LCD monitor boot black, dark like no backlight
This phenomenon is more general, backlight did not work, boot light in normal condition, but do not see the image. If you look at the screen, see on the screen is dark like, but no backlight.
The cause of the malfunction of such failures is the lamp does not light, we see a black screen, only dark like. Because the lamp, poor Inverter and +12 V power supply, the individual driver board ON / OFF signal sent.
Repair methods such failures should first check the ON / OFF signal is not synchronized drop if the ON / OFF signal is normal, check Inverter +12 V power supply is normal? +12 V power supply, check the high pressure plate and tubes. in the actual repair, one panel filter capacitor loss of capacity, will also appear the boot that is the fault of the black screen, no backlight is lit. when +12 V filter capacitor after the loss of capacity, easily lead to overheating the Inverter promote specifically to deal with the breakdown damage .
Inverter performance is good or bad, can be used directly regulated power supply test Inverter. Lamp is good or bad can be used a single lamp small mouth Inverter measuring tube one by one, to observe the operating current of the lamp lit. If a lamp operating current one is too big or too small, Zhezhi lamp.
The overhaul LCD display what oscilloscope
Oscilloscope of many different types, according to the measurement field and the requirements of the different Universal oscilloscope and dedicated oscilloscope. Points from the function, a analog oscilloscope (single-track, double-track, multi-track), sampling oscilloscopes, vector oscilloscope, digital storage oscilloscope. The standard overhaul LCD monitor selection oscilloscope what is it? Ability to compare two such as the phase of the signal to be measured from the Y channel bandwidth, sensitivity, whether synchronous function to consider the selection of suitable single track or double track general purpose analog oscilloscope, the conditions are good, the best selection of digital storage oscilloscope . Shown ATTEN produced analog oscilloscope and digital storage oscilloscope physical map.
LCD monitors overhaul to observe the waveform is generally switching power supply, inverter oscillation waveform the clock waveform output of the microcontroller PWM waveform, the bandwidth of the Y-axis is greater than the signal to be measured band width from the point of view should be used the bandwidth of the oscilloscope. However, due to the very high frequencies, a lot of liquid crystal displays waveform oscilloscope bandwidth is greater than a few megabytes, very expensive, therefore, the choice of the bandwidth of the Y-axis can be generic in ? MHz dual trace oscilloscope to meet the needs of the general maintenance.
Sensitivity, also known as the minimum vertical deflection factor to reflect the the oscilloscope test the ability of weak signal. Sensitivity to consider the selection of high sensitivity of the measurement of some weak signal. LCD Repair, selection of an oscilloscope, the sensitivity should be better than 10mV/div (this value is smaller, the higher the sensitivity), the best 10V/div, or 15V/div gear, so, you can use the LCD monitor 100:1 attenuation of the probe to measure the inverter voltage.
Liquid crystal display blank screen failure cause
LCD display black screen cause of the malfunction and repair ideas
Black screen for a variety of reasons:
First, the power circuit unusual cause: performance indicator does not light panel buttons no response,
12V voltage first check whether normally follow the investigation 5V voltage normal No, because part of the A / D driver board signal processing chip operating voltage is 5V, so the search can not be the fault of the machine, the first measure 5V voltage with a multimeter, if 5V voltage or 5V voltage becomes very low, then a possible problem is the input stage of the power supply circuit, which means that the 12V conversion to 5V power supply part of the problem, this failure is very common, and generally burned insurance or the regulator chip failure, some of the machines built-in switching power supply, output of the two groups of power, including a group of 5V for signal processing, and another group is 12V backlight with inverter point, switching power supply part of the circuit failure may possibly lead to two sets of power are not output. Another possibility is the 5V load increased 5V voltage is very low, to put it another way to say, a problem with the signal processing circuit, a part of the circuit is damaged, causing the load increases, the voltage of 5V pull low, one by one investigation level components of the problem, replace the faulty component, 5V returned to normal, the failure generally will be solved, but also often encountered 5V voltage can not be returned to normal after the normal boot, this case is how kinds of reasons, on the one hand the the MCU program was obliterated may lead to boot, there is the MCU itself is damaged, for example, the MCU I / O port damage, MCU scan can key encounter such a failure caused by the MCU find hardware is of no use, even if you change the MCU can not solve the problem, because MCU is the need for programming and write Mary, can not find the original AD, replace the driver board, we can find another way to find substitution A / D driver board on the market can buy a lot of places, if the local market to buy can not, you can post here to see (if not, give owners a message) Forum above There are a lot of LCD master, perhaps you can purchase the accessories you need and find the information you need.
