chiptroniks notes

lcd s creen components

Can laptop lcd screen be repaired ?


Good Evening All , Today in this blog post , i am going to unravel the answer to one baffling question , i have been asked many times by our stuents, our clients and many companies to whom CHIPTRONIKS provides consultancy .

Can LCD Screen be repaired if its not physically broken ? And we gave the answer “yes” . Finally after 1 year of research , CHIPTRONIKS now possess the technology of repairng LCD screens of Laptops/mobiles/LCD television , and we are soon going to lauch a full fledged 10,000 clean room fro repairing lcd screens.

Now let us understand how it works : I will give some glimpse of this , and if any body wants to start LCD screen repairing business, CHIPTRONIKS can offer consultancy in this :

Let us understand first :

Main Components of LCD screen :

•TFT/LCD Glass Substratelcd s creen components
• Polarizer Film
• Gate PCB
• Gate IC Driver
• Source PCB
• Source Driver IC
• Interface Connector (Flex
• Backlit Inverter
• CCF Lamp
• Diffuser,Lens Sheet,
• Light guide,Reflector Sheet

Machines Required for LCD Screen Repairing:

1. Bonding Machine
2. Laminator
4.Line Tester
5. LCD Panel Tester
6. Ionising Bar & Blow off Gun
7. Aging Test Chamber
8. Zero Clean Laminate Box
9. Clean Air Booths- Triple Boot
10. IC Driver Rework System
11.Test Tables
12. Color Analyzer
13. Polarizer Film Surface Detector

Concepts to Understand:

1. What is LCd Panel ?
2. What are major LCD Panel defects ?
3. What is cleanroom ?
4. What is an IC driver and its types  ?
5. What is Polarizer film ?
6. Optical measurement of a LCD Panel ?
7. What is ACF ?
8. How to use ACF ?
9. How to test LCD panels ?

What can be repaired? 

LCD Panel repair :
– Polarizer film replacement
– TAB,COG,COF bonding
– Backlight and LED repair
PCB repair
– Gate PCB repair
– Source PCB repair
LCD Display Repair

Main Points :

(a) Polarizer Film Replacement

The replacement of LCD Panel process consist of below stages;
– Disassembly of LCD Panel
– Detaching glass substrate from the panel and metal frame
– Removal of polarizer film (delaminating)
– Cleaning (using special chemicals) of glass substrate to the reapplication of the
new polarizing film
– Replacing polarizer film (laminating)
– Color Analyzer for optical test
• Removal and replacement of polarizing film need to be conducted
under stringent antistatic conditions (clean room environment).
• Panels placed in antistatic plastic bags.

(b)TAB,COF and COG Bonding

• The most common IC mounting methods are TAB,COF and COG.
• IC drivers provide the required current voltage needed to turn power
switching elements on and off.
• Horizontal or Vertical Lines on the screen are common failures caused by
failing driver IC’s and poor bonding to the conductive traces on the glass

(C) Bonding Process

The purpose of the bonding is to replace the defect IC driver from
the PCB and the LCD glass substrate.
• IC driver will be demounted from the LCD glass and the PCB.
• Connectors will be cleaned and examined under the microscope.
• LCD Panel will be checked by the ITO tester to find out if there is
an IC driver defect or an ITO line defect.
• If there is an IC driver defect, the IC driver bonding process starts
and new IC driver will be bonded on the LCD glass and PCB


The most common BLU related defects are;
– Diffuser sheet
– CCFL Lamp and LED
– Reflector sheet
– Light guide


lcd screen repair process chiptroniks

Bios password Removal


The following post has been taken from great Dogbert’s blog :

BIOS Password Backdoors in Laptops

Synopsis: The mechanics of BIOS password locks present in current generation laptops are briefly outlined. Trivial mechanisms have been put in place by most vendors to bypass such passwords, rendering the protection void. A set of master password generators and hands-on instructions are given to disable BIOS passwords.

When a laptop is locked with password, a checksum of that password is stored to a so-called FlashROM – this is a chip on the mainboard of the device which also contains the BIOS code and other settings, e.g. memory timings.

For most brands, this checksum is displayed after entering an invalid password for the third time:

The dramatic ‘System Disabled’ message is just scare tactics: when you remove all power from the laptop and reboot it, it will work just as before. From such a checksum (also called “hash”), valid passwords can be found by means of brute-forcing.

The bypass mechanisms of other vendors work by showing a number to the user from which a master password can be derived. This password is usually a sequence of numbers generated randomly.

Some vendors resort to storing the password in plain text onto the FlashROM, and instead of printing out just a checksum, an encrypted version of the password is shown.

Other vendors just derive the master password from the serial number. Either way, my scripts can be used to get valid passwords.

A few vendors have implemented obfuscation measures to hide the hash from the end user – for instance, some FSI laptops require you to enter three special passwords for the hash to show up (e.g. “3hqgo3 jqw534 0qww294e“, “enable master password” shifted one up/left on the keyboard). Some HP/Compaq laptops only show the hash if the F2 or F12 key has been pressed prior to entering an invalid password for the last time.

Depending on the “format” of the number code/hash (e.g. whether only numbers or both numbers and letters are used, whether it contains dashes, etc.), you need to choose the right script – it is mostly just a matter of trying all of them and finding the one that fits your laptop. It does not matter on what machine the script are executed, i.e. there is no reason to run them on the locked laptop.
This is an overview of the algorithms that I looked at so far:

Vendor Hash Encoding Example of Hash Code/Serial Scripts
Compaq 5 decimal digits 12345
Windows binary
Dell serial number 1234567-595B
Windows binary&source
Fujitsu-Siemens 5 decimal digits 12345
Windows binary
Fujitsu-Siemens 8 hexadecimal digits DEADBEEF
Windows binary
Fujitsu-Siemens 5×4 hexadecimal digits AAAA-BBBB-CCCC-DEAD-BEEF
Windows binary
Fujitsu-Siemens 5×4 decimal digits 1234-4321-1234-4321-1234
Windows binary
Hewlett-Packard 5 decimal digits 12345
Windows binary
Hewlett-Packard/Compaq Netbooks 10 characters CNU1234ABC
Windows binary
Insyde H20 (generic) 8 decimal digits 03133610
Windows binary
Phoenix (generic) 5 decimal digits 12345
Windows binary
Sony 7 digit serial number 1234567
Windows binary
Samsung 12 hexadecimal digits 07088120410C0000
Windows binary

The .NET runtime libraries are required for running the Windows binary files (extension .exe). If the binary files (.exe) don’t work out for you, install Python 2.6 (not 3.x) and run the .py script directly by double-clicking them. Make sure that you correctly read each letter (e.g. number ‘1’ vs letter ‘l’).

