Replace Capacitor in Computer Board

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Introduction: 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

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

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

Step 3: 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

before you start any work with the board remove the battery

Step 5: 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

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

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

Step 8: 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

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

Step 11: 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 ?)

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    user

    We have a be nice policy.
    Please be positive and constructive.

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    33 Comments

    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?

    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.

    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: http://en.wikipedia.org/wiki/Capacitor

    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.

    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

    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

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

    user

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

    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.

    user

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

    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.