Capacitors in motherboards
Capacitors are electrical devices that are primarily used in electronic circuits to store electrical charge. The construction of a capacitor involves two electrical conductors separated by a dielectric. The motherboard, a Printed Circuit Board (PCB) holding crucial electronic components of the computer systems, contains electrolytic capacitors. Tantalum capacitors are used to filter out noise on the power supply lines. They are used as a part of Voltage Regulator Module (VRM) to ensure delivery of smooth regulated power to the CPU so that it operates correctly.
Bad capacitors
Capacitor plague is a problem which arises due to failure of electrolytic capacitors. If the electrolyte used is poorly formulated it turns bad after some time and causes excessive internal heating. This heat in turn causes swelling of the capacitor and leakage of the electrolyte. In severe cases, the capacitor explodes.
Identifying the faulty capacitors
If the motherboard is having bad capacitors, the problem can be easily identified by observing some system faults or physical faults. The most common operational sign is that the computer and making memory errors and spontaneous reboots. Moreover, physical signs include irregular bulging of the peak of the capacitor, brown ooze and strange odor.
Recapping
Once bad capacitors are identified, they can be replaced by performing a labor intensive task. Replacing of motherboard capacitors is generally referred to as ‘recapping’.
Equipment required
The first essential step for recapping is to gather the right equipment, the unavailability of which may cause serious damage to the motherboard. Gloves, soldering iron, cutting plier, safety glasses, rosin core solder and required quantity of new and adequate value replacement capacitors should be available before start equipping motherboard with new capacitors.
Marking bad capacitors
Next, the motherboard should be explored carefully for bulging or oozing capacitors.
Making a schematic
One very important thing to be kept in mind while obtaining the new capacitors is that they should be of the same capacitance rating as the ones that are to be removed. Before desoldering is started, it is required to note the direction of the gray colored band on the capacitors carefully. The best practice is to make a diagram of the position and value of the capacitors.
Prepare the board
There are also chances that bad capacitors may burst while removing so eye protection should be put on. Also, CPU, RAM, Heat Sink/Fan, cards and all such devices should be removed from the board. The board should be cleaned.
Removing bad capacitors
Once all the precautionary measures have been taken, bad capacitors can be desoldered. In order to remove the capacitor, its leads should be heated one at a time at the rear of the board such that the soldering iron is in contact with the lead and the pad around the hole. The capacitor can be pushed and removed from the board then. This process requires the iron to be hot enough. The holes on the board should be cleaned before inserting the leads of the new capacitor. The diagram should be checked for placing the new capacitors with correct polarity.
Equipping the board with new capacitors
The leads of the capacitors should be neatly soldered by feeding small amount of solder into the holes. Excessive care should be taken to avoid making motherboard connections short. Once soldered, the leads should be clipped at the rear of the board. Next, the removed devices should be placed back and power can applied to test if the process of recapping was fruitful.
References for the pictures:
http://www.tomshardware.com/reviews/fixing-motherboard,1606-9.html
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