Вячеслав Бачериков has also converted my scripts to javascript so you can calculate the passwords with your browser: (sources).

Please leave a comment below on what make/model the scripts work. Also, be aware that some vendors use different schemes for master passwords that require hardware to be reset – among them are e.g. IBM/Lenovo. If you find that your laptop does not display a hash or the scripts do not work for you for whatever reason, try to:

  • use a USB keyboard for entering the password for avoiding potential defects of the built-in keyboard,
  • run CmosPwd to remove the password if you can still boot the machine,
  • overwrite the BIOS using the emergency recovery procedures. Usually, the emergency flash code is activated by pressing a certain key combination while powering on the machine. You also need a specially prepared USB memory stick containing the BIOS binary. The details are very much dependent on your particular model. Also, be aware that this can potentially brick your device and should only be done as a last measure.
  • Some dell service tags are missing the suffix – just try the passwords for all suffices by adding -595B, -2A7B and -D35B to your service tags.
  • The passwords for some HP laptops are breakable with this script.
  • Unlocking methods for some Toshiba laptops are described here.
  • Some older laptop models have service manuals that specify a location of a jumper / solder bridge that can be set for removing the password.

How to measure Laptop lcd screen size?


Screen sizes are normally measured in inches from one corner to the corner diagonally across from it. This diagonal measuring system actually came about because the early television manufacturers wanted to make the screen size of their TVs sound more impressive. Measuring your screen is quite easy: Learn more tips from laptop repairing institute;

  • Step 1 : Find the two points you will use for measuring your laptop LCD screen. The first point will be one of the screen corners — this is the corner of the screen, not the frame of the notebook. The second point will be the opposite corner from the first (for example, measure from the top left corner of the laptop LCD screen to the bottom right corner).
  • Step 2 Hold the end of your measuring tape down at the first corner of the screen, and extend the measuring tape until you reach the second corner.
  • Step 3 Read the hash mark on the tape measure at the point where the tape measure reaches the second corner. The number you see will be the size of your LCD laptop screen.

Some common Laptop LCD screen sizes are as under,

Laptopchip level problems & solutions Part no 3


1. Is there a “generic” current profile for laptops or does each laptop have it’s own unique
current profile?
2. In your example for DV9000, you say “0.01 – 0.3 -0.9 – 1.1 – 0.9 – 1.2 -1.45 then
display” Can you explain what happens at each current change state?
3. Do you need a power supply that logs the current or does it change slow enough to
visually monitor the different current states?
4. If a laptop gets power but no video, how do you isolate the failure between
northbridge, southbridge, SIO, bios?
1. Every laptop has its unique current profile. But although the reading is different, the
up and down (jumping) are similar.
2. The dv9000’s current reading may not very accurate; I suggest you first move the ram away
and see how the current changing, then put back the ram and check it again.
3. not very fast, your eyes can catch the changes.
4. this is a big question, may need a full text book to explain it. The simple answer for
this question: a. current reading, b. LPC wave, c.SMB wave. we have explain the current
reading before. LPC waves are measured on EC, if you can’t find LPC wave, that means no
communication between EC and SB, PLTRST present or not, if is not then SB problem, etc. SMB
waves are measured on ram slot, communication between ram and northbridge, H_RESET present
or not, if it is not then NB. There are also so many signals need to check.
I think the hardest fault for beginner is why the laptop not power up, not the faults after
it powers up.
lets see the example how we troubleshoot a non-powering machine,:
Model: Acer 5737
EC: kbc926
symptom: can’t power up
checked: 3ALW, 5ALW presented
1. check the power button has power or not, press it to see if pull down the voltage.<p>
2. check kbc926’s 32 pin, which is on/off see the signal received.
3. EC_VCCA is high?
4. check EC_RSMRST is high?
5. LID_SW# is high?
6. ACIN is high?
7. EC_CRY is correct?(32.76Khz)
8. South bridge crystal correct( which is X4, also 32.76KHz)
9. PBTN_OUT pull low when you press power button?
if all above have no problem, consider the south bridge fault. for this machine, there is a
single bridge – south bridge/north bridge/vga combined. North bridge’s functions are mostly
taken over by CPU.

#2. Finally i try to replace PU7 MAX8743 , and surprise the mobo try to power up , i removed RTC battery before testing and now when connect the AC adapter the FAN automatically start and mobo try to boot but only have 0.7v at PL22 , maybe i overheat max removing from old mobo , when mobo try power up max8743 get a little hot ,
Measure the resistance on PL22 PL23 you get 120 Ohms and 20 Ohms. Try also to replace PQ33 and PQ28
Now with the new max have present 3.3 v at LID_EC#. The motherboard should power on .


Laptop chiplevel problems & solutions Part 2


#1. mbx-165 with circuit protection problem

Sol: when the PQ20 -PUMB2 is not solder in the mobo i get the correct voltage 9v at gate in PQ26
DC_IN_G1 Same as the motherboard, the pq26’s G (DC_IN_G1) has 18V so DC_IN_R not present. DC_MOS_IN
is 18V, pq25’s G is 9V. So charging chip max1909 should be fine.First I check the AC_OFF_3#, which is very low, it should be high voltage.To check if there is other problem of the motherboard (I bypass the AC_OFF_3# signal, a
short cut or lazy way to fix problem), I fly a wire between pr188 and pq23’s third pin.
Now, the DC_IN_R has 18V, fine. but system standby power 3/5V is missing. touch the max8734
and find it very hot. Change it but still the same. i Use oscilloscope to monitor both pq64
and pq65’s pin 1, no wave or pulse to find when plug in power so max8734 never start to
work. check max8734’s 3 an 4 pin, find voltage is only 0.6v, something wrong here. This is a
signal call ALW_ON. Really hard to fix now, because ALW_ON involves too many components.
I decided to start from the simplest before moving up to EC or south bridge. Remove PD10,33
still same problem. Remove PD24, standby power comes up. Measure PD24’s 3 pin, only about 4
ohms so that is the reason, it pull ALW_ON low. Check schematic section of PU1 to PD24,
nothing important except control ALW_ON and AC_OFF_3#, so decide not to put pd24 back and
forget about rest. Try to power up and everything fine now.

