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LCD TV Main Board Power Faults Main Board Power Voltage Faults HandBook For Professional Technicians and Advanced Students

Brought to you by Damon Morrow http://www.PlasmaTVRepairGuide.com LCD TV Repair Secrets Guide LCD TV SMPS Repair 1 NOVACOM

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You cannot give this E-book away for free. You do not have the rights to redistribute this E-book. Copyright@ All Rights Reserved Warning! This is a copyrighted material; no part of this guide may be reproduced or transmitted in any form whatsoever, electronic, or mechanical, including photocopying, printing, recording, or transmitting by any informational storage or retrieval system without expressed written, dated and signed permission from the author. You cannot alter, change, or repackage this document in any manner. Damon reserves the right to use the full force of the law in the protection of his intellectual property including the contents, ideas, and expressions contained herein. Be aware that eBay actively cooperates in closing the account of copyright violators and assisting in the legal pursuit of violations. DISCLAIMER AND/OR LEGAL NOTICES

The reader is expressly warned to consider and adopt all safety precaution that might be indicated by the activities herein and to avoid all potential hazards. This E-book is for informational purposes only and the author do not accept any responsibilities or liabilities resulting from the use of this information. While every attempt has been made to verify the information provided here, the author cannot assume any responsibility for any loss, injury, errors, inaccuracies, omissions or inconvenience sustained by anyone resulting from this information. Most of the tips and secrets given should only be carried out by suitably qualified electronics engineers/technicians. Please be careful as all electrical equipment is potentially dangerous when dismantled. Any perceived slights of policy, specific people or organizations are unintentional.

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Limit of Liability / Disclaimer of Warranty:

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The authors and publisher of this book and the accompanying materials have used their best efforts in preparing this program. The authors and publisher make no representation or warranties with respect to the accuracy, applicability, fitness, or completeness of the contents of this program. They disclaim any warranties (expressed or implied), merchantability, or fitness for any particular purpose. The reader is expressly warned to consider and adapt all safety precautions that might be indicated by the activities here in and to avoid all potential hazards. By following the instructions contained herein, the reader willingly assumes all risks in connection with such instructions. The authors and publisher shall in no event be held liable for any loss or other damages, including but not limited to special, incidental, consequential, or other damages. As always, the advice of a competent legal, tax, accounting or other professional should be sought. This manual contains material protected under International and Federal Copyright Laws and Treaties. No parts of this manual shall be reproduced or transmitted by any means, electronic, mechanical, photocopying, printing and recording or otherwise. Any unauthorized use of this material is prohibited. All product illustration, product names and logo are trademark of their respective manufacturers.

Dedication

This Ebook is dedicated to: Jestine Yong, Sunny, David Maltz, Teonna Flags, Michael Danish, Mr Lyndon and Mr A. Morrow (my Dad) . I would like to give special thanks to Jestine for being a great teacher to me and a great friend and always inspiring me to study harder to become an Engineer of electronics. Also special thanks to David for being my big brother and keeping my spirits up and always encouraging me to stay fit and healthy and to go further and to never give up. Thank you 

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Content 1 Quick Notes

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2 Introduction

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3 Main Board Basics

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4 Main Board Systematic Voltage 4.1-Why is 3.3V and 5V Systematic Voltage Important?

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5 LDO Regulators

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5.1- What Does Low Dropout Voltage Mean? 5.2- Basic LDO Schematic 5.3- LDO Load regulation (Main Digital Board)

6 Buck Converter IC's 6.1- Pulse Width Modulation 6.2- Discontinuous Mode & Continuous Mode 6.3- What Does Freewheel Mean? 6.4- Basic Cascade and Freewheel Components

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7 DDR Termination IC 7.1- What is DDR Termination? 7.2- DDR Basic Pin Definitions

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8 Conclusion

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9 Circuit Glossary Of Terms 10 Recommended Resources

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Quick Notes

LCD TV Main Board Secrets and LCD Main Board Power Voltage Faults For Professional Technicians Or Advanced Technicians

