is done the same way in all computers

navarrofeds (author)2009-01-25

good Instructable ! I have a computer that will not pass post and I think its the mobo possibly a fried cap. I am waiting on a vid card to try that and have tried everything else. just wanted to say thanks this might com in handy

NachoMahma (author)2008-12-30

. Good job. . Do you really have to remove the flux (step 9)? It was never a problem for me (but the last mobo I touched with a soldering iron had an 8088 processor running at 4.77MHz).

11010010110 (author)NachoMahma2008-12-31

there is conductive flux. i discovered it by accident i was working on an audio project and could not figure why the opamps are stuck in saturation. flux between 2 ajacent entries of the opamp (vcc and + in) had a resistance of ~ 6 K ohm. more than enough to make trouble. i scratched it away and it worked it can be left as is if its just across the capacitor (it may take some leak current but if its only vcc and earth the computer won't mind). i'd still remove it if there is no risk to damage the board in the process

NachoMahma (author)110100101102009-01-02

. Good to know. I'll keep that in mind if I ever do any more soldering.

philipster (author)2008-11-13

good but too many cautions u have to take into account theres resisters that can be affected by the hear of soldering iron

11010010110 (author)philipster2008-11-13

thats why you should be cautious when you feel the heat spread over the board

mikecraghead (author)2008-11-10

I presided over a school computer lab with a "bad batch" of Dells that had bad caps...
I found this site helpful:

AndyGadget (author)2008-11-09

There was a lot of faulty capacitors used in computers and many other types of equipment a few years ago. These would fail after a couple of years of use. My company had a large batch of IBM PCs which all died sooner or later with bulging mobo caps. (Wiki info HERE )
Random lockups are the most common symptom as the internal resistance falls and the ripple on the power lines increases.

About This Instructable




Bio: msn messen_er : aketch_m _
More by 11010010110:view images as guestsafely pack steel railsplastic bottle pole
Add instructable to: