LCD MONITOR REPAIR GUIDE PDF
TV Repair Tips V LCD TV Repair Tips & Case Histories LCD/LED & 3D TV Recommended Troubleshooting & Repairing Guide: V –LED & LCD TV. This is a copyrighted material; no part of this guide may be reproduced or transmitted in any form whatsoever, electronic, or mechanical, including photocopying. Download LCD MONITOR REPAIR GUIDE service manual & repair info for electronics experts.
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Download LCD MONITOR REPAIR GUIDE JESTINE YONG service manual & repair info for electronics experts. This is a copyrighted material; no part of this guide may be reproduced or transmitted in How to Repair LCD Monitor Power Adapter How to Repair No yazik.info Voltage test. The third. No much lcd monitor repair book or Lcd Monitor Repair Pdf has compiled these questions. 1) how repair lcd monitor with no power problem, 2) how trouble.
It's almost as if a fuse is blown, though if I listen very carefully I can hear the power supply 'ticking' very very softly. I just bought the monitor factory refurbished by HP in , only has about hours on it; I expected it to last much longer than this. Would this be typical of some faulty electrolytic capacitors, or is it likely to be a more serious problem? I don't see anything obvious, no bulging caps, no burnt parts, nothing. The circuit seems to be a standard switching supply, which sends the v power first through a charge pump, which raises the voltage to around v.
It then goes into a switchmode transformer to create 5v, 12v and 24v to run the scaler board and inverter. Upon checking further, the main v bus seems to be at only v, indicating the charge pump is not functioning or starting.
The v in and charge pump diode check ok. For the backlight inverter board with Direct Drives, the main advantages of the pushpull transformer are its dual primary winding construction which the voltage impressed across the primary in Direct Drive modules which are twice the supply voltage. Direct Drive topology also enables efficient inverters that can run directly from 3.
This is equivalent to a 4 transistor full or H-bridge drive configuration and makes for very efficient operation at low voltages. Unlike the implementation of Royer regulator, new approach of Direct Drive for lamp strike voltage generation relieves the transformer from operating continuously at full lamp strike voltage once the lamp is ignited. Direct Drive transformers will optimize for normal operation where they spend most of their life. Small transformers can be used while system a CCFL is only present for the instant it is required.
Gradually destroying the insulation material, high voltage corona discharge can be more easily avoided with Direct Drive designs. With the new transformers and IC controller, the backlight inverter board of Direct Drive has been developed completely which the first two are 6 watt units that can drive lamps having strike voltages of up to Vrms.
A two lamp magnetic now in development will support up to Vrms strike and 12W operating power. Clearly, strike capability is enhanced while transformer size and reliability are improved. In big picture, Direct Drive designs reduce transformer output voltage after ignition, permitting ballast capacitance values to be much larger.
Now you have learned the direct drives backlight inverter board. You will be more familiar with the inverter board when you have chances to open out the LCD monitors casing and observe it yourself.
Inverters must accept the dc input voltages, typically 12V, and provide ac outputs of to V to run the lamps. To ignite CCFL lamps, these circuits must supply short strike voltages that typically are double that of their working voltages. Numerous applications also expect efficient dimming capabilities to let lamp output to match surrounding light conditions and so extend the lifetime of lamp.
It depends on the number of ccfls are used, inverter circuits combine with single, dual or quad high voltage transformer to generate the high voltage required for ccfls. For ccfl inverter voltage generation, the inverter circuit with the buck regulator consists of two power semiconductors, one power inductor, a PWM regulator IC, and a high current capacitor.
LCD MONITOR REPAIR
It provides a healthy secondary power source from the primary power source. The Royer oscillator consists of two transistors, a high-current resonance capacitor, a high-voltage transformer, and a ballast capacitor in series with the lamp. It provides an alternating current source to drive the lamp. The current amplitude is controlled by the ballast capacitor through the lamps negative impedance which dropping an approximately equal voltage across its positive impedance.
In theory, the lamp current will be the total transformer output voltage minus the lamp voltage lamp voltage is inversely proportional to current divided by the capacitors impedance. The total power and the required strike voltage will limit the minimum size of this transformer.
Because it must operate at twice the normal lamp running voltage all the time, its size must support full strike power and voltage, even after the lamp is ignited. Knowing the good ccfl inverter voltage is critical to troubleshooting LCD Monitor. You can use the spare backlight from another working LCD Monitor.
This is important method to test the backlight. Otherwise, you will waste time and money if the fault is on the inverter circuit or dry soldering and etc.
Normally, the backlight fault will be suspected when you found the display is flickering or discoloring. Double check any dark end on cold cathode tube. Replace new tube if you discover the dark end of lamp tube. To replace the backlight successfully, you must pull out the backlight gently together with its casing. Some backlight can be easily removed while some were tough.