The second situation is normal power supply, according to the panel's key reaction is also normal, and the screen is blank:
Encounter this failure is necessary to give full play to the maintenance staff attentive nature, careful observation, one by one investigation, keys normally work on the A / D driver board the MCU or can work properly, and will further illustrate the power part of the work or normal , black is not lit backlight, may drive the backlight circuit there is a problem, we first should display even to the host boot check carefully observed close to the screen, if you see a very somber picture of the show to prove the A / D driver board of the signal processing section of the circuit is normal, locked in driving a backlight inverter and controlling the inverter switch circuit (Note: inverter In fact, with the working principle of the switching power supply, it is the use of electronic switches charge and discharge control transformer coil, coil induction in the other group we need high voltage to drive the backlight inverter insurance burn caused no 12V supply and switch chip failure) inverter common faults, the other is the AD board failure, the cause can not output high to control the inverter switching feet on control inverter switch part of the circuit, with the negative multimeter table pen grounded is table pen connected to the control output pin, press the switch button, normal can be seen that there is power level change, can also be relatively simple method to determine the inverter is not good, it is the first to find control inverter switch the cord is connected directly to the 5V voltage, inverter failure generally can be lit backlight (Note: inverter three lines will be able to work, where two is the positive terminal of the 12V power supply and ground, and another switch control line.) Another cause black screen, that is, the screen's backlight bad, but if it is bad at the same dual-lamp and four-lamp screen backlight is unlikely, the bad one lamp can also cause black screen, but with black failure of the previous The performance is different, this is due to some G60-447CL inverter with unbalanced load protection If a lamp is broken, the power inverter to enter the load unbalance protection status, will flicker and then goes blank.
This is the situation I frequently encountered in the maintenance of LCD black failure here summed up, hoping to give our friends like maintenance reference.
LCD Repair general judgment
The following are some maintenance ideas based on our day-to-day maintenance of the summary:
1. Monitor machine without electricity
This is one that should be said to be very simple fault, the common extension within the general liquid crystal display power supply and the machine outside the power two, outside the machine.
Regardless of the kind of power, and its structure is simpler than the crt monitor power more fragile general are some small elements like a fuse, input inductor, switch, voltage regulator diode.
Relatively rare failure is caused by the motherboard cpu power does not start, this part is actually relatively simple principle, that is, by keying board to cpu, then through the cpu output a control signal to drive the power conversion ICs.
The display brightness is not bright, but the power indicator light.
This problem is generally the high pressure caused by abnormal, the protection circuit action, in this case, a general LCD display, see "strabismus.
The overhaul of the points is the contrast repairs.
Because inverter design of the present liquid crystal display are generally symmetrical design, while the both sides of the bad may substantially no.
The general old machine is easy to go wrong is a step-up transformer and lamp, new protection circuit and process.
3 the screen bright lines or dark lines
This problem, generally is the failure of the liquid crystal panel.
The light fault line is generally a cable is connected to the LCD body
The dark line general body of the screen there is leakage, the above two questions is basically a death sentenced to a machine, no maintenance value, because the price is too high of a screen.
4. Huaping or black and white
This problem usually a problem with the drive voltage of the screen, if the drive circuit on the motherboard of the screen, then it should be a motherboard failure If the drive circuit of the screen on the LCD screen, the general screen should be changed, maintenance risky.
5 color cast failure
General can enter the service adjustment mode to adjust.
Other relatively rare failure
Interference: in a different mode, the LCD monitor may be some interference, the majority is a normal phenomenon, few are brought in the circuit.
Special liquid crystal display production process, resulting in a problem was detected only in standard mode can be regarded as failure.