In this handbook we will cover a few random secrets concerning voltage supply faults on LCD TV main-boards. The faults covered in this handbook are related to supplying the proper voltage to various areas of the main-board. This handbook assumes the SMPS board is functioning properly and voltage supply errors are rooting from the power section of the main-board. This handbook will also cover main-board System Voltages, specifically 3.3V and 5V rails and different design methods engineers use when implementing a new main-board portfolio. This includes bad designs proven to fail and improvements made to guarantee better circuit performance. There are 3 IC chips with-in the main-boards power sections that are known to develop internal errors causing the main-board to default into systematic shutdown. We will cover these 3 IC chips and how they all work together in maintaining and supplying proper voltages, system voltages, and how they have failed with-in the main-board. The fault symptoms these 3 chips cause along with errors in system voltages are as follows: TV will not come out of Stand-By mode System Voltage/Op-Amps & LDO's TV turns on then shuts down Buck converter IC's TV intermittently shuts its self down DDR Termination Regulator IC This handbook assumes that the reader(s) are professional electronics technicians who have full knowledge of circuit fundamentals and a solid education in using various test equipment. This handbook does not teach about electronic circuits or how to use test equipment. This handbook is intended for experienced professional TV technicians looking to service a few voltage supply problems with-in LCD TV main-boards. Information in these pages are general and does not pertain to a specific model of LCD TV but rather a fair range of LCD TV main-board design revisions manufactured between 2005-2011. Keep in mind this handbook is about main-board internal power faults, and assumes the LCD TV power board (SMPS) is functioning properly.

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Introduction

This handbook briefly covers three, 8-pin IC chips on LCD TV main-boards which fail quite often and will require a digital oscilloscope and a good DV meter to troubleshoot properly. Servicing main-boards simply involve using digital scopes, good soldering and desoldering skills to remove and replace fine pitched SMD IC's and SMD components. Different technicians have various levels of electronics education and servicing experience, some technicians service LCD TV's at component level while other technicians service LCD TV's by replacing boards (board-level-tech). Servicing LCD TV's at component level is always the most profitable way to repair LCD TV's but many times technicians have difficulty in replacing small SMD parts on main-boards. Removing and replacing SMD components on main-boards simply require some practice, some technicians use cellular phone circuitry to perfect there SMD soldering and desoldering skills. Other technicians use old main-boards (no longer in use) to gain better SMD soldering techniques. In some servicing cases technicians sometime have a hard time finding the IC they need or they are required to purchase 100+ IC's from a particular parts vendor, and this is the down side to component level repair. The IC chips covered in these pages are usually available from multiple IC chip vendors. Some technicians gather a group of various main-boards and strip off the IC's in which they will use for other main-board repair. There are IC's such as HexFet chips (and others) in which a technician can remove from a plasma TV main-board and use it to replace a HexFet on an LCD TV main-board. Any TV technician who has many expendable main-boards piled up should strip off all the 8pin converter/buck IC's and switching IC's which fail often and are interchangeable between plasma TV main-boards and LCD TV main-boards. Other IC's such as EEPROMS, Flash-ROM's, Expander IC's (and others) are application specific and are not interchangeable. There are many online video's which demonstrate how to remove and replace SMD/BGA IC chips and SMD fine pitched components, I would highly encourage this interactive method of learning different soldering and desoldering techniques of SMD components and BGA/PGA IC's. This handbook simply points out what area the of the main-board the technician should start troubleshooting, in relation to supply voltage faults with-in the main-boards power supply section. This handbook assumes the reader has all proper soldering and desoldering skills and techniques to remove and replace components and IC chip semiconductors on main-boards properly.

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So without any further due lets get started 6 NOVACOM

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Main Board Basics

Fig1A illustrates a basic layout of an LCD TV main board, Fig2A illustrates the category of IC chip semiconductors mounted on a typical LCD TV main board. Fig3A illustrates the basic SMD components, caps, connectors etc, just to keep familiar with a typical main board setup. However Fig4A will be the area of focus in this handbook, which is the power supply section of the main board.