#2. Motherboard start and load windows but i can hear a ugly noise from the cpu socket zone, the
max8734 is new but maybe something damage the max8734. I test with oscilloscope and the wave in PQ65 is
a little different between Motherboard fail and working Motherboard .
It is the inductors dry joint.

#3.can i replace this mosfet with ALPHA & OMEGA ao4427

Solutions:  yes, you can. every 8 pins mosfet has diode, what you saw maybe the ZD? don’t worry about
that. You saw FDS6675BZ , but not all have a diode between GATE and SOURCE , I see the two
datasheet and the arrow of diode is in different direction .

#4. How do you know when you need 5v to open this mosfet? i need more info about how works the
mosfets and transistor? what value need to check in datasheet to know what voltage needed at34
gate to open ?
On most schematic voltage ratings are specified 5,4v needed to open gate, checked voltage
with battery charged attached and there is present 5,4v…without battery and only ac
attached there is 0v,all other voltage are present, missing only acok voltage, usually on mos
datasheet the g voltage is present (it’s not a fixed voltage, is something between 3-12v
depending on type of mosfeet, on laptops usually it’s 4-5 volts).

#5.The eeprom is located in IC3201 , this is an ST microelectronic M24C08 W in TSSOP8 (DW) , i
will try to read whit WILLEM PCB 5 PROGRAMMER , have you any idea about decode the dump bin file
Before any hardware work, if phoenix bios based try crysis recovery first.

#6. I have an ACER with mobo COMPAL LA-3581 , i see that i have about 15-17 volts in the
POWER_SW button , not 3.3 usually , i think i need check the signal MAINPWON but im not sure
, i see MAINPWON is in LM393 IC , can you tell if the MAINPWON is the signal of the power
button? I remember in a HP probook i replaced LM393a whit LM393 and the power button have
also 15v , after this is solder a lm393a and goto 3.3v , now i know that lm393 and lm393a
are different.
Yes, for this mode of acer the power button should be about 17V.
Mainpwon and SHDN switch max8744 output on, so if you have 3ALW and 5ALW just don’t worry
about this signal.The signal of Mainpwon is combined from VL (LDO of max8744) and PACIN. LDO of Max8744 will
auto generate once Max8744 get power.
To switch off 3,5ALW output in battery mode (standby), it uses VS. VS comes from VIN. VIN is
0 when in battery mode. When you push the power button in battery mode(look at 51on# and
pq4), VS will come from b+++ and then output 3,5VALW.
I explain the usage of Mainpwon and VS. When you have
the power plug in, there should have high voltage in all 3 pins of pq4. B+ will be high,
because it is from VIN – actual B+ is the common point of external power and battery. VIN is
high. 51on# is high so the mos is in stop state.
If the power not plug in and battery present, VIN will be low and VS will be low too. VS low
will disable 3, 5VALW output, but to power up machine you need these 2 powers. 51ON# is the
signal to convert b+ into VS, when 51on# pull low the pq4 will convert B+ to VS therefore
Max8744 will output 3/5 valw.

#7. I have problem with acer 5920 mobo ZD1 , the lcd screen dont turn on , i have another 5920
38 working i see a problem in U1 AAT4280 page 18 , when ac adaptor is present in fail mobo have
about 1v in pin1 (OUT) but in the working mobo only have 0.30v , y check the diodes in
signal LCDVCC and are ok R10 is good also , and measuring resistance to gnd in pin1 in
working mobo is about 1M ohm and in fail mobo only give me a value if put tester in 200M ohm
scale , and the resistance start in 1-2M ohm and go up.
I will try to replace AAT4280 in a few days , what you think?
U1 has 1 input- on/off, 1 output – lcdvcc and 1 vin – +3V. The input are int_lvds_digon and
ev_lvds_vdden, the first one is for the motherboards that use intel integreted video and
second is for the motherboards that use mxm plug in video card. Only one of two can have
high voltage at a time, can’t be both high at same time.
In the normal working motherboard, the pin 6 should be 3V, the pin 3 should be but most be
the 3V. pin 1 should be 3V it is the power source for LCD.
If the pin 3 is low when you switch on the machine, the problem is either vga card or north
In your situation, you don’t need to check the resistance to the gnd unless you suspect u1
has been burnt. And also it has nothing to do with power supply.
the 3 things you need to check after machine power up:
1. pin 6 has 3V?
2. pin 3 has 3V?
3. pin 1 has 3V and LCD connector CN1’s pin 3 and 5 has 3V?

#8 .Now i have a satellite A100 , mobo INVENTEC SAN ANTONIO , the ac adaptor is 15v i test and
42 the Q519 is closed , have 15v at gate and 15v at source , but no power on +VBAT , the
charger is BQ24721 , VCC is good 15v at R619 but ACDET is only 1.3v and VREF5 is in 0 volt ,
you think BQ24721 is fail , or you can tell me other test before remove the BQ24271 ?
BQ24721 fails a lot, I usually change 24721 first.

#9. I have dv9000 QUANTA AT7 , not found AT7 schematic but AT6 match all , have voltje 19v fine
, also 3v and 5v present (max8734) and the power button have 3.3v , but when press power the
mobo don’t do nothing , no leds no fan , etc … i have also an AT3 working , i see in 1.5v
AT3 use MAX8717 and when AC adaptor is plug have 5v at DL1 and DL2 for gates PQ38 PQ35. Then
i go to AT7 and check DL1 DL2 for MAX8743 at gates PQ33 PQ28 , and only see 0 volt , maybe i
will try first to remove this 2 mosfet and check again ? this 2 mosfet dont seem short maybe
the MAX8743 is fail , what is your advice about this ?
First, there is nothing to do with pq28, pq33, those are for 1.5V output.
Second, check the EC working conditions when the machine can’t fire up. In those DV9000, pay
more attention on LID_EC#, this signal must be 3.3 before machine can fire up. If this one is
low, try to get 3.3V from somewhere to it.

