Short Circuit Repairs in Laptop Motherboards

What is a short circuit?

A short circuit is an electrical fault that occurs when a low resistance connection is established between the positive and negative terminals of a power source, resulting in a large amount of current flowing through the circuit and potentially damaging components or causing electrical fires. Short circuits can be caused by failed components or bad connections, and are often the result of components being damaged by excessive current, liquid, or wear and tear over time.

Types of Short Circuits

There are 2 times of short circuits in laptop motherboards;-

1. Main rail short circuit

2. Partial short circuit

Main short circuit

The main short circuit is when a motherboard has a short component that is connected directly to the main power rail, that’s the 19V in PC and 8V in MacBook.

In this situation, the motherboard will not turn on or do anything, nor charge or indicate any light. The main short issue is one of the easiest faults to diagnose and fix, and in our upcoming lessons, you will see how it's practically done.

Partial short circuit

A partial short circuit is a condition where a motherboard has a short component on the secondary power rail. Secondary power rails are volts that a made out of main volts. Examples of these volts are 3.3 SO and 5V S0. These secondary volts only turn on after the laptop is turned on, whereas main volts turn up as long as the charger or battery is connected.

A laptop with this condition may turn on and off or turns on with blinking LEDs depending on the section affected by the short circuit.

Signs and Symptoms of Short Circuit Issues in Laptops

Laptops that have a short circuit to ground will show different signs that can give you a hint before disassembling the laptop housing. Below are some of the most common signs of short-circuit laptops:

The charger light goes off when plugged into the laptop.

This symptom is very easy to observe, especially in Dell laptop chargers that have a ring of light around them. The light goes off immediately when the charger is plugged into the laptop. This is an indication that the laptop probably has a short circuit component in the main power rail. In other laptops that have a small light indicator on the charger, the same thing happens when the charger is plugged into the laptop and turns on after disconnecting and connecting the charger from the wall socket.

The charger voltage goes off after plugging into the laptop.

This symptom is almost the same as the previous one, however, this is effective in chargers that don't have a light. When you use a multimeter to measure the charger voltage before plugging it into the laptop and then measure zero after unplugging it, that is an indication that your laptop has a short circuit on the main power rail.

Heating components.

When you feel a specific component heating up on the motherboard, that is an indication of a short circuit. However, you should be vigilant because there are components that heat up normally when working, such as the CPU and onboard graphics card. We will see how to differentiate them in the follow-up chapters.

Burnt parts and smoke.

Whenever you see something burnt either on the motherboard or the housing, that might be a clue indicating a burnt short circuit component, especially when the laptop is not turning on or behaving strangely.

Weird smell

Whenever plastic or any other material is burnt, it produces a weird smell. This is very common in laptops that usually emit such a smell when the charger is plugged in and the laptop does not turn on.

Capacitors Making a Beeping Sound on Both Terminals in Continuity Mode

This is the most common and easy way to detect short circuits. If you disassemble the motherboard and use a multimeter in continuity mode, measure components like capacitors. If you see both pins making a beeping sound with very low resistance, it's usually an indication that your motherboard has a short circuit. Remember, some components are pulled low to ground when power is not connected. Components like the CPU, chipset, and graphics chip, will make a beeping sound even when working fine. We will see how to determine the difference in our upcoming chapters.

The laptop turns on and off

The laptop motherboard turns on and then goes off after detecting a partial short circuit. This can happen repeatedly until the motherboard is fixed. However, you should remember that this condition can happen due to several reasons, including faulty software communications.

The laptop not turning on

This is usually obvious. Whenever your laptop is not turning on, the first suspect is a short circuit, given that the charger and other first stages of power have been examined and proved fine.

Capacitors are electronic components that store electrical charge and are commonly used in laptop motherboards for various purposes, including filtering, decoupling, and energy storage.

In the context of a computer motherboard, capacitors are often used around the central processing unit (CPU) and other Ball Grid Array (BGA) chips to protect these components from electrostatic discharge (ESD). ESD is the sudden flow of electricity between two objects with different electrical charges, and it can be caused by static electricity that builds up on the human body or other objects.

To protect against ESD, the capacitors around the CPU and other BGA chips are designed to seem like they are shorted to ground. This means that they provide a low-resistance path for any excess electrical charge to flow to ground, thereby dissipating the charge and protecting the sensitive components from damage.

