Troubleshoot Computer Monitor Problems

Published: 14th July 2010
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Identify whether damaged the power supply

Previous computer monitor used 14-/15-inch LCD PC monitors by using dial to adjust, power switch is the hard-switching. When turn off the monitor power switch. monitor internal power supply is completely cut off. As for the display using CNC technology, its working state controled by the display's internal MCU.When you turn off the monitor power switch, monitor the switching power supply circuit section and the Department of MCU is still in working state. If you do not use display for a long time , it is best to unplug the monitor power plug



1 Damage to the power switch

the power switch of CNC monitor works in the small current state,the rate of damage is very small.When you insert the monitor power plug, if we can hear the slight "crack" sound, indicating the internal monitor switching power supply is normal, while the power fuse intact. If the display of power that does not light, in most cases is not a bad switch, but the power circuit.



2 Fuse damage

If the fuse is damaged, do not easily replace the fuse, and fuse should further identify the causes of damage. Basic judging criteria are as follows:

Glass tube surface is clear and transparent,Only one internal fuse fused.This is due to unexpected electricity surge voltage circuit in the presence or because of frequent switching machine, there may also be the work of the ambient temperature is too low and unexpected fuse.at this time fuse can be replaced directly with the same model.

Note: The display and color TV with the same insurance, rather than the ordinary delay fuse, generally 14,15,17 can be used 3.15A, some 17 5A fuse should be adopted. The fuse for the use of ceramic packages, the best alternative use of the same model in order to avoid frequent replacement of fuse.

Glass tube surface with a yellow and black sputtering dirt,and can see the shape of the internal fuse.This is generally the circuit tube breakdown, due to power PWM control block breakdown

Glass tubes serious burst.This is generally not vulnerable, mostly due to short-circuit power directly. Should be carefully examined before the rectifier circuit, as well as degaussing coil.

or cracking of the surface of glass tubes, difficult to see the internal situation.This is generally a two 220V rectifier diode breakdown, capacitor breakdown caused by short circuit.



3 Damage the power cord.Sometimes because of accident or collision pulling force, internal power supply line may also be broken, then the method of replacement can be used to identify.



4 Plug the power cord and display loose.Sometimes specification is not very standard, and do not consistent with the display of the power outlet very tight, causing poor contact .will result the phenomenon of light is on and off,not working properly. and monitors the power increase is not the same. just like can't connect the power.



Whether abnormal sound

Inherent several normal voice of display: the voice of degaussing circuit magnetization (bang bang, and the degaussing relay synchronization, sound close to the overlap), the internal degaussing relay sound (clicking twice, interval 4S), line circuit relay sound (clicking the once or twice with more force), high-voltage charge voice (the voice creak Lala about 3 seconds).

1,Clear "flap" sound of high-voltage discharge

This is generally due to a high voltage discharge circuit around FBT phenomenon.Return to service. Note: If the display is intermittent or continuous within the "flap" sound of high-voltage discharge, the time should be immediately shut down, or because of high voltage discharge to the breakdown of other components, so that failure extend the tubes caused serious or even scrapped.

2,Relay continuous action "clicking" sound

Note: For numerical display, each time you switch, have a "clicking" sound of the degaussing relay chorus, spaced about 4 seconds, then release.Some also accompanied by S correction circuit relay pull-sound, but this is only at boot time and change the screen mode, it appears.

3,Slight "squeaking" sound

Display a slight internal short circuit, causing power supply overloading caused.Return to service.

Note: Some monitors display panel switch is pressed, the display will be more obvious inside the "creak" sound, because the switching transformer to light loads, self-generated sounds.Some few seconds away, and some may still exist, unless you unplug the monitor power plug. But this is normal.

4,Weak weak "blah" sound

If there is such a sound, sometimes accompanied by power indicator light and dark flashes.This is because the power supply circuit has a serious short circuit.Return to service.

5,Apparent "imperfections" sound

This is not a display switching transformer caused the grounding side loose. Return to service.



Odor judge

1,Sour

If there is such a taste. General internal capacitor overheating or over-voltage burst, the capacitor acid gas spill.

2,Paste flavor

Generally because of the large heat source within the display items such as power tubes, diodes, resistors and other large excess heat caused by burning of the circuit board.