i found test point T161 to check the LID_EC# , and 3v is not present
Capacitors on the graphic card are not so easy to fail, it only has about 5 ohm when you
Measure it, it is normal because internal resistance of graphic card just like that.
Once you find LID_EC# is low, you simply connect a power to it, let’s say the 3V power for
EC, connect a 10k resistor from 3V to LID_EC# pin. The purpose of LID_EC is let EC knows if
the lid is closed or not, once it is low the EC thinks the LID is closed and refuse to send
PWRBTN signal to south bridge, the PWRBTN is the signal invoke machine withdraw from S5
state and enter into S3 state, or people say switch on machine (actually, switch on machine
is pull up RSMRST – but RSMRST in most case is high, only after you remove the cmos battery
then it becomes low. So, when RSMRST is high and mobo wait for PWRBTN signal to become live
– this state we call it S5.)
#10.These capacitors are really burn in 0 Ohms , i replaced these 2 capacitors and now at TEST
POINT T161 have about 1v but still not trying to power , also i try put 3.3 at LID with a
external power supply and no way , the only see at the moment is DL1 and DL2 dont have 5v in
MAX8743 .
“Capacitors on the graphic card are not so easy to fail, it only has about 5 ohm when you
Measure it, it is normal because internal resistance of graphic card just like that.”

#11. Dell Inspiron 9400 aka E1705.
When i power it on all what i see is the power LED “green” turns on for 3 sec.
46 i tried everything, stripping all the drives and now i am down to only keyboard and one ram and still same
issue. tried it with bat and ac adapter
Take off the vga card and power computer, see if it still shut off.

#12. The circuit comprising PU11 (a TI TL331 single comparator), PQ62, PC195 and PD20 form a
charge pump circuit to provide a boosted +ve gate drive [VH28] to PQ61 (a large N-channel
MOSFET – top left of the schematic).
The circuit comprising PU11 (a TI TL331 single comparator), PQ62, PC195 and PD20 form a
charge pump circuit to provide a boosted +ve gate drive [VH28] to PQ61 (a large N-channel
MOSFET – top left of the schematic).
Without this gate drive, no DC input from the power adapter can be fed into the laptop.
Hence the sometimes flashing battery LED when the power button is pressed. There is enough
juice to power the system controller, but no feed to the charger.

Sol: i agree with you, such design is not only unnecessary but also worse than bad. what we did to
overcome this problem is replace pq61 with a diode, replace pq3 with another diode, of
course the condition to do this is battery charging part work alright.

#13.i have Toshiba satellite P200-1JV laptop. It runs on battery without any problem.
it does not run with a/c. does not charge battery.
when i plug in a/c without battery the a/c light on laptop blinks. press the power
button and nothing happens.
put battery in laptop with a/c power on, a/c light on laptop stops blinking and
battery charge light comes on but does not charge battery. press power button
and laptop will run until battery is exhausted.
the a/c charger is new and correct spec for laptop.
any advice on how to diagnose fault, like what area to check, mosfet, chips etc
first check all mobo marks to found mobo model and if you can found the schematic , then you
need to found one mosfet 8 pin sop8 that is connected directly to DC JACK , and then found
the next mosfet connected whit the first mosfet , when you conect AC you need this 2 mosfet
open , 19volts at DRAIN SOURCE , and about 8-10volts at GATE to open , usually is controlled
by the IC charger circuit , maybe have a short in AC circuit side or IC charger not
recognize the adapter and no open mosfets .

#14.i have managed to obtain schematic for Toshiba P200.there are two different sets of mosfets
controlled by two different charging ic.i like to confirm with you which one to test
if you check all you motherboard to confirm it is LA-3711P , then you need to start to
check PQ8 PQ9 , look for short after PQ8 between PQ8 PQ9 , if work fine with battery no short
on P3 B+ . then you need to have 19v at source drain in both mosfet and 8-10v at gate of
both PQ8 PQ9 pin4 , ACON PACIN control this gates , if you have 19v at pin4 PQ8 PQ9 the
mosfets are closed and then you don’t have the 19v at PQ9 pin5,6,7,8 that you need for laptop
to work with AC adapter.

#15.Charging problem
C700’s charging chip is 39A126, DV6000/9000’s charging chip is max8724 or max8725. Check the
working conditions of those chips. such as VIN, ACIN, ACOK, LDO, REF, SHDN.<p>
Charging problem is second hardest problem on notebook repairing, the first one is signal
level – everything looks ok but just no display.

#16.The first step to troubleshooting is monitor the current change. usually, current reading
can tell what was wrong and quite accurate.
You frequently mention monitoring the current change to pinpoint the area of failure. Can
you please describe this troubleshooting technique in more detail with some guidelines and
numbers to look for?
To understand why current changing, you may need to know the basic powering states of
notebook – which is called ACPI standard – S0 to S5.
S0 is full running state, S5 is state that after you switch off laptop but with either power
or battery presented. out off topic here, the S5 is the state after you shut down computer
not the state you just plug in the power. Power button is for wake up computer from S5 and
enter into S3. In ACPI standard, to switch on computers you need a signal “RSMRST”. It
explains why some laptops auto switch on if there is no CMOS battery, because its EC send
RSMRST when power plug in. But you need push power button to switch on laptop if there is
CMOS battery, because laptop remembers it is in S5 state.
Powering up a laptop can be divided into few parts, first check south bridge’s gpio
definition, check communication between bios and south bridge, check system ram, power cpu,
power up vga. so you can see the current goes up and down. step by step it reaches to full
Current changing monitor is just give you rough idea, sometimes not so accurate.
let’s see 2 examples:
1. a hp 530, power up but stay on 0.68A. it should go down a bit after 0.68A, and up again.
The faulty mobo current change is 0.02 – 0.3 -0.68. After we see this current, we know it
may have problem on SB or may be on NB but most likely is SB.
I check LPC 0 to LPC 3, no signal find. it may have problem on SB or BIOS. So I flash the
BIOS before I do anything on SB. It was fixed after I reflash BIOS.
2. DV9000. Normal mobo: 0.01 – 0.3 -0.9 – 1.1 – 0.9 – 1.2 -1.45 then display.
we find faulty mobo 0.01-0.3-0.9-1.1-0.9, by checking DMI Link we find there is one or two
pulses. So we have an idea that it already pass memory checking, the next stage is VGA
checking and active VGA output. In here, if it stop in 1.1 it most likely NB or SB problem,
but if it stop in 0.9 or after, it may be the problem of VGA.
Current changing gives you an idea about where is the fault but not 100% accurate. People
ask me what fault by just give me the current reading and I always say you need to give me
the changing states, how many jumps that current made.

