Step By Step Troubleshooting Of No Display Problem In Laptop Motherboard
How to Solve Power-On No display Problem?
Problem - Laptop is getting Power-on but the display is not coming.
Solution - This type of problem where Laptop is power-on but no display can be solved by following simple steps.
First, we must understand the condition of the problem and how to check the motherboard for this type of fault. The type of fault can be determined by connecting the power supply or DC supply to the motherboard. The current or load on the DC supply indicates the condition of the motherboard whether it is the "full-on" condition or the motherboard is in "dead condition".
The current taken by the laptop motherboard depends on the generation of the CPU used as well as the load on the system. In Full-on condition when the display is coming maximum current is taken by the motherboard ranging from 350mA to 1A.
Depending upon the generation of the CPU used in the motherboard the current taken under Full-On condition can be as follows:-
1) Core-2-Duo >> 1A and above in full-on condition and display available.
2) Core i3 Generation 1 & 2 >> Above 650mA in Full-on condition and display available.
3) Core i3 Generation 3 >> 550mA - 600mA in Full-on condition and display available.
4) Core i3 Generation 4 & 5 >> 450mA - 500mA in Full-on condition and display available.
5) Core i3 Generation 6 & 7 >> 350mA - 450mA in Full-on condition and display available.
NOTE:- In general, it can be observed from the above data that as the generation of the CPU is increasing i.e as we go for the latest generation system, the current requirement of the motherboard is also getting reduced. Hence, the heating problem is reduced in the latest generation system.
The generation of the CPU can be observed from the motherboard or the schematics of the motherboard. The list is given below:-
* Nehalam is Generation 1.
* Sandy Bridge is Generation 2.
* IVY Bridge is Generation 3.
* Haswell is Generation 4 (SOC (system on chip) structure started from this generation).
* Broadwell is Generation 5.
* SKY LAKE is Generation 6.
* KABY LAKE is Generation 7.
* COFFEE LAKE is Generation 8.
>>> Now we will solve the problem of Power-on No display step by step:-
Step 1 - Connect the faulty motherboard to the DC supply and check the load, if the load is not as per the above listing then check CPU and CORE Section.
Step 2 - If the Current showing on DC supply is as per Full-on condition i.e Ok then try to replace and check CPU and RAM, and check whether a display is coming or not.
Step 3 - If after replacing CPU & RAM display problem is not rectified, then try to reflow the motherboard at 125*C after removing RAM and CPU. If the display is coming then the problem is solved.
After the above three steps if the problem still persists then we will go into signal and voltage level checking of the motherboard.
Step 4 - Check "PLTRST" (Platform Reset) signal coming or not. This signal can be checked on the Pin no. 22 of Wifi slot in older generations and on pin no. 44 for the latest generation motherboard. If PLTRST not coming then check the PCH_PWROK signal coming from SIO to PCH.
It has two cases:-
Case(a) PCH_PWROK not coming then check "VRM" or "CORE Section" and VRM PGOOD signal coming or not and troubleshoot for that section. Check whether a display is coming.
Case(b) PCH_PWROK coming then doubt is on PCH try to change PCH and Check whether the display is coming.
Step 5 - If PLTRST is coming then check 33 Mhz Clock coming at SIO or not. If the Clock signal is not proper then check 25 MHz Crystal. If it has any glitch then rectify that section and check for the display working properly or not.
Step 6 - If 33 MHz clock signal is coming smoothly without any glitch then check the Frame signal coming at SIO from PCH is proper. This "Frame" signal confirms that the CPU is responding to the data for the display interface. If the Frame signal is not coming then try to change the CPU and PCH and check for the Display on the external screen or keyboard and also monitor the load at the DC supply for the full-on condition.
Step 7 - If the Frame signal is coming properly then check the "CS" (chip select) signal coming at PIN No.1 of BIOS. It is an "#" or "Active Low" signal. If this reset signal at BIOS is not coming and all other inputs up to this point are ok then PCH is doubtful try to change the PCH and check for Display.
Step 8 - If the "CS" (chip select) signal coming at PIN1 of BIOS is OK and the display is not coming then BIOS data or firmware is expected to be corrupted. Try to Program BIOS and clean its ME region and re-upload the firmware. Keep in mind sometime the BIOS of a particular manufacturer will only run on a system.
After following the above steps 90% chances are there that the power-on No display problem of the laptop motherboard will be solved. But the remaining 10% problems could be due to the LVDS section or the Display connector also the supply voltage of the Display section which we will discuss in the upcoming short blogs that will be specifically focussed at the LVDS section of the laptop motherboard. Also, you will understand the signal flow of the display section and the power sequence in the motherboard.
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