In addition to protecting against ESD, the capacitors around the CPU and other BGA chips can also help to smooth out power fluctuations and reduce electrical noise in the circuit. This can help to improve the performance and stability of the computer system

Causes of Short Circuits

There are many causes of short circuits in laptop motherboards, some are man-made others happen naturally. Below are some of the common causes of short circuits.

Inrush current

When motherboard power supplies are turning on, they tend to draw excessive current more than they can handle, this inrush current gets induced into the motherboard which ends up shorting other components

Liquid damage

One of the most frequent causes of component short circuits in electronic devices is the presence of water. Water has a low resistance, which allows it to act as a conductor when it comes into contact with components of different polarities. When water comes into contact with a laptop motherboard, it can cause corrosion and damage to the components, leading to their failure. However, most motherboards have protective measures in place, such as underfill and coating, which can help to repair them if addressed within the first 24 hours after liquid damage has occurred.

Electrostatic Discharge

In a laptop motherboard, ESD can cause short circuits if the electrical charge is transferred to a component that is not designed to handle it. This can happen if the electrical charge passes through a conductor, such as a trace on the motherboard or a component lead, and causes an excess of current to flow through the circuit. The excess current can cause the component to fail or malfunction, leading to a short circuit.

To prevent ESD from causing short circuits in laptop motherboards, various measures are taken to dissipate the electrical charge before it can reach sensitive components. This can include the use of capacitors that are designed to seem like they are shorted to ground, which provides a low-resistance path for the electrical charge to flow to ground and dissipate. Other measures, such as the use of anti-static bags and wrist straps, can also help to prevent static electricity from building up on the body or other objects and causing ESD.

Fault or Fake chargers

Substandard chargers that give out unstable current and voltage, cause many short circuits on the motherboard. It's recommended to always use original chargers on the laptops to prevent short circuits.

Connecting components when the laptop is on

It is common practice among technicians and hobbyists to replace components on a laptop motherboard while the device is powered on or while the battery and charger are connected. However, this can be dangerous because certain areas on the motherboard, such as screen connectors, can have high voltage as long as the battery or charger is connected. Attempting to insert a screen cable into the connector while the power source is connected could potentially lead to short circuits due to the close proximity of the pins inside the connector. To avoid these risks, it is recommended to always shut down the laptop and disconnect the power source before replacing any components on the motherboard. Additionally, it is important to follow proper safety guidelines when working with electronics, such as wearing protective gear and taking proper precautions to prevent electrical shocks.

Motherboard overloading

Motherboard overloading occurs when a laptop is subjected to heavy tasks that it is not capable of handling, such as running resource-intensive games. This can cause the power supply to work harder in order to provide enough power to the CPU and graphics chip, potentially leading to stress on the power supply components. As a result, there is an increased risk of these components shorting to ground due to the high current. To avoid motherboard overloading, it is important to ensure that the laptop is capable of handling the tasks it is being asked to perform and to avoid placing too much strain on the power supply. It is also a good idea to regularly monitor the device's performance and replace thermal paste if necessary to prevent overheating or other damage.

Thunder Lighting

Thunderstorms can pose a risk to electronic devices, including laptops, due to the high voltage surges that can be induced into a building's power lines when lightning strikes. These surges can cause short circuits in connected devices and potentially damage or destroy them. To minimize this risk, it is advisable to disconnect electronic devices from the wall outlet during thunderstorms, especially if the building's thunder protection status is unknown. It is also a good idea to invest in surge protectors like UPS to help protect against voltage spikes and power surges. In the event that a device is damaged due to a lightning strike or power surge, you can follow the methods in this course to diagnose and fix the motherboard.

Poor Thermal circulation

Poor thermal circulation, such as using a laptop in a poorly ventilated area, can cause the internal components to become excessively heated. This can lead to short circuits and other damage to the laptop. To prevent this, it is important to ensure that the laptop has adequate airflow and is not used in a location where the fan outlet is covered. This will help to keep the internal components at a safe temperature and reduce the risk of overheating and damage. It is also a good idea to use a laptop on a flat, hard surface rather than on a soft surface like a bed, as this can help to improve airflow and prevent overheating. Additionally, it is important to regularly clean the laptop's fan and keep the device in a cool, dry location.