#17.Toshiba satellite P200-1JV laptop. It runs on battery without any problem.
it does not run with a/c. does not charge battery.
first check all mobo marks to found mobo model and if you can found the schematic , then you
need to found one mosfet 8 pin sop8 that is connected directly to DC JACK , and then found
the next mosfet connected with the first mosfet , when you connect AC you need this 2 mosfet
open , 19volts at DRAIN SOURCE , and about 8-10volts at GATE to open , usually is controlled
by the IC charger circuit , maybe have a short in AC circuit side or IC charger not
recognize the adapter and no open mosfets

#18.Having problems whit dell xps M1530
Don’t do nothing when press power button , ACAV_IN is present at Q5 Q6 (3.2V) i have
DCBATOUT but 3v and 5v not present , i check DCBATOUT for U69 TPS51120 and is OK , then
check VREG3 VREG5 and also work fine , but i don’t have 3V/5V_EN to activate outputs , Q17 is
not in mobo only pads , D16 have 0.06v at 3V/5V_EN and 3.3v at PURE_HW_SHUTDOWN# , maybe
need S5_ENABLE to activate 3v and 5v ? what you think about the next step to check ? maybe
some signals in KBC WPC8763L .
At the moment the TPS51120 is working , use power supply to put 2.5V in D16 3V/5V_EN and
the 3V 5V outputs go enable . find why S5_ENABLE and 3V/5V_EN are low .

Laptop chiplevel problems & solutions Part 1


#1.Toshiba Satellite A205-SP4077, Core 2 Duo. While replacing cracked LCD tried several panels
with no success. Then noticed LVDS RX2- signal from motherboard is missing.
It is the north bridge dry joint, it is common fault of this model. Do BGA reworking on north bridge, and replace the north bridge if bga reworking doesn’t work.

#2. Machine: HP G6000(same mainboard as V6000)
Laptop will not power up.The machine has been water damaged. It does not have system standby power, which are 3V and

Solutions: Check Max8724(the battery charging chip) first, because to make system has standby power
this chip must work correctly. This is a 28 pin chip, we only need to test 1, 2, 4, 8, 10,7
11 pin. They are VIN(main power for chip), LDO(provide 3.3V for chip itself in order to set
REF voltage, also provide signal to drive 2 MOS to charge battery), REF(set reference
voltage of the chip), SHDN#(enable/disable chip, a switch), ACIN(indicate the power supply
has plugged in), ACOK#(power adaptor ok with mainboard).Everything ok except 10 pin, ACIN is 0V. This is incorrect, mainboard doesn’t detect there is an adaptor! Trace it backward and find it is very simple – mainboard use 2 resistors to
pull the input voltage(19V, directly from dc socket) down to about 4V, so test the first
resistor and find it opened. Change it and 3V/5V power come up and mainboard be able to
switch on.
Then the trouble start when I try to charge the battery. The charging current never go
beyond 0.15A and after 10 seconds the charging light start to flashing. Also can’t switch on
from battery. First, change Max8724, still same problem. Next check all the resistors around
max8724 and change it if it has any sign of watering, still no good. Then change
KB3926(EC/KBC, chip monitors the statue of battery), still same. This is the fault that I
never dealt with before.Decide to check MBDATA and MBCLCK, 2 signals that send battery information from battery to
KB3926 before I give up. I find the MBDATA is short!Finally, find there are 2 pins stick together on CN10(the connector of multimedia switchboard). Fix it and it start to charging battery. Switch on with power adaptor, ok. Remove
the power adaptor once switch on, battery keep the mainboard running, ok. But still can’t
switch on from battery once remove the power adaptor. Think, think, do I miss something here
or there? Oh, the CMOS battery not installed, put the CMOS battery back and everything work
perfectly. The battery part of troubleshooting takes me about 3 hours.
Remember, system may not run if you don’t have CMOS battery or CMOS battery is low for some
AMD cpu mainboard.

#3.I have problem with Toshiba S1900-102.I bought a new battery about 5 months ago, then the laptop did not work on battery and it’sstill at 35% and did not charge any I bought a used battery, and when I first connect it, plug the power cable and turn onthe laptop, I open Windows Power Meter. it’s work and begin charging till 60%, so I want to
try it I unplugged power cable and the laptop still works, and when I plug the power cable
again the Power Meter status said: AC Power. not charging I unplugged the power cable and
the laptop turn offI disassembled the battery to see what going on inside, I see M37516M6 microcomputer with a white shade around it.
Note: the second Battery still at 60% charge and didn’t increase or decrease

Sol: Most end users have no means to test battery. We test battery by monitoring the charging 10
current. The battery is ok if we see the charging current goes up, say to over 1A and hold
for a while. To check the battery condition, we firstly run the battery flat. Plug the power
supply which has current meter, see how long the charging current drop to normal standby
current. If we see it just take 30 min to drop to standby current, the battery may only last
10 min during normal usage.
In your case, I could not say what is wrong because I have to see if there is charging

#4.I’ve got a stuffed Toshiba Satellite A100 I’m trying to diagnose at the moment.
A100 as series has many different version, I don’t know which one you have. I just tell you
the common problems of this model.First, it does not power up at all. The charging light flashes and nothing on the screen. I
am still trying to find out what faulty of such kind.Second, it powers up but nothing on the screen. The power up sequence of working machine islike: 0.2A – 1.0A – 0.75A – 0.9A – 1.2A. Most time the faulty machines will stop at 1.0A or
0.75A, the cpu is not hot. In such case, the North Bridge does not send cpu rst signal to do
hardware reset. So this is north bridge problem.
Third, it only run on one memory.
This is also north bridge problem.