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Main Board Systematic Voltage

Before we cover the 3 IC's known for causing main-board voltage problems lets first cover a very popular problem with main-boards which are System Voltages with-in the main-boards systematic voltage network. These voltages are 3.3V and 5V and are also shared by the T-con board as well as the main-boards central core processor and detection/feedback circuitry. Before we get into the problems these voltages cause when they change or drop in their regulated value lets first understand what they are, and why engineers have used them (including design tricks) and what industry changes and improvements have already been implemented since 2010. 4.1) Why is 3.3V and 5V Systematic Voltage Important? Core processor chip sets (microcontrollers) and logic families on LCD TV main-boards that operate from 3.3V supplies (verses 5V supply) are receiving wide range acceptance in LCD TV main-board design and implementation protocol. In the LCD TV engineering industry there’s an ever increasing need and desire for faster processing speeds. Because of this need and desire for faster processing speeds there is naturally an on going reduction in the physical size of the transistors used in the construction of modern microcontrollers (core processors). Up scaling modern integration along with reduced costs also fuels the need for smaller geometries (design algorithms). But, with reduced physical size of the embedded transistors will result in a decline of the transistors breakdown voltage. When the breakdown voltage drops below the supply voltage, this drop will reciprocally affect the supply voltage as well, causing it to drop. The bottom line here is that processor speeds for LCD TV main boards are ever increasing so the complexity is building up, so consequently its inevitable that main board supply voltages drop from 5V to 3.3V and in some high density configurations the supply voltage can drop to 1.7V as well. The problem with many main boards are engineers trying to implement and interface 5V and 3.3V systems together (called a sub-system), and as a result it causes breakdown voltage problems. This is when the LCD TV will turn fully on then shut right back down again (STB) or will not turn fully on at all. There are many microcontroller manufacturers who make core processors for LCD TV video production who have achieved an adequate level of speed and complexity and now these manufactures are also transitioning to sub-5V voltage supplies for modern LCD TV main boards.

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In fact, there are so many logical reasons for microcontroller engineers to implement 3.3V systems with such fine geometries that 5V is simply not allowed anymore in imbedded digital systems for LCD TV main boards. Soon all TV technicians will no longer see any 5V rails or 5V-Stand-By in newer LCD TV main board systematic voltages (especially LED LCD TV's). The introduction of the new 3.3V or 3V standard used as a supply voltage has been widely used in various design activities for digital systematic voltages on LCD TV main boards. But often, there’s a incremental transition from 5V to 3.3V or 3V sub-systems simply because sometime there are components required that are not available to adopt in a particular design protocol. Another reason for gradual transition from 5V to 3.3V or 3V is that a system can be so complex that 3.3V or 3V is only introduced as part of the digital system. The headache in which LCD TV engineers face is that most (if not all) the interface circuitry is still configured for 5V supply voltages. So now main board engineers are faced with the excruciating task of interfacing 3.3V and 5V systems which also include the translation of logic levels along with powering the 3.3V systems then translating analog signals all across the 3.3V and 5V hurdle (barrier). Next page in Fig B1 are just a couple of schematic examples of how main board engineers try to tackle a reliable 3.3V output from a 5V input source or reference voltage using a simple Op-Amp or Low Voltage Dropout Regulator (LDO) configured as a Comp-Translator circuit (basic design trick). This example circuit is usually found near the SMPS input area (power supply section) of the main board, where the SMPS delivers the 5V to the main boards input (5V input to Op-Amp and steady 3.3V output). But first, lets quickly refresh on what a basic voltage regulator is in Fig 5A. Voltage regulators (Op-Amps) simply convert an applied input voltage to a fixed (regulated) or variable (adjustable) voltage output source. Generally a regulated Reference Voltage is connected to the non-inverting input of the voltage regulator (Op-Amp). The reference voltage is then amplified according to the ratio of the feedback loop and the input resistors, which is the gain. If either one of the resistors (R1/R2) are a potentiometer the output of the Op-Amp (V-out) can be adjusted from Vref to +voltage which is the OpAmps supply voltage. Usually IC chip regulators will have extra transistors to offer a voltage reference and also permits the regulator IC the ability to drive high power loads in which a single OpAmp cannot do alone. Also in Fig 5A is a basic example of the inverting and noninverting Op-amp, where the polarity of the input voltage is applied to the inverting

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input of the Op-Amp and is then reversed at the Op-Amps regulated output source. The inverting input is negative as the non-inverting input is positive.

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FigB1 Illustrates known (and tricky) Op-Amp comparator configurations on LCD TV main boards.

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LDO Regulators

Below in Fig6A is a basic illustration of regulators found on many LCD TV main boards.

