laptop motherboard repair guide

Understanding the power sequence of laptop motherboards is very important. Firstly the power sequence is the exchange of voltages and signals between the motherboard chips.

Secondly, This happens before anything appears on the screen.

The power sequence is the phase in which the motherboard prepares itself to function. This phase consists of sending orders to different voltage generators from some ICs. Secondly, receiving confirmation makes sure the principal Integrated circuits of the motherboard are functional.

The power sequence should take place in a specific order. Secondly, if one signal or confirmation is not sent or received then this phase stops there and finally, nothing will work.

The power sequence is used to troubleshoot laptop motherboard problems by testing voltages because the absence of some voltages indicates problems with some ICs. Also in some schematics, the power sequence is described which makes troubleshooting easier.

Steps To Check Voltage And Signal Sequence For Laptop Motherboard Power On Stage

The steps are known as ladders for voltages and signals. These steps are given below.

ALWAYS VOLTAGE Checking

This voltage generates before the power on the button is pressed. 3Volt is given to SIO and EC BIOS.

After Pressing The POWER BUTTON

Once the power button presses SIO to inform PCH and turn buck converters one after another.

POWER ON VOLTAGES check

The voltage after power should be produced as given below :

• 3.3 Volt
• 5 Volt
• 1.8 Volt
• 1.5 Volt
• 1.05 Volt
• CPU CORE
• 0.9 GFX Core

POWER GOOD Signal Check

PCH receives SYS PWR OK signal confirmation signal saying all power is ok.

RESET Signal Check

PCH generates a PLTRST signal to clear motherboard junk values and reset the motherboard.

CLOCK SIgnal Check

CLOCK starts generating different frequencies according to the requirement of chips.

Starts Reading BIOS

In this step, the CPU starts reading BIOS.

POST Checking By Motherboard

In this step motherboard test all chips and devices in this process which is also called ‘Power on self test.’

Motherboard power states for understanding laptop motherboard power on sequence stages

These are the states of the laptop depending on the power consumption of the motherboard, you already know the two states which are :

1. You turn on the Laptop.
2. The laptop gets turned off by you.

The motherboard states are referred to in character ‘S…’ Where the x is a number between 0 and 5.

S0 State Of Laptop Motherboard

Working, the system is fully usable, all the components have their voltage.

S1, S2, S3 State Of Laptop Motherboard

Sleep, The laptop appears to be off, the laptop consumes less power than in S0 state, the RAM has its voltage, and is kept refreshed.

To wake the laptop from this Sleep state you need only to press a key on the keyboard or move the mouse.

S4 State Of Laptop Motherboard

Hibernate, the system appears to be off, and the power consumption is reduced to the lowest level. An image of the RAM is kept on the disc because RAM loses its voltages, to wake the laptop you need to press the power button.

S5 State Of Laptop Motherboard

In this step, the laptop motherboard gets shut down.

Types Of Motherboard Voltages For Power On Sequence Stages

There are four stages in the laptop motherboard which are given below:

Always Supply Voltage Type (ALWS or AUX or AL)

These voltages are always present even when the laptop is off, on one condition: the battery should be placed or the charger plugged in. Thises voltages are:

• 5 Volt DC
• 3.3 Volt DC

The 5 Volt and 3.3 Volt come from Voltage generator ICs in the motherboard.

Suspension Voltage Type (SUS ON)

These voltages are present in suspended or sleep mode (S1, S2, S3):

• 5 Volt DC
• 3.3 Volt DC
• RAM voltage (For DDR1 – 2.5 Volt, For DDR2 – 1.8 Volt, For DDR3 – 1.5 Volt, For DDR4 – 1.2 Volt)

Note that the 5 Volt and 3.3 Volt are not the same % Volt and 3.3 Volt is Always voltage, there is another voltage generator that generates those 5 volts and 3.3 Volt.

Power On Voltage Type (RUN) (S0 State)

All the components have now their voltages. There is a supply of 1.05 Volt and 1.8 Volt is also done.

CPU Core Voltage Type

CPU requires core voltage, for example, a high current of approximately 20 Amp to 30 Amp. The newer motherboard graphics chip is also integrated into the CPU. So the graphics Core voltage is also required. These voltages are GFX core voltages. These voltages are approximate:

CPU Core = 0.8 Volt to 1.5 Volt / 20 Ampere to 30 Ampere.

GFX Core = 0.8 Volt to 1.5 Volt / 10 Ampere to 20 Ampere.

Laptop Motherboard Power Plane

There are two power input sources in a laptop motherboard one is adapter input and another is battery input.