#5.HP pavilion dv5-1010tx
1) The computer overheats REALLY easily now
2) I use dual screens (laptop screen + Benq E2200HD via HDMI) and the external monitor will
occasionally flick. (every 10-15 seconds it will go black for half a second)

Solution: Yes, that is overload to vga chip.I still remember that back about 3 years ago I saw people modified their IBM Thinkpad, theyuse QXGA(resolution is 2048×1536) to replace original sxga(1400×900). The result of doing
this is vga chip get overheat and kill machine fast, usually not over one year. But for the
people can do such modify is no problem to fix their motherboard – resolder the vga chip, or
replace vga chip.The more calculation of vga chip carried, the more heat it generated. Think about how many
calculation jobs that vga chip has to do in your situation, not only the internal lcd, but
also the external lcd. Much more than those people change lcd from sxga to qxga.

#6.I have been repairing HpDVxxxx laptop with the video problem for a few years and havegotten very good at reballing/replacing the chip. I am now trying to figure out the NO powerat all or wont charge the battery EX Compaq C700 I have about 50 of these laptops will runon good battery windows shows it is charging the battery screen gets bright when you plug in20the ac charger goes dimm when you unplug it but it will not charge. I would like to know
what chip to start with I also have several DV9000 and dv6000 MB that do not get any power
at all. Any help on what chips to look at would be great.
C700’s charging chip is 39A126, DV6000/9000’s charging chip is max8724 or max8725. Check the
working conditions of those chips. such as VIN, ACIN, ACOK, LDO, REF, SHDN.
Charging problem is second hardest problem on notebook repairing, the first one is signal
level – everything looks ok but just no display.

#7.I would like to repair a system board in a compaq M2217AP (EE504PA) laptop. I believe theprotection circuit has failed and with my basic knowledge of electronics have located thefailed component. I require a copy of the circuit diagram or if you aren’t able to supply, a correct identification for part PC75. Can you assist?

Solution: PC75 is a capacitor, which is on the main power circuit. Luckily I have a such board in hand,
and I have checked where is the PC75 already. don’t worry about this capacitor, just take it
off if you think it is faulty. Pay attention to PQ24, PQ26, PQ25, PC68-70, PC16-19, PC48,
PC45, PC35, PC110-112. There is a guideline in here, all these components are located on
main power. There is also a guide when you check – check all the inductors and make sure
they are not short.

#8.The problem of machine is cannot power up at all.

Sol: Doing routine check:
1. system power: 3V, 5V all presented -ok
2. NBSWON signal: 3.3V presented – ok
3. press power button, NBSWON pull down to 0V, ok
4. check DNBSWON while press power button, no response. – problem.
in here I made a mistake, I didn’t pay attention of the voltage of DNBSWON, this mistake
waste me the next few days time. It should be 3.3V, but only about 1V.
Change EC as usual, because I thought the EC has problem. Then the big trouble comes – it
auto power up once I plug in the power but stop in 0.04A current. Check and find no S5_ON
signal, which indicate south bridge has problem, so change south bridge. But still same
problem and still no S5_ON. I was going to give up. I take a close look before I call
customer to say need to change motherboard, and I find that the EC I change is kb3926A
rather than kb3926C. In most case, this is no problem but in very rare occation…
So I find a 3926C and put on. Now the motherboard is back to the same problem while I first
start to check! So I change a wrong EC and this time I change a correct one, and also EC has
no problem!
Because EC will start to read bios once the power plug in(not as people think, once you
press power button). I check BIOS chip, BIOS_CS should have a countinue wave form but it
just one stright line. BIOS chip is faulty! Take me 3 days to find out. If I could think
more when I check DNBSWON, if I could checked BIOS_CS before I change EC, if I could
replaced with a kb3926c not kb3926a.

#9. Have you repaired any Compaq C700 laptops that will not charge the battery or run off AC
charger? You put in a charged battery and plug in the AC cord the blue light on the DC jack
will light up it says it is charging windows will show as plugged in and charging. But it
28does not if you remove the battery it will turn off. Plug in the charger with the battery
removed the Blue DC jack light will not come on. I have a stack of these that all do the
same. I am just now getting some time to mess with them. This is what I have found so far.
Putting a jumper wire from the DC Jack + wire to the first battery fitting (far left with
the laptop face down battery compartment away) this will let the computer run on the AC
power cord with the battery removed. I had to compare readings to a DV6000 as none of my
C700 will run on the Charger. The readings from a working DV6000 at the battery pins left to
right are (plugged in NO battery)
0v 3.35v 3.35v 0v 3.35v 0v
Battery plugged in and plugged to charger
12.36v 3.35v 3.35v 0v 2.26v 0v
C700 with AC cord and jumper wire installed
19.2v 5.56v 3.35v 0v 4.26v 0v
I have not tried putting in the jumper wire with charger and battery I do not know if it
would charge the battery or if it would blow up.there are thousands of these with the same issue so it is most likely the same problem onall of them just wondering if you have fixed any of these. But we have found solution
On the upper left right by where the DC jack plugs in there is a mosfet that on the working
board I get 19v on all 8 legs on the one with no power I get -.01v.
That is normal, it is a p channel mosfet – so control leg( the 4th pin) should be low
voltage. There is no power on m/b if you find this pin is high. But it also depend on the
verson of motherboard, with DV6000, some have n channel mosfet – in the case of N channel
29 mosfet the pin 4 must be high voltage. use p channel or n channel depends on protection
circuit. I can write you the info about how the power goes in and generate 3/5V system
standby power if you could tell me the motherboard project code.

#10 . No power on at all on some DV6000 motherboards.
Motherboard test readings
Dv6000 no power voltage test on good working board listed first then voltage on non working
These are next to MAX8734A chip 2 mosfets on left side this is good board
PQ39 mosfet 19.6v across one side all 4 legs
5.14 across the other side
Mosfet right beside it I could nor read the number
0v across the top side
5.14 across the bottom
On the other side of the MAX8734a there are 2 more mosfet side by side
The first one
PU10 19v across the left side all 4 term
3.39 on all 4 right terminals
The mosfet right by it
First 3 term on left are 0 v and the 4th is .07v
the other 4 terminals are 3.39v
The above readings are the working board not turned on but plugged into ac charger
NO the board that will not power on
PQ39 19.6 across the top 4
1.9v across the bottom 4
The mosfet right below it 0v across the top 4
1.9 on first 3 and 1.6 on last
18.26 on the left side 4
.05 on the right side 4
The one beside it
0v on the 4 on left
.05 on the 4 on the right
DV6000 no power
Max8734A readings good board
Top side Left to right
0v 0v 0v 2.0v 0v 0v 2.0v 0v 0v 0v 5.0v 5.0v 0v 0v
Bottom side Left to right
5.13v 5.13v 1.36v 5.13v 0v 18v 5.16v 3.40v .07v 3.4v 3.39v 3.38v 8.03v
Board with no power
Top side left to right
1.6v 0v 0v 0v .19v 0v 0v 0v 0v .17v 1.89v 1.83v 0v 0v
Bottom side left to right
1.65v 1.39v 1.68v 0v 1.66v .04v 0v 0v 0v 0v 0v 0v 0v 1.45v
You can check the datasheet of max8734, 20 pin is VIN – should have 18V input, after you
have 18V input the chip will output a 5V and send to pin 3 and 4 to switch on the chip to
output 3.3V and 5V.
To solve the board with no power, first you have to make VIN to max8734. I don’t think
max8734 has problem in here, problem is in some other place.