Old components

Over time, the components in a laptop may become less effective and more prone to failure, which can increase the risk of short circuits. This is particularly common in laptops that are more than 10 years old, as the components may have been subjected to a significant amount of wear and tear over their lifespan. To reduce the risk of short circuits and other issues, it is important to regularly check the condition of the laptop's components and replace them if necessary. This can help to ensure that the device is functioning properly and to extend its lifespan. Additionally, it is a good idea to keep the laptop clean and well-maintained, as dust and other debris can build up over time and interfere with the proper functioning of the components. Regular cleaning and maintenance can help to improve the performance and reliability of the device

Bad components

In some cases, even brand new laptops may experience short circuits due to faulty or substandard components. This can occur when the components do not meet the necessary quality standards or have defects that cause them to fail prematurely. This is evident in chapter 8 where i recorded a video fixing a 10th-generation HP laptop that had failed due to a short capacitor.

Connecting Short USB components’

The USB ports on a laptop typically have internal protective components that are designed to prevent short circuits from occurring. However, it is still possible for a short circuit to occur on the motherboard if a connected device pulls a high current that is too much for the protective components to handle. To minimize the risk of short circuits and other issues, it is important to use caution when connecting devices to the USB ports and to avoid using devices that are known to draw high levels of current. It is also a good idea to always first check the condition of internal USB pins while diagnosing a laptop because often broken USB pins can make a laptop malfunction.

Missing protection components

Some manufacturers may choose to omit certain protective components from their motherboards in an effort to reduce costs or to make the devices more compact. However, this can increase the risk of short circuits occurring during current surge conditions, as the protective components are not present to help prevent damage to the components. As a result, it is not uncommon for different laptop series to vary in terms of their strength and durability. For example, the Lenovo Thinkpad series is known for its durability and longevity, while the Ideapad series may not be as reliable. Similarly, the Dell Latitude series is generally considered to be more reliable than the Inspiron series. It is always a good idea to understand the model of the laptop you are repairing because this will help you choose the best approach while diagnosing and fixing them.

Audio ports

The connection of a laptop to a high-frequency sound system, such as an amplifier, using an aux cable can potentially cause the motherboard's sound chip to blow up and result in a short circuit. While this is a rare occurrence, it is important to exercise caution when connecting a laptop to external audio devices. As demonstrated in the picture in the background of this video, a Dell motherboard suffered a sound chip blow up due to this same condition. To prevent this from happening, it is important to advise customers to handle audio cables with caution and to avoid pulling or yanking on them, as this can cause damage to the connectors and potentially lead to short circuits.

Twisting and bending chargers when they are connected to the laptop

Bending and twisting a charger while it is connected to a laptop can increase the risk of an internal short circuit occurring. This is because the charging port has three connections - 19V, ground, and a current limit middle pin. Bending or twisting the charger can cause these wires to get connected leading to a short circuit. To reduce the risk of short circuits and other issues, it is important to replace deteriorating chargers and charging ports earlier on before total damage.

There are several tools that are commonly used in the diagnosis and repair of short circuits in laptop motherboards. These include:

• Multimeter

  A multimeter is a powerful tool in electronic design and repair. In laptop motherboard repair, a multimeter is used to detect short components using the continuity, resistance, and diode functions. To check for short components in continuity mode, the technician puts the multimeter knob in the continuity function and measures both sides of the component with the black probe on ground and the red probe on the positive side of the component. If the multimeter makes a beeping sound with very low resistance, there is a high possibility that the component is short to ground.

  
  

• Power supply

  A power supply can be used to detect the exact component that is short to ground by using the voltage injection method. Voltage injection involves injecting current into the short circuit rail. As current will flow through the path of least resistance, it will flow through the short component, causing it to heat up. It is important to be aware of the motherboard architecture in order to identify the over-current protection components, such as the MOSFETs near the motherboard power jack, which may also heat up while protecting the actual short component.

  
  

• Thermal camera

  A thermal camera can help to identify the exact component that is the source of the heat when using the voltage injection method. Thermal cameras can be expensive, but there are other affordable alternatives available, such as freeze spray.

  
  

• Microscope

  A microscope can be used to visualize small components clearly and to identify clues of short circuits or other component damage.

  
  

• USB current meter

  A USB current meter is useful for diagnosing faulty USB ports. A USB current meter with a digital screen will show the voltage and current being output by the port. A Type C current meter can be used to detect short circuits in laptops that use Type C chargers.

  
  

• Oscilloscope,

  An Oscilloscope can be used to visualize what is happening on the motherboard and to diagnose and fix short or partial short circuits, particularly in data communication lines.

  
  

• Soldering equipment,

  Soldering machines such as a soldering station, soldering gun, preheater, and solder wacky, are used to disassemble and replace short circuit components on the motherboard.