5.1 What Does Low Dropout Voltage Mean? The voltage dropout is the I/O differential voltage in which the circuit stops regulating in order to oppose any additional declines with-in the input voltage. That action happens when the input voltage moves toward the output voltage. Fig7A (example A) illustrates a basic schematic of an LDO regulator circuit. As observed in the dropout region the filter element is a resistor (pass resistor 'R') and the value of the voltage dropout is calculated according to its on-resistance (Ron). Example B in Fig7A illustrates the I/O of a typical 3.3V LDO regulator. This LDO's dropout voltage is 350 mV @1000mA and typically this regulator starts dropping out at an input of 3.60V so approximately the span of the dropout region (at the input) is between 2V and 3.60. Any further decline in the dropout voltage will cause the LDO to not function. A common problem with many LDO's on main boards is the ability to stay with-in its dropout region without further decline, and its important to check the value of the SMD 'pass-resistor' before or after testing an LDO, especially for LCD TV main boards that are 5+ years old (2008-2013). In order to maximize regulator efficiency, low dropout voltage is necessary and critical.

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5.2 Basic LDO Schematic

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5.3 LDO Load regulation (Main Digital Board) LDO Load regulation in Fig8A is a measurement of the circuits capability to keep the intended output voltage while it is under load conditions that vary quite often on LCD TV main boards. LDO load regulation faults on main boards sometime occur when the transition of load current fluctuates between 0 and its maximum rated value (0-200mA) and vise-versa at an improper timing scale (mS) which can result in an unintended output indicating an LDO internal fault, this can keep the main board in stand-by mode (healthy timing is around 80mS-120mS). When most professional technicians suspect an LDO load regulation problem on the main board, its known to just replace the LDO to save troubleshooting time. LDO output errors on main boards can cause the TV to stay stuck in stand-by mode because of erroneous LDO output voltage (assuming other fault possibilities have been ruled out such as Power-Good and PS-On logic commands). Check the input to the LDO as well, because sometimes the LDO's output fault can be due to erroneous input variations. Input LDO faults do happen but is rare because when most high-end LDO's are made they are tested for Power Supply Rejection Ratio (PSRR). PSRR (also called Ripple Rejection) is the LDO's ability to stop the regulated output voltage changing caused by faulty input variations. This is why almost all LDO output voltage error's are caused from an internal failure with-in the LDO its self. Be sure to check all SMD and through-hole capacitors (including bypass caps) tied to the LDO for low ESR because they create the control-loop for the LDO and are a paramount factor in supply rejection (this is in relation to faulty input variations too the LDO). Intermittent LDO's (rare) have caused LCD TV main boards to skip from full-on, to immediate full-off, then pull up into stand-by mode again. This type of intermittent LDO main board fault symptom can be almost identical to DDR Termination failures. Since this can be tricky and time consuming to diagnose, most technicians start by replacing the DDR Termination IC (especially if its only 8 pins) which may be suspected, often located around the main boards power supply area. It is more likely this kind of intermittent fault symptom is due to DDR Termination failure, because an intermittent LDO output is a rare discovery in this trade at component level. Many LCD TV main boards manufactured from 2008 use linear LDO's but more modern designs (2012+) now incorporate switching regulators because they are more energy efficient which sharply reduces thermal conditions and don't require external capacitors (for rejection, bypassing, loop control). Keep in mind that even new LDO's are still linear regulators (and still inefficient in comparison) but some of the new LDO design

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schemes give engineers a much broader range of voltage drop input options. This why technicians will still discover a few LDO's on more recent models of LCD TV main boards (even on higher-end main board chassis).

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Buck Converter IC's Switching Regulators

Now lets take a look at those three IC's known for causing power sustain problems on many LCD TV main boards in Fig9A. We are going to look at two IC's first (U1 & U2) because they are basically the same internally and have a much higher failure rate than U3. After which then we will cover the DDR Termination IC (U3). U1 is a 20V 3A Buck Converter IC with internal PWM control function. U2 is a 20V 2A Step-Down Converter IC also with PWM control.

U1 & U2 both have a diode and inductor tied at the output which is critical.

