LCM simple fault exclusion

Application and fault removing of 1 LCD:

The use of '1'.LCD:

The liquid crystal display special principle, structure, installation must pay attention to:

(1) to prevent too much pressure:

Liquid crystal display device is a liquid crystal box made of two pieces of glass, between them is only 5~10um, and the inner surface of the glass is coated with a layer of orientation layer, easy to damage, therefore, should pay attention to the assembly, use:

The surface of the LCD can not be too much pressure, so as not to damage the orientation layer, if the pressure is too large, or use your hands to the central LCD, to be placed at least 1 hours after the electricity.

The assembly remember to uniform pressure, pressure device edge, no pressure, not even harder.

(2) to prevent the glass breakage:

Because the LCD is made of glass, if lost, impact, will cause the rupture, so in the design must consider the assembly method, assembly of the resistance to vibration and impact resistance.

(3) the protection of pins:

If the pin type LCD, then LCD should be installed in the 2mm from the board or further afield, but can not force is too large, excessive heat, so as not to damage the connection. Joint maximum temperature should not exceed 80 DEG C. Pin shall not be used as detergent, detergent in the sunlight will break down Cl2, after absorbing water and hydrochloric acid corrosion electrode.

The device (4) moisture:

Because LCD is a low voltage, low power, the resistivity of liquid crystal material is very high (up to 1010.Cm and above), so the glass surface conductivity due to damp, caused to influence display. Time will show "crosstalk". Therefore, the design should consider the moistureproof, case sealing, even using a sandwich type conductive rubber strip.

(5) to prevent scratches, pollution:

The liquid crystal display device for plastic surface type polarizer, so assembly, use should avoid scratch hard objects, the absolute.

LCD on the surface of the polarizer has a layer of protective film, so as to avoid scratches, stains. The assembly should be completed at the end of the assembly, the protective film off. Even so, in the installation, operation, better with cotton gloves, to avoid contamination of hands sweat, grease, cosmetics etc.. As has been contaminated, should be promptly with fine cloth, cotton swab treatment such as contamination; heavy solvent cleaning must be used, only with isopropanol (glycerin), alcohol wipe, freon, and fast drying, but never with acetone, aromatic solvent (such as toluene and water scrubbing), or damage the LCD the surface of the polarizer.

(6) to prevent the application of DC current:

The driving voltage of the DC component of the smaller the better, preferably not more than 50mV, long time exerted DC components will make the electrode electrochemical reaction and aging. In the display, the two frequency divider circuit in the oscillation circuit, in order to ensure the symmetrical square wave.

(7) the anti ultraviolet:

Liquid crystal and polarizer are organic compounds under UV light irradiation, will produce photochemical reactions, the degradation of LCD, so should be based on the conditions of use and the environment to consider whether the device anti UV filter.

(8) in the specified temperature range and storage:

Because more than the liquid crystal temperature range will disappear, so it must be used in the specified temperature range and storage. The temperature is too high, the liquid crystal state into liquid disappears, isotropic, display is black, can not work. At this point do not power, until the temperature returned to normal display surface will be back to normal. If the temperature is too low, the liquid crystal will disappear, into a crystal. May destroy the orientation layer during the formation of crystals and cause permanent damage at.

(9) the electrostatic interference:

Because LCD is extremely low operating voltage, resistance, and so on with a multimeter (* 10K) examination, sometimes there will be a "string" phenomenon, this is because the electrode suspended by, is a normal phenomenon.

'2' to rule out the use of fault:

A qualified for display devices, sometimes due to the use of unreasonable, the suitable condition and fittings unqualified or improper installation failure. The following is the reason and solving method:

(1) are excluded:

The use of a few hours or a few days later, black, brown discoloration of the electrode, the liquid crystal box "handwriting" bubble, which can not be displayed. This is because the driving voltage of DC component is too large, resulting in the electrochemical reaction caused by. Check the circuit, ruled out large DC component, a new LCD. When just "writing", the LCD can be heated to the temperature above, stop heating the display device display surface, color, after natural cooling, can get rid of "writing".

(2) can display:

Segment assembly also is not the display can display, so as not to read, the reason may be:

The lead is not clean, dry cloth to wipe.