3,Odor

This is generally due to the high-pressure mouth of monitors wet then leakage of the air discharge



Display image is not normal

1,Horizontal line

one or two faint horizontal (approximately 0.2mm width)

For the Sony Trinitron monitors, because of their use of grid-shaped mask plates, in order to prevent deformation of the shadow mask plate added damping line, 15 "for one 17" for two

a few centimeters wide, gray or dark gray bar

If the display appears in the course of a few centimeters wide and deep color interference may be moved up and down and from time to time, when the circuit can be judged is the display part of a Weld-line situation.



2,Vertical line

imperceptible thin vertical line

For the Sony Trinitron monitors, probably because the temperature is too low, mask plate caused a slight deformation, such as this usually disappears when the temperature is normal.

a few centimeters wide, gray or dark gray vertical bar

This is not a field with circuit caused damage or if Weld.

the left thread

Display on the left near the edge of the slightly thin, this is caused because the current production technology, only some display obvious that some not obvious.They are qualified if they do not affect the normal use of both products.

either side of the S-shaped vertical movement of the vertical bar

This usually is due to the power monitor diode rectifier circuits in individual tubes or damage caused by high voltage capacitance decreases.



3,Black spots

1,one or 2-3 small black spots

As the current production technology with no guarantee on every CRT phosphors are completely normal, so there is an individual display or 2-3 small black spots, this is normal.

large black spots

This black spots usually appear in the display center, which is usually because the circuit failure caused by consumption highlights the central position of the phosphor due to premature aging. This situation can not be repaired.

irregular beating of the black spots.This is usually caused by the interference of the internal display.



4,Highlights

small white highlights.With black specks, and is caused because the production process.

Color Highlights.Splashing water droplets or oil droplets due to the CRT surface light scattering. Scrubbing can be removed.

Irregular white block.For the display surface coating is caused due to surface coating to peel.Beyond repair.

Irregular beating of the white spots appear or white line, about 1-2 mm in diameter.This is usually caused by external strong signal interference.However, when the internal circuit failures have this phenomenon.



5,Water ripple

As the current production technology and processes can not completely eliminate the water ripple display (also known as Moore interference), can only decrease.Some customers called the water ripple serious "vortex." Sometimes, like as the wind from one end to the other side of the display. When just opened machine's display, this phenomenon is very obvious, but after half an hour or more, this situation should be reduced or disappear.As long as interference in the allowed range, all is normal.Display a slight edge of water ripple is normal, the more obvious focus more clearly waterlines.We should note that: If you want to display work well should be supplied a standard work environment, otherwise would be a very strange fault.



6,Flicker caused generally due to the refresh rate too low. But if you transferred to 75HZ refresh rate monitor above, the image is still flickering as before, this may be a problem with the internal circuit monitors.



7,Shake

The whole image up and down the whole site at the same time jitter. Poor market performance of the circuit.

About the same time, beat the whole image. Line circuit performance not good.

CRT screen image is only part of the region around chattering.

Image brightness changed significantly, sometimes accompanied by changes in image size.



8,Fuzzy

① Clear beginning, with the use of time, become increasingly blurred.

This is the display line scanning circuit in question may be FBT (Fly Back Transfer) leakage drift, it may be line management, reverse-way diode capacitance reverse process due to poor thermal stability. This failure can only return to service.

② First fuzzy, over 10 minutes or half an hour after the clear and normal.

This is usually caused by damp CRT tube socket. Most of the work environment because the display where the humidity too much, not always monitor the use of seat tube due to increased moisture resistance.Minor fault when the continuous operation of the display of several hours can be resolved.If the failure is serious this time to replace CRT sockets.

③ The CRTtank screen image blurred, illegible text and image detail.

This is generally the focus potentiometer FBT move, or FBT leakage.If the age-old CRT monitor mostly due to the aging of defocusing.If the potentiometer can be adjusted to solve mobile, if the leakage is only through the replacement of FBT FBT.

④ The CRT screen image in one direction as the wind-like tail.

Then you can compare at this time whether the OSD menu is the same phenomenon.If not, this may be faulty graphics card. If so, this is the display of the color processing circuit fault caused.