Now lets gain a basic understanding of what a buck converter is by comparing it to a boost converter. Buck means to step-down an input source to a lower output supply and this is why U1 and U2 are basically the same IC's, and boost means to step-up an input source to higher output supply. Buck converters (step-down) begin their voltage conversion using a switch (p-mosfet) in the open-state so this way current cannot get through to any section of the circuit. When the switch is in its closed-state, current begins flowing through the inductor, the inductor then pulls current through the diode. At the inductors output is where the voltage is now lowered. Boost converters begin their voltage conversion with a switch in the closed-state as current starts flowing through the inductor which forces the current to only go through a diode serving as a one-way valve. To quickly slow the current down,

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the voltage is increased higher at the output diode and switch. Voltage keeps the diode open (forward biased) so current can’t flow back. This is why inductors and diodes are so critical at the output of both buck and boost converters, in fact they’re the first two components tested (along with the output filter capacitor) when there's an output problem from a buck or boost IC. The absence of the diode and inductor would mean current has only one path to the output pin and that's directly out-of the input pin, the energy loss would dissipate as heat (linear based) and would contradict the purpose in using a buck switching regulator. Also there are IC's called Buck-Boost converters which is a single semiconductor IC that steps-up and steps-down current/voltage. Main board engineers use this IC when they need the circuit to switch DC voltage configurations above and below the voltage needed to drive the load. However the two IC's in this handbook (U1 & U2) are both step-down (Buck) converter IC chips, U1 has a 3A output and U2 has a 2A output. U1 and U2 are configured as a cascade circuit used for producing a constant low output voltage from the input of the SMPS which varies over a large range depending on current draw. The output voltage is maintained constant by varying the duty-cycle (PWM) of the switching transistor (switch is internal to the buck IC) and the duty-cycle is in accordance with the feedback loop 6.1 Pulse Width Modulation (PWM) (PWM) is an important part of buck converters, it is an internal function with-in the buck IC. PWM uses an internal switching circuit (with-in the buck IC) to rapidly turn the current on and off. PWM does not increase or decrease the voltage, but the voltage average can be lowered. PWM is applied with-in inductive voltage converter IC's (buck or boost) because the output voltage is regulated by varying the duty cycle of a PWM signal which is driving the input to the circuit (load). Only a buck or boost converter can increase or decrease the maximum voltage/current, PWM can only function to lower the average voltage/current from that momentary level. In Fig 10A next page is a basic buck step-down converter circuit, and with this particular circuit when the transistor turns ON it will put the voltage Vin at one end of the inductor. This voltage will cause the inductor current to rise. When the transistor is turned OFF the current continues to flow through the inductor except now flowing through the diode. The current flowing through the inductor doesn't reach zero and the voltage at Vx (V-average) is now only the voltage across the conducting diode during Full OFF time.

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The average voltage along Vx will depend on the average ON time of the transistor, assuming the inductor is continuous. For a steady-state function the current at the start and end of a period T won’t change, assuming there's no voltage drop across the transistor or the diode while ON, and is a perfect switch change. 6.2 Discontinuous Mode & Continuous Mode Buck converters (and boost) function in either continuous mode or discontinuous mode. In the discontinuous mode, converters totally de-energize the output inductor before the end of each switching cycle. There is no current present in the output inductor at the beginning of each switching cycle in the discontinuous mode. In the continuous mode, converters don't fully de-energize the output inductor before the end of each switching cycle. So, the current inside the inductor never gets to a point where there's absolutely no current in the conductor while in continuous mode.

Keep in mind that a buck converter is one type of switching voltage regulator, and there are a few types of switching voltage regulators such as forward and fly-back converters (among others). These different types of converters contain different properties for various applications projects. As was mentioned in earlier pages linear voltage regulators

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(not as efficient as switching regulators) use voltage drops across transistors to convert a higher voltage into a lower voltage.