Display machine without electricity
(1) Power Failure: This is the one that should be said is a very simple fault, common LCD display extension power and machine outside supply two types of machine. Regardless of the kind of power, its structure is simpler than the crt monitor power more wearing the generally small components, like the fuse, rectifier bridge .300 V filter capacitor, the power switch, power management IC, diode of the rectifier output filter capacitors.
(2) failure of the driver board: driver board burned insurance or regulator chip fails, some of the machines built-in switching power supply, output of the two powers, one group is 5V for signal processing, and the other group is 12V the G61-511WM Inverter point backlights, switching power supply part of the circuit failure may possibly lead to two sets of power are not output, check the 12V voltage No good, followed by investigation 5V voltage good No, because the a / D driver board MCU chip voltage is 5V, so find can not be the fault of the machine, be measured with a multimeter 5V voltage, if there is no the 5V voltage 5V voltage becomes very low, then a possible problem is the input stage of the power supply circuit, which means that the 12V conversion to 5V of power supply part of the problem, this failure is very common check 5 terminal regulator block (common models 8050SD-LM2596-AIC15-01, etc.).
Another possibility is the 5V load increased 5V voltage is very low, to put it another way to say, a problem with the signal processing circuit, a part of the circuit is damaged, causing the load increases, the voltage of 5V pull low, one by one investigation level components of the problem, replace the faulty component, 5V good recovery, the failure generally will be solved, often encounter 5V voltage also not good to restore good boot, this case is how kinds of reasons, on the one hand be washed away MCU procedures may lead to boot, there is the MCU itself is damaged, for example, the MCU's I / O port is damaged, the MCU scan can not button, to encounter such a failure caused by the MCU find the hardware is of no use, even if you change the MCU can not solve the problem, because MCU is needed programming and writing code, can not find a the original AD driver board replacement case, we can only Universal driver board A / D substitution: 151D or 161B.
Inverter single lamp, dual-lamp, four lamps, six l
Single lamp, dual-lamp, four lamps, six lights, eight-lamp backlight board pin functions:
Interface: from left to right
(1), ------ 12V power supply
(2) ------- ground
(4), ------- ADJ
(5) ------- NC
First, find the power: VCC, GND, connected. Inverter and then find out the switch and brighter side, ADJ generally relatively easy to find, it is generally connected to a resistor connect transistor, if you can not distinguish casually connected, does not shine and then transferred over to pick, as long as the power supply feet Do reversed, generally will not damage the Inverter. For example:
The Inverter interface of the two lights:
VCC, ----------- (12V)
GND, ----------- (0V)
ON / OFF, ------ (5V)
ADJ, ------------ (2V)
NC, ------------- empty
Four Lamp Inverter interface is also the same, if it is not lit, it will be ON / OFF, the ADJ for debugging, generally does not shine that is two feet then backwards!
5V G60-445DX Inverter:
1 -------------- VCC (5V)
2 -------------- VCC (5V)
3 -------------- empty
4 -------------- GND
5 --------------- GND
6 --------------- empty
8 --------------- ADJ
If it is not lit will 7,8 feet Swap! A 12V Inverter are similar.
IBM laptop T series repair common problem cases
1, T20 the boot screen dark, 90% is gone inverter power supply is broken screen line.
2, R32 If the boot does not recognize optical drive, the majority of Southbridge empty welding.
3, T30 is NIC bad, it is bad NIC chip.
4, A30/31 if boot Huaping also most graphics the BGA empty welding.
5, IBM T20 T21 T22 T23 four machines with low machine has the same common problem, the CPU power supply chips (ADP3421 and ADP3410) perishable change when general for a pair.
IBM T40 T41 T42 three machines, graphics (7500,32 M) Easy Weld, three the appearance, the motherboard can be used interchangeably. The fault phenomenon Huaping but normal external. 2 into the system after a crash or very slow. 3 power does not boot.
7, IBM X31 boot is not self-test, Northbridge next to the NEC filtering capacitor is another slightly larger than a little, it was OK.
8 Lenovo SL300 SL400 SL500 boot dark screen, due to more than the main panel screen line interface an insurance near open circuit and a non-polar capacitor is shorted, can be replaced.
