Replace Capacitor in Computer Board
by 11010010110 in Circuits > Electronics
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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
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
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
pin from message board
sharp soldering tool 30 W (more may be better but dont overkill) and soldering stuff
Find It
most bad caps have visible damage. the last image shows ok (green) and failed (red) capacitors
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)
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)
Remove Battery
before you start any work with the board remove the battery
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
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
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)
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)
Insert the New Cap
insert the new cap with the - in the same side as the previous one
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
try to make the drop on the outside as small as possible
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
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
Yay
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 ?)
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 ?)