BGA Chips & BGA rework Stations Deciphered !!


Dear All ,

I am Vipin from CHIPTRONIKS (India), and i am writing this article in order to clear some important concepts of bga rework stations, bga chips and their compatibility.

IR & Hot Air : Honestly speaking  GO for high power IR bga machine like RE8500 , more power and complete IR. You can also opt for Scotle brands , as they are semi IR.

Lead Free/Leaded

Its best not to use lead free balls for a lead based solder ball IC as this will damage the chip as higher temperature’s needed for lead free. For lead free chips you can use lead based solder as this will not affect them as lower temperature is needed for lead based solder. Also this will make the repair more reliable as lead based solder isn’t so much affected by thermal cycling (regular and repeated heating and cooling of the chip during use of laptop). when i started my repairing business by seeing the ICH (south bridge) from intel chipset starts with “FW” for lead & “NH” for lead free.

How to tell BGA Chip is new or refurbished ?

To tell if it is new, you need to inspect under microscope to look for scratches, residue, and knicks. New chips are flawless. The under surface is also usually shiny and not dulled by a reflow. Also, most reballed chips are 63/37 balls. factory new would have lead free solder.

List of  BGA Chip which can be replaced with each other without Problem:

As Our company operates one of the biggest service centre with hudreds of laptops repaired fortnightly ,we have tried number of combination which successfully works. This list is purely ours and we do not guarantee 100 % but still i can say it will work ,as al i have tried personally. Even though CHIPTRONIKS is the biggest stockist of ics in the market , but still sometimes we also have to work in alternatives.

AMD/ATI Radeon parts 216-0674022 0674024 0674026

G86-750-A2 was in a Sony Vaio Laptop, replacing it  G86-770-A2 works fantastic.

G86-300-A2–> G86-731-A2 G86-730-A2

G86-302-A2 G86-731-A2 G86-730-A2

G86-303-A2 G86-731-A2 G86-730-A2

G86-602-A2 G86-631-A2 G86-603-A2, G86-620-A2, G86-630-A2

G86-603-A2 G86-631-A2 G86-630-A2

G86-620-A2 G86-631-A2 G86-630-A2

G86-625-A2 G86-635-A2 G86-630-A2

G86-630-A2 G86-631-A2

G86-631-A2 G86-631-A2 G86-630-A2

G86-635-A2 G86-635-A2

G86-703-A2 G86-731-A2 G86-730-A2

G86-730-A2 G86-731-A2 G86-730-A2

G86-731-A2 G86-731-A2 G86-730-A2

G86-740-A2 G86-731-A2 G86-730-A2

G86-750-A2 G86-771-A2 G86-770-A2

G86-770-A2 G86-771-A2 G86-750-A2

G86-771-A2 G86-771-A2 G86-770-A2

Le 965GM for LE82GT965

Secret :
If one solder G86- 770-a2  instead of 730, you must put in 64-bit mode, disabling half of the VRAM.
If you encounter resistance R133 in the plate, remove and R112 instead solder.
If R133 is not present, then take a 10k resistor and solder at position R112.
The line MIOBD9 sets whether the chart was 64, or 128 bits, there will the graph 3V in 64 bits.
This method can also be applied when we have a failure of VRAM. If we are lucky that the fault is in the middle of the VRAM off, it is preferable to do this, instead of 8 chips reboll.



he photo shows the replacement of resistance has to be able to use the 128-bit chips (G86-731-A2 128 bit version, G86-750-A2 G86-751-A2, G86-770-A2, G86 -771-A2).

In this case the resistor R133 was not present (indicated by lower needle) and had to be welded only 10K resistor R112 (in the upper needle pointing)

So i think this article will help solve some bga related queries . If you have any issues , you can comment.

How to Check LCD Screen Manufacturer ?

Good Evening Everybody,
I am  Amit ,senior engineerat CHIPTRONIKS ( VD Intellisys Technologies Pvt.Ltd) . Often our clients ask for lcd screens from us ,as we are leading supplier of lcd screens. So today i came to write this article . If you have any problem or requirement do call us at 011-43464998.
To find out LCD screen model number you need to take the screen out of the laptop and check the back of the LCD screen. On the back side of the screen you can see one or several labels with numbers. 99% of the screens on the market today have manufacturer’s code and screen size included in the model number. For example, screen model number LTN154AT07means that the screen is manufactured by Samsung and this screen’s diagonal size is 15.4-inch. Below is a list of LCD screen manufacturers with their abbreviations:
Acer – L
AU Optronics – B
Chi Me – N
Chunghwa – CLAA
HannStar – HSD
Hitachi – TX
IBM ( IDTech) – IT or IA
LG Philips – LP
LG Display – LP
Matsushita – ED
Mitsubishi – AA
Quanta – QD
Samsung – LT or LTN
Sharp – LQ or LM
Sanyo / Torisan – TM or LMJK
Toshiba – LTM or LTD
Unipac – UB

If you have difficulty determining model number of your old screen please ask us. It would be helpful if you could upload a picture of the back of the original screen with labels in focus and numbers legible. Support team will send you a link to a correct screen.