⑤ CRT screen part of the area with color trim.

This is not a static display good convergence performance. When the display part of the magnetization when there is the phenomenon.The failure need to disassemble to adjust.



9,Deformation

① just opened the screen when there is such a small machine, basically to normal after a few minutes.

This is a display typical "breathing effect" Bale is just too obvious. Display in the work under normal circumstances, the image should not be significantly larger or smaller, if such note display certain elements within the good thermal stability.

② image distortion.

Images distorted by adjusting the OSD menu or adjust the unit does not shut off after the loss of normal, indicating that the display memory circuit or MCU control circuit problem.

③ When the display switch different mode, the image changes significantly, or in 640 * 480 is also Man-screen, but obviously under 800 * 600 screen reduced in 1024 * 768 into a narrow under the section, but the content integrity and image clarity. This is the display's internal B + voltage automatic tracking circuit problems, the general problem is the line scanning block and some features or damage caused by MCU.



10,Splash

Irregular blocks of color on the screen or part of the regional apparent bias in a particular color or Pianan, this is because the display caused by magnetization.If the minor magnetization, degaussing circuit through the display itself (note: do not repeat the degaussing in half an hour.), If the display itself can not be eliminated, you can try degaussing wand will be solved. However, if the display board inside the magnetic shield Meng or deformation, the stain is not removed.



11,Color cast

① If the apparent lack of a color display (R, G, BTANK), this is the problem caused by display signaling pathway.Please check the 15-pin D-shaped plug, see 1,2, 3-pin if they are defective.If there is no signal line is broken or the end of the internal circuit board problem.

② If the display screen is constant R or G or B, and adjust the void, which is very touching because the internal CRT or tail circuit.

③ If significant bias background image a certain color, then you can try to RGB by OSD menu to adjust back to normal.If not, is due to tube aging.





12,Too dark and the display screen at maximum brightness

If the display brightness too dark, but this time adjusting the brightness is 100, then enter the factory mode to adjust the brightness of the deputy.Because the display mode of each of the memory in the display are user data and standard data, when the user to adjust, the display of the MCU must current data and standard data for comparison, in order to prevent causing display circuit protection. If the display changes to the standard data is accidental, then the display appears too dark or too bright situation.



13,Monitor circuit and can not be too bright, dim

If the display brightness is too bright, even if the brightness adjusted to 0, the image is very bright, which is the display brightness control circuit (ABL or ABC circuit) due to loss of control.This failure to disassemble, repair.



14,After the shutdown screen there is a bright spot, about 3-5 seconds and then disappeared

This is because the news highlights display a fault in the circuit, can not effectively prevent the shutdown is still in the high temperature of the cathode to the launch of the electronic screen, because there is no deflection circuit, when the electrons hit the screen to form a diameter of about 3-5 mm spot.If this occurred a long time, will cause premature aging of the screen center of the phosphor, resulting in a marked center of the screen dark spots.This failure to disassemble, repair.



15,Monitor power indicator light, but no images

① just power-charging when the sound pressure, while the power indicator is green, too, after about 5-10 seconds, the indicator light turns orange, and accompanied by loss of high-pressure "creak La La" sound.Then about 15 monitors can be judged is the core of the data lines, line or field sync signal line (13 or 14 gauge needle) has a broken one, so that the display did not mistakenly believe that the host sent the signal, over 4-5 seconds automatically enter low power saving state.

② high voltage charge when power is not the voice, even remove the signal line, power indicator light is always green.This is generally line scanning circuit fault, did not produce high pressure.

③ When a high voltage power-charged voice, no image on the screen, remove the signal line, the power indicator to orange after a while, and accompanied by high-pressure discharge sound.Circuit fault for this situation, CRT is generally not coupled with a certain voltage, then you can look, CRT's filament is not bright.Also possible that the gate voltage is not added.



16,Display the menu settings can not be stored

After each turn needs to adjust the display settings, adjusted to normal use, but data loss after shutdown.This is the display of the memory circuit is faulty, can not save the current settings.When the display memory circuit fails, there are other strange fault phenomena, such as images can not be transferred light (dark), can not transfer full screen, color cast and so on.



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