For totally sealed type backlight, you must be careful when removing the backlight. Once you tear off the backlights tape automatic bonding accidentally, the panel of LCD monitor is damaged and no longer operate in good condition. Always bear in mind, the tape automatic bonding is very fragile before you pull out the cold cathode tube. Be careful and good luck for your lcd monitor backlight replacement. Here is a typical lcd backlight replacement which the faulty lcd monitor is turning on and off cyclically then off permanently.
You can see brief OSD setup menu image appeared for while and black out. No ccfl replacement is required. You may plug it to another good Lcd monitor to ensure your cpu is in good condition. If the fuse is blown, trace the circuit lines and went to the high voltage part of the PCB. Suspect some parts went wrong over there. Confirm it with Atlas component analyzer to avoid wrong measurement.
Notice the transistor was shifted from its original position. The culprit is the back heatsink Collector has been shorted to the line that connects to the Emitter. Probably, the smd transistor is overheated and melted is the root cause. The adjacent NPN transistor next to it also was a bit shifted. In this section consists of fast switching on and off power semiconductor devices, such as MOSFETs and Bipolar transistors and switch the input voltage across the primary of the power transformer.
The driven pulses are usually 20kHz to kHz with variable duty cycle. In the transformer secondary will generate a voltage pulse train with varying magnitude and duty ratio. Now, you got the idea of the lcd monitor repair with mastering the working principle of lcd monitor circuits.
The indication of the monitor is no power and blank screen even though the external power supply is plugged in. After I have listened to his words, I do a quick test on the monitor in front of him to double-check the problem.
Exactly, the monitor has no led power lit when switch on the power supply. He requests me to repair the monitor as soon as possible because this monitor brings him lots of winning on stock trading. He wishes to use the same setting so that he can win the trade in the stock market.
I reply to him confidently that he will be able to receive his monitor next 2 days or early. Then, he walks away happily.
LCD Monitor Repair
Because, I have similar experience on the same model of the monitor and good understanding of circuit operation especially on the switching mode power supply.
There is a systematical method I will tell you right here on how to analyze and repair LCD monitor no power in simple and quick way. Is the fuse blown?
Immediately, I unscrew the outer and inner covers of LCD monitor. Please ensure no power connected to the monitor. The first place to be checked is on the power supply board. I measure the continuity of the fuse and Both of them are in good resistance.
After that, I inspect all capacitors, resistors, inductors, diodes and ICs are in good shape. For a quick test, I plug in the power cord and switch on the monitor to do the voltage testing.
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I use the voltmeter to measure the 12 Vdc output of the secondary transformer Guess what do I find out?
No DC voltage is measured right here. This means the primary section of transformer is not functioning which there is no pulse is provided by the power IC to the transistor and followed by the rapid switching of the transistor to induce the transformer in normal operating condition.
I guess a high probability fault on primary circuit of power supply board. Download the guide on the theory of the switched mode power supply for your reference.
Now, I will check two important voltage test points on the primary circuit which are the big filtered capacitor and Power IC , pin 1. I got reading Volts on in good condition but the input voltage to IC pin 1 is 6 volts only. In normal operating condition of IC , the input voltage must be at least 11 Volts or above to start up and oscillate itself internally.
Surprisingly, the voltage across the resistors has fallen to half value of 16Vdc. I switch off the power supply immediately and de-solder the resistors and diode from the circuit board. I got the resistance value changed to K ohms each resistors and the diode is ok. According to Ohm law, the resistance that increases will result the voltage drop. I have the spare resistors and replace the resistors in same specification properly. Within my expectation, the LCD monitor now is returned to normal condition.
I leave it run for few hours. Finally, I call the customer to collect the monitor next morning. He receives the monitor happily and gives his appreciation to me. The whole process of the testing and replacement is only taking 1 hour approximately.
I can earn dollar in the short period based on my experience and good knowledge of the working principle on LCD monitors. Now, you can grab this opportunity to learn the systematical method from this book which compiles a step-by-step and headto-toe practical guidance in photos for smps repairing of LCD monitors. You too can become a professional repairer and earn lots of money from this kind of repair.
The answer is always yes with you invest your time and energy to learn the knowledge of basic electronic component testing and learn the working principle of the lcd monitor circuits and stay focus in Lcd monitor repairing. Always remember your safety first.
Lcd Monitor Repair PDF
To become a successful lcd monitor repairer, you must study the knowledge of the electronic component testing and its characteristic such as various type of fuses, resistors, capacitors, inductors, diodes, transistors, integrated circuits and etc. This is a very important step to analyze which electronic components incurred in the lcd monitor fault. The wrong analysis of the electronic component testing will waste your time and energy.
But, prior to testing the electronic components, you must know the basic electronic component coding which is an essential and initial part for the correct interpretation of measurement and testing on Lcd monitor circuits.The reversal of the magnetic field is achieved by reversing the direction of the primary winding current flow. For example S3 is a 4. If the power adapter has many components burned in it then consider getting a new one as the power adapter is beyond economical repair!
The FAN chip seems to be getting only about 0. It provides an alternating current source to drive the lamp.
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