Sometimes it can be difficult to locate the right number or to recognize it. Please submit picture of the back of your original screen for our review following these guidelines:
1. Full shot of the back of the screen
2. Focus on labels or printed numbers
3. Focus on connectors

repairing dead laptops


Troubleshooting “DEAD” Laptops

Our Service Centre CHIPMENTOR repairs around 100  laptops a week and today we will decipher the myth surrounding the dead laptops .  Some of our steps have been taken from internet for more description

“Dead” means a different things to different people but usually means from truly dead to “No Display”

We will have  4 different versions of “dead” laptops  and  It always includes NO DISPLAY

1. No indication of viability – no lights – no fans – cool to touch
2. No indication of viability – no lights – no fans – warm or hot to touch
3. Lights – fans come on – lights don’t follow normal boot sequence (no flicker – usually stay on)
4. Lights – fans come on – lights follow normal boot sequence – appears to boot with no display

Depending on the conditions , you will require basic digital multimeter to BGA Rework station for solving these problems. You will also require laptop battery tester and list of ics with you . If you require any ics/tool/ you can contact 011-43464998.

For a laptop exhibiting symptoms under condition 1.
Step 1: Remove battery – test in another laptop if possible
Step 2: If you have another battery try it
Step 3: Test laptop for power up without battery
Test power adapter with DMM– usually measure 19 volts but check the label on the adapter .

If the above doesn’ts olve  the situation

Open the laptop so you can get to the location where the power adapter receptacle
attaches to the motherboard – with power adapter plugged in check for voltage on the
motherboard – if you have 0vdc replace the connector( usually called DC  power jack). This requires soldering and bit of expertise . If you are not expert try our Isolder40 .

If you have somewhere between 0vdc and 19vdc something is loading down the power
adapter – try a second power adapter – if it still measures out of range – unplug everything
from the motherboard ( memory – fans – hard drive – DVD/CD – wireless nics – video cable-
memory) – if measurement is still unchanged you have a bad motherboard replace it – if
voltage comes up to spec than one of the items you unplugged is causing the problem –
replace them one at a time until you identify the defective component . In this case you need to trace the entire motherboard measuring voltages at specific point.

For a laptop exhibiting symptoms under condition 2.

1.Remove battery – test in another laptop if possible
2.If you have another battery try it
3.Test laptop for power up without battery
4.Test power adapter with DVM – usually measure 19 volts but check the label

If the above doesn’t solve  the situation

Open the laptop so you can get to the motherboard – identify the source of the heat – it will
usually be in one of 4 areas – dc connector – CPU – GPU – screen inverter

If you have somewhere between several vdc and 19vdc something is loading down the power
adapter – try a second power adapter – if it still measures out of range – unplug EVERTHING
from the motherboard ( memory – fans – hard drive – DVD/CD – wireless nics – video cable –
memory) – if measurement is still unchanged and you still have a warm area consider
CPU could be replaced or removed and make another voltage check

GPU may be unsoldering its self from the motherboard (caused by poor design or excessive
heat) – pressing on it with a finger while powering up may fix the problem – if it does either
have the GPU reflowed or replace the motherboard . For this you will require bga rework stations

Hot areas around the dc power connections can be a bad power connector (worn out raises
resistance and causes heat) or failing components in the motherboard power conditioning
circuits – replace the power connector or motherboard as necessary

LCD Inverter – powers the screen – if it’s hot they are relatively cheap to replace – this supplies
the power to operate 1 or 2 fluorescent type lights that backlights the LCD – will not be present
on an LED type display

For a laptop exhibiting symptoms under condition 3.

Step 1:Remove battery – test in another laptop if possible
Step 2:If you have another battery try it
Step 3:Test laptop for power up without battery
Step 4: Test power adapter with DMM – usually measure 19 volts but check the label

If the above doesn’t solve the situation

Unplug from the motherboard (fans – hard drive – DVD/CD – wireless nics – video cable)
Open the laptop so you can get to the motherboard – GPU may be unsoldering its self from the
motherboard (caused by poor design or excessive heat) – pressing on it with a finger while
powering up may fix the problem – if it does either have the GPU reflowed or replace the

CPU could be replaced for a test
Replace memory for a test

For a laptop exhibiting symptoms under condition 4.

Laptop is probably booting with a display failure – usually inverter
After the laptop is turned on examine the screen CLOSELY for a VERY dim display
If you don’t see anything – shine a flashlight on it and examine it for a display

If one of the above is true (very dim display) check the invertor input plug for ~90vac – if ok
replace inverter – if that doesn’t remediate the backlight the fluorescent tube is defective –
replace it or the whole LCD if you are not mechanically inclined to replace them

If you don’t have ~90vac to the inverter plug check that the plug on the other end is firmly
plugged into the motherboard – if it is replace the motherboard as the inverter power supply is

If there is not even a VERY dim display as above then –

Hook up a an external monitor to laptop then power on – if you have a display check / replace
the following order

LCD video cable plugged in on BOTH ends
LCD cable replace
LCD Panel replace
Motherboard replace

Hook up a an external monitor to laptop then power on – if you don’t have a display check /
replace the following

Motherboard replace

WARNING – NOT ALL LAPTOPS AUTOMATICALLY SHOW A DISPLAY ON AN EXTERNAL displays – you may have to let it boot up and test with the keyboard video switch i.e.:FN+F2 etc

list of blue screen error codes


A Blue Screen of Death (BSOD),  is technically called a STOP error. It occurs when Windows suffers a serious error and is forced to “stop” completely.

Since a blue screen error gives you no choice but to restart, troubleshooting it  can be difficult.  Every STOP error includes a STOP code that can we can research to fix the problem.

STOP Error 0x00000001 to STOP Error 0x0000005F

Complete list of STOP codes from STOP error 0x1 (0x00000001) to STOP error 0x5F (0x0000005F).

STOP Error 0x00000060 to STOP Error 0x000000BF

Complete list of STOP codes from STOP error 0x60 (0x00000060) to STOP error 0xBF (0x000000BF).

STOP Error 0x000000C1 to STOP Error 0x0000011D

Complete list of STOP codes from STOP error 0xC1 (0x000000C1) to STOP error 0x11D (0x0000011D).

STOP Error 0x00000121 to STOP Error 0xC0000221

Complete list of STOP codes from STOP error 0x121 (0x00000121) to STOP error 0xC0000221.


STOP error 0xDEADDEAD means that the user deliberately initiated a crash dump from either the kernel debugger or the keyboard. STOP code 0xDEADDEAD may also display “MANUALLY_INITIATED_CRASH1” on the same STOP message.

  • Get in Touch

  • Our Excellent Training

  • Chiptroniks Classroom

Go to Top