Buck IC's U1 & U2 in Cascade Configuration Many buck converters on main boards are arranged to feed each other (cascade) in order to efficiently regulate and drive one or more loads over a constant change of voltage/current conditions. LCD TV engineers use buck cascade design because the topology permits multiple regulated voltage outputs using a minimum number of switching devices on the board, and avoids cross regulation difficulties as well. A cascade buck converter configuration on LCD TV main boards comprise of a mainbuck converter (U1) and secondary buck converter (U2). U1 and U2 are coupled by a cascade transistor (SMD) which is in series with a protective switching device called a freewheeling diode or synchronous transistor (all SMD). Fig 11A in the next page illustrates an example of where these components are placed. 6.3 What Does Freewheel Mean? Most main board designers use a freewheeling diode as a protection device because it blocks conduction in one direction and appears as a near short in the opposite direction as the polarity alternates. In modern design schemes on main boards the freewheeling diode is used when the load is inductive and the supply or control voltage is DC, keep in mind buck converters (and boost) use inductive loads at the output. The freewheeling diode(s) are put in the circuit to protect the switching devices (cascade Q1 and Q2) from being damaged by a reverse current from an inductive load. So the freewheeling diode(s) are commonly placed into the circuit so it does not conduct when current is being supplied to an inductive load. When an inductor has current coming too it that is abruptly interrupted the inductor reverses the polarity and increases the voltage level as the inductor tries to maintain its current flow. If there's no freewheeling diode in place the voltage can increase high enough to permanently damage the switching cascade transistors. By having the freewheeling diode in place the reverse current is permitted to conduct through the diode and dissipate. The term 'Freewheeling' may have been derived from the notion that current its self is 'freewheeling' for a brief moment inside the inductor or diode circuit after the voltage supply is switched off.

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Engineers using cascade topology on main boards is yet another well known technique adopted in modern digital board design for LCD TV products. As mentioned in earlier pages newer main board systems require more than just one operating systematic voltage control. The new generation of IC chips requires multiple power supply voltages that are less than 5V of DC. The core processor IC's and logic gate IC's on main boards commonly require voltage sources such as 5V, 3.3V, 2.9V and 1.5V DC. So engineers use cascade topology with switching devices (buck or boost converters) as a solution in providing multiple, well regulated low output voltages in a low cost package which also reduces component count and production cost.

6.4 Basic Cascade and Freewheel Components

Before we start listing known main board power-control problems these two buck converters (U1/U2) cause on main boards lets quickly go over the three switching-mode topologies commonly used. The three topologies are Buck, Boost, and Buck-Boost, these three topologies are non-isolated, which means the input and output voltages share a common ground connection, however there are isolated derivations of these nonisolated topologies, and each topology has its own unique properties such as frequency

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response of duty cycle, and output ripple. A buck-boost converter is a well known nonisolated inverting power stage topology sometimes use on LCD TV main boards. Engineers sometime use a buck-boost power stage because the voltage output is inverted from the voltage input at which the voltage output can be higher (boost power stage) or lower (buck power stage) in magnitude than the voltage input (output polarity is opposite of input polarity). Buck-Boost power stage can operate in continuous or discontinuous inductor current mode. Continuous inductor current mode means the current is continuously flowing in the inductor during the entire switching cycle in steady-state function. Discontinuous inductor current mode means the inductor current is at zero during each and every switching cycle. So, it starts at zero reaches a peak value and returns to zero again during each switching cycle. Let’s start on U1 & U2 Faults.

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U1/U2 Internals & Schematic Example U1: Fig 12A, 13A, / U2: 14A, 15A

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Notice internal P-channel MOSFET switch at pin 4,5,6, in Fig12A/14A

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As illustrated in Fig12A (U1) and Fig14A (U2) both IC's have the same internal function and setup. U1 may have an added feature compared to U2 (not shown in the illustration) such as Soft-Start because it is in direct line-regulation with the SMPS and since both U1 and U2 have dual output ports, one of U1's outputs can be used for noiseisolation. Notice Fig13A and Fig15A are the same except at the output, where the output inductor at U1 is 22uH, and U2 output inductor is 33uH. The following are simply faults that have been recorded from in-house shop records of U1's fault failures on LCD TV main boards flowed by U2 recorded failures. After which we will list faults found with U3 DDR terminator IC. Any internal faults with these buck IC's require replacing the chips as well as replacing any damaged SMD components tied to their pins.