The adapter input and battery charging section are called VIN ( Voltage Injection) sections. This section decides which power needs to be sent inside. This section has another task called battery charging. there are a number of buck convertors used according to fulfill the requirement.

Laptop Mother Powe Plane To Understanding Laptop Motherboard Power On Sequence Stages

Knowing the motherboard model number is important to find the laptop motherboard power sequence. Especially when we try to find out the Laptop Motherboard Power Sequences.

It helps to find pictures, schematics, board views, and known issues. There is always a number written on the board itself. In some cases, there’s also a sticker that tells a variant.

Common Laptop Motherboard Manufacturers For Laptop Motherboard Power On Signals

Below are some of the common laptop motherboard manufacturers

Quanta

Quanta motherboard found is HP, Dell, Acer, Toshiba, and a few Lenovo laptops. The model number on the board is “DA0xxxxMByyy” (first 0 is optional), “xxxxx” is the actual model, and “yyy” contains the revision. For example DAY11AMB6E0 for Quanta Y11A rev E.

Compal

Compal motherboard found in HP, Dell, Acer, Toshiba, Lenovo. Secondly, the model number is “LA-xxxxP” (P is optional), the older, the lower the number is like LA-4082P from 2007 or LA-E541P.

LCFC

Found in Lenovo, it’s actually Compal. The model number is “NM-xxxx”.

Wistron

Found in Acer, Dell, HP, Lenovo. The model number is an “xxxx-x” (x being a digit), often associated with a name. For example “Ricjie MB 11241-1”.

Inventec

They make Toshiba, HP, and Some Acer motherboards. Secondly, their model is number is often “xxyyzz” with “x”  being a letter, “y” a digit, and “z” as the optional letter.

There is also a “6050xxxxxxxx-MB-xx” number that can be easier to spot. For example “SA10E” and “6050A2052401-MB-A04” for Inventec.

Foxconn

Foxconn motherboards are found in Sony, Some HP laptops. HP has a weird model number like “CHICAGO_HR_HPCMV_MB_V1” or “PM_I_HPC_S_MV_MB_V3”.

Sony comes with an “MBX-xxxx” number that’s easy to identify, and other numbers, like “MBX-202” and “M790”.

Pegatron

Pegatron motherboards are found in a few Acer and Toshiba motherboards. Acer, in general, has an “xxyyzz” with “x” being a letter, “y” a digit, and “z” an optional letter. Toshiba has a weird model number like “PLF/PLR/CSF/CSRUMA”.

Whereas the following manufacturers make their own boards (except maybe a few models here and there):

Apple

Apple board model number is “820-xxxxx”, like “820-3462”. It’s written black on a black surface so it’s hard to spot.

Asus

Asus board model number follows the same format as the laptop model number. Secondly, It can be the same or similar, and sometimes different.

MSI

MSI model number is “MS-xxyxz”, with x being digits, y a digit or letter, and z an optional digit for revision. Some boards have two different model numbers like “MS-16J5” and “MS-1795” (with a 1 appended for the revision.

Samsung

Samsung model number is the name associated with a “BA41-xxxxxx” number, like “Bremen-D” and “BA41-01197A”.

Clevo

Clevo manufactures laptops for a lot of “small local” brands. There are two model numbers on the board, “6-71-W25S0-D02” and “W251ESMB-D0”.

HanStar doesn’t Design motherboards so we did not put them on the list. But rather HanStar manufactures the PCB. “J MV-4” and “94-V0” do not board model numbers, they are generic markings about PCB characteristics.

List Of Laptop Motherboard Power On Signals

The following are laptop motherboard power on signals:

 

Signal Name And Description For Laptop Power On Signals

When power is connected either from the adapter or battery to the motherboard it passes from various stages.

Below mention a chart given signal name and their description.

 

Power On Sequence Diagram For Laptop Power On Signals

Below are the diagrams for laptop power on signals.

Laptop Power On Signals For General Motherboards

Below is the power on signals for general Motherboards.

Laptop Power On Signals For Quanta Motherboards

Below is the power on signals for Quanta Motherboards.

 

Laptop Power On Signals For Quanta 4th Generation Motherboards

Below is the power on signals for Quanta 4th generation Motherboards.

Laptop Power On Signals For Wistron Motherboards

Below is the power on signals for Wistron Motherboards.

 

Laptop Power On Signals For WISTRON 5th Generation Motherboards

Below is the power on signals for Wistron 5th generation Motherboards.

For making a career in laptop chip level repair you must have knowledge about basic Chip Level components too.

There is also a guide for desktop motherboard power sequence which is similar but much smaller compared to laptop motherboards.