Zhaoyang E370 Lenovo Tin Yat 100 motherboard and other major parts, interchangeable, both the easy Huaping the problem screen wire loose, reseating the paper taped bear resolves, but the high failure rates, the fundamental The solution is to replace a new screen line.
10 Lenovo 125 screen axis is perishable.
11, Lenovo Idea Pad Y430 notebook screen perishable (141WLED), as well as this the battery is also easy to go wrong.
Failure phenomenon: IBM notebook T2X series appear dark screen
Solution: replace the inverter or lamp
Failure phenomenon: IBM notebook the T2X memory slot easily imaginary
Solution: add welding memory slot
Failure phenomenon: IBM notebook the T40/41 machine common problem, blue screen or crash phenomenon Huaping
Solution: graphics plus welding or replace.
Dark screen replacement screen for line, the general T22 screen line love broken, is the the motherboard interface eighth foot and IBM Lenovo ThinkPad SL500 Inverter down the third foot love break.
IBM laptop T40 Huaping graphics problem
The IBM notebook common problem T23 laptop motherboard Northbridge next inductance Weld lead to non-powered CPU.
Power-failure does not boot to do graphics BGA.
A complete inverter constituting
Usually input of the inverter main circuit is a DC voltage, since the photovoltaic power generation system is a mountain square solar generated DC, should contain in the input circuit of the associated filter circuit and EMI circuit. The output circuit also normally include object filtering and EMI circuit, to reduce the influence of the inverter circuit produce a corrugated load generated. The role of the control circuit is to produce a system control pulses to control the power switch tube conduction and shut off, and the HP G60-235DX LCD Screen Inverter OEM circuits together to complete the inverter function. Auxiliary functions of the circuit schematic of the inverter input voltage is converted into a control circuit of the required DC working voltage, typically one or several DC-DC converter circuit. The protection circuit hair to include input (output) output overvoltage and undervoltage protection, overload protection, over-current and short-circuit protection circuit and overheat protection. Moreover, the schematic block diagram of the inverter of the most important is that the inverter main circuit. The conversion circuit inverter main circuit of the inverter power switches and other devices, are generally divided into two categories of isolated and non-isolated. Whole constitute the majority of a complete circuit of the inverter, the actual circuit will be by a variety of electronic components, such as the inverter main circuit is generally composed by the power switching device, the control circuit components, generally by a microprocessor or DSP device to intelligent control inverter.
In the inverter circuit of the photovoltaic system, the majority of main circuit topology is used in three circuit structure, i.e. Dc an AC-DC-AC, in addition, can also use a single-stage structure, namely the DC-AC into two structure DC a DC-AC current market commercial sine wave inverter circuit is more of an AC-DC, DC, an AC three-tier circuit structure, its working principle is first the solar phalanx DC low voltage (such as commonly 12V, 24V, 48V or higher) by the high pre-inverter waveform is a square wave AC, followed by a step-up transformer rectifier filter becomes greater than the the above 110V high-voltage direct current, and then after the third level of the DC-AC inverter 220v or 380V frequency alternating current required for the system, the higher the HP G60-530US Inverter efficiency of this inverter structure can be obtained.
CCFL characteristics and features?
The characteristics of the cathode Designed: backlight driver board (the DC / AC the HP Pavilion DV5-1004nr Inverter, the CCFL the INVERTER) CCFL represents a highly nonlinear load shown in Figure 1. The beginning when the cold light is cooling (in the period of operation time), activate the voltage of the EL is generally three times. Designed in Figure 1, is characterized by the activation voltage of 1600 volts, and the general operation of the average voltage is 500-800 volts. Please note, Designed positive resistance at the outset, and then converted to the negative resistance above 1mA. These characteristics mean that it has a high output impedance (current source), can inhibit the negative load resistance effect and can limit the current in the activation Designed. ROYER converter has a low output impedance, so must be added an additional "no loss (loseless) series resistance, for example: a coupling capacitor.
1) the cathode Designed current voltage function.
2) the equivalent circuit of the CCFL. VFL is Designed in the average voltage under normal operation. Designed impedance (RFL) is a complex function, but at a fixed voltage, can be regarded as a fixed negative resistance. Stray capacitance and interconnect capacitance combine to become the CFL.