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General Functional Scheme Of U1 and U2 Buck Converters Both buck converters U1 and U2 consist of a step-down switching regulator that has PWM control. Both buck converters also include a reference voltage source, Oscillation circuit, error amplifier, and internal P-channel Mosfet (PMOS). Both buck IC's provide low ripple power, good efficiency and stellar transient characteristics. The internal PWM control control function can be capable of varying the duty ratio (in a linear style) from 0 up to 100%. Both buck converters also contain an error-amplifier, an enable function, an over-current protection function, a short circuit protection function which are built inside both buck IC's. So when over-current protection (OCP) or short-circuit protection (SCP) occurs the operation frequency of both IC's will drop from approximately 300KHz down to approximately 30KHz. Both buck IC's also have an internal compensation block (not shown) to help design engineers reduce component count on the main board. Again U1 may also have an added feature called Soft-Start which is an internal function that prevents overshoot at start-up cycles.

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Main Board U1: No Power/Shutdown 26 NOVACOM

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Main Board U2: Momentary Power/Shutdown The following assume that U1and previous cascade switches Q1/Q2 are in working order.

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Main Board U2: Momentary Power/Shutdown The following assume that U1and previous cascade switches Q1/Q2 are in working order.

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Buck IC Conclusion In general a power-control converter uses semiconductor components to transform power from one form (AC-DC) into another form (DC-DC). This is accomplished by causing the circuit topology to alter by means of turning ON and OFF the semiconductor components or devices. The two 8-pin buck converter IC's we have covered in this handbook are a specific type of DC-DC power control buck converters in-which their design intention is to efficiently step-down DC voltage to a lower level with good stability output and very low output ripple. Some practical main board applications have been illustrated in basic form along with their fault symptoms and failures according to shop records. Sometimes buck IC's are referred to as Chopper Chips throughout the professional TV servicing industry. Buck IC's usually interface between the varying voltage output of a DC load and a sensitive IC such as a Static-RAM IC or microcontroller/processor IC. The two buck IC's (U1/U2) use Feedback control to regulate the voltage output in the presence of varying load changes and feedback influences PWM output duty-cycle of U1/U2. Most professional TV technicians will change both buck IC's, even if only one has an internal fault, because replacing both chips assures no residual damage from another connected buck IC (a known precautionary measure).

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7)

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DDR Termination IC Bus Signal Terminator

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7.1 What is DDR Termination? Before we briefly cover what basic DDR termination is and how U3 fails in three lets take a brief look at how U1, U2, and U3 work together in a basic functional scheme in Fig28A. U1 and U2 are situated in a cascade configuration as the SMPS supplies 12VDC to U1 on the main board. U1 output is stepped down to 5VDC which is switched by Q1/Q2 cascade transistors to the input of U2. U2 takes the switched 5VDC and steps it down to 3.3VDC output. The 3.3V output from U2 is supplied to PVin (pin 7) of U3, PVin powers the DDR IC providing the rail voltage from where the VTT voltage (pin 8) draws its load current (shunt circuitry). The VTT output of U3 is supplied to the termination resistors (signal dissipation) which are directly tied to the data lines (it is vital that no noise gets on the data-lines) of DDR-SDRAM IC. Avin (pin 6) of U3 is voltage control input for the U3's analog (linear) circuitry.

DDR Termination:

Now that we know the basic voltage relationship of U1, U2, and U3 lets cover what DDR is (Peripheral control circuitry for U3 has been left out to keep learning simple). One of the most important functions of an LCD TV main board (aside from power sustain) is its ability to store extremely large quantities of data inside random access memory (RAM) and RAM stores critical and vital memory-data that can be accessed directly and quickly (nS) by the core processor IC. Considering the ever increased need for higher speeds in newer LCD TV digital circuitry, having a basic intuitive