The weather is too dry, the surface of the glass can be conductive, recovery room after drying.

The common electrode or electrode suspended period, re assembly and reliable, can be eliminated.

The AC square wave on the amplitude asymmetry, caused by not clear off, adjust the square wave amplitude can be solved.

The conductive rubber stripes are not, not parallel, poor insulating performance, conductive rubber can be replaced.

(3) out of contrast:

Contrast is very poor, or negative, or confusing, or all, generally due to suspension caused by the back electrode, can be excluded.

(4) shows the exclusion of chaos:

External interference may also cause confusing, can be excluded.

(5) all showed exclusion:

The decoder normal, but all that is not good, the back electrode, and the back electrode current.

(6) the lack of out of plan display:

The reason may be missing segment display:

The electrode lead contamination, resulting in poor contact assembly.

The conductive rubber contamination, resulting in poor contact assembly.

More than two of only cleaned after the assembly, the assembly can not touch the cleaned parts.

The edge of the glass breakage, scratch wire conductive layer.

The pressure box assembly is unqualified.

(7) shows the exclusion of chaos:

Causes chaos display may be suspended, drive: the back electrode, DC power fluctuation, poor contact, the battery is depleted, according to different causes were excluded.

(8) showed intermittent exclusion:

Function disorder, not adjustable, the reason for the power supply voltage is abnormal, the battery is depleted, the need to replace the battery.

Excluding the 2 module fault:

In order to eliminate the faults, the module must have a certain understanding, so the repair module, can play a multiplier effect.

"1" prerequisite for troubleshooting:

As to the assembled modules, to have some understanding of the principle of module, this module in the assembly problems will have a definite object in view. Such as: when a PCB chip pins on the control panel of two SEG electrodes, once found module symmetry appear to lack of two SEG, can be concluded that the PCB problem.
Want to have certain understanding to module composition. A module, want to have good power display, screen, shell, zebra, PCB plate must be reasonable design, qualified raw materials can have a good effect. Such as: the compression ratio is not enough, resulting in lack of planning, the assembly is not repeated, reliability, then we must change the zebra.

In order to master the assembly of certain skills, master certain skills in troubleshooting, you can handy, reduce the occurrence of assembly problem.

"2" rule out simple fault:

(1) show that chaos exclusion:

1). Dislocation: not PCB plate electrode and the electrode corresponding to the one one screen, then to analyze the causes of dislocation.

At this time because the assembly I techniques in assembly problems caused by the,, re assembly.

The PCB board mounting hole location.

The screen edge cutting accuracy.

The shell counterpoint benchmark made inaccurate.

2).PCB board is bad, then can test plate tooling plate again measures.

External interference may also display confusion lead, then found outside interference, can be excluded.

The lack of rule is displayed:

1) PCB electrode was contaminated, resulting in the poor contact.
2) the contamination, resulting in poor contact.
3) conductive pole was contaminated, resulting in poor contact.
More than 3 of only cleaned after re assembly. When assembled, can not touch the parts after cleaning by hand.
4) PCB plate breakage, weld. And have the test board, for once, such as bad.
5) screen electrode breakage or screen itself, short circuit fault. To screen for re assembly.
6) shell is not qualified, shedding after re assembly.

(3) showed no or all black:
This is generally the PCB board, PCB board to remove after the re measurement.

(4) showed uneven, shallow section.
In this case, he carefully analyzed to be excluded.
A display unevenness, but the connection is not tidy. This is generally the screen, change after re assembly.
Second, a few display unevenness. In this case, the general is the distorted, resulting in poor contact. To be removed after,
The zebra flat, re assembly. If you can not rule out other reasons, it is necessary to analyze, such as zebra, high aspect ratio is not appropriate, the compression ratio is not suitable, not appropriate electrical bandwidth.
PCB board slightly cold solder joint. Remove the PCB board, PCB board, re assembly.

(5) semi deep half light, the program does not go, abnormal program, less of a screen or a few screen, no adjustment, a shadow.
This phenomenon is generally PCB board problem, need to remove the PCB plate PCB plate. PCB board with good re assembly.