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understanding of DDR Termination is paramount to all professional TV technicians. LCD TV engineers are constantly pushing the design envelope to meet the demand of larger screen LCD TV's with higher picture quality and loads of super data processing at super high speeds. Main board engineers and LCD TV manufacturers have been answering these demands with major breakthroughs and exponential improvements in processor speeds. So with improved processor speeds, SDRAM memory has also made major improvements and breakthroughs to stay current with the design requirements of super processing speeds and demand of the industry. Traditional SDRAM has now developed and evolved into super high-speed chip-sets known as DDR Synchronous Dynamic RAM (SDRAM) chips. DDR-SDRAM is pretty much the same as conventional SDRAM only now double the data-speed (Double Data Rate) and DDR uses Stub-Series Terminated Logic (SSTL) to drive DDR memory accurately. The processing rate is doubled by performing a data fetch on both risingedge and falling-edge of the clock cycle, data-termination is performed after the datafetch which we will cover shortly. Doubling the data rate is a big improvement over traditional single-data-rate (SDR) SDRAM that will perform a data fetch on just one edge of the clock cycle. In this handbook we use traditional DDR also known as DDR1 which has a maximum clock rate of 400MHz and a data-bus of approximately 64 bits and is adopted on older LCD TV main boards (2004-2009) and are still used on millions of modern Low-End LCD TV's (32in-37in). This handbook uses DDR1 to keep the learning curve of DDR bus termination fairly easy to grasp. High-End LCD TV Manufacturers are using DDR2/DDR3 which are basically the same protocol as DDR1 but with higher data rates (800MHz) and some improvements such as On-Die Termination (ODT) which means the DDR2/3-SDRAM IC has built-in data (bus) termination which eliminates the need for external bus termination IC's such as U3 while reducing component count. DDR1 uses 3.3V or 2.5 for core voltages as with DDR2/3 use 1.5V and 1.8V standards for core voltages and trade rumors stating that DDR4 (2014) core voltages will be 1.2V 1.05V (lower core voltage reduces chip thermal peaks). Internal ODT in a DDR2/3SDRAM chip is the primary reason why DDR1-SDRAM topology are physically incompatible with DDR2/3 topologies, however the memory fetching and data termination protocols are similar i.e. ODT.

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Data Termination is routing and ending a data-bus request after a fetch operand by the core processor. When RAM data is requested from the core processor (pre-fetch data) the memory chain has to have an END-point after the data is fetched by the core. The end-of-chain memory is where the pre-fetch data is terminated through SMD resistors (along with bypass capacitors), and the termination voltage (VTT) from U3 is responsible for supplying data termination voltage rail, the VTT voltage output is 1.25V. Memory-data must be terminated in order to avoid an unwanted phenomenon called signal reverberations and reflections which will disturb and interfere with critical memory cells and cause the main board of an LCD TV to shutdown intermittently (dataskipping), or can keep the core processor in reset-mode (will not boot-up). To get deeper into DDR memory termination would be far outside the scope of this handbook. Now lets look into U3 DDR Termination IC and how it fails, firstly there is a lot to gain in how DDR topology works, however troubleshooting a DDR termination IC (U3) is fairly quick and simple. Many 8-pin DDR's simply develop a short (VTT or PVin to GND) mainly because DDR's have an internal op-amp and two or more MOSFET switches. However, there are a couple of other erroneous output faults that DDR termination IC's develop and cause the same symptom of main board intermittent shutdown (and sometimes no boot-up). Now lets quickly examine the pins on U3 (next page) that are vital to its operation and the faults that have developed according to shop records.

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U3 DDR Basic Pin Definitions

Avin, PVin (6, 7,) These two pins have the capability to function from separate power supplies (see Fig28A) depending on if the application is series-termination or parallel-termination. Increased voltages on the PVin pin will boost the maximum continuous output current due to output limitations at voltages adjacent to VTT. Some main board manufacturers tie both PVin and Avin together usually at 2.5V, this method cancels the need for board designers to bypass the two pins separately requiring additional circuitry. Some Lowerend LCD TV manufacturers don’t tie in the PVin rail to voltages that are equal to or less than 3.3V and this is bad because it promotes thermal limit tripping (thermal board shutdown).

VDDQ (5) At this pin the VDDQ voltage is connected to dual internal resistor dividers, the central tap of the resistor divider (VDDQ/2) is connected to the internal voltage buffer in which its output is connected to Vref pin and the non-inverting input of the internal error amplifier as the reference voltage.

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V-SENSE (3) This pin is normally used for enhanced load regulation-control but not all board manufacturers use this pin, however V-sense must still be tied to VTT. A long bus trace will cause a critical drop in current-reference (IR) which causes a major imbalance with the termination voltage (VTT) being weak at one end of the bus than the other. So Vsense is tapped into the center of the bus trace this enhances DDR function because tapping V-sense into the center of the bus trace broadens distribution of the termination bus signal. The V-sense line is very prone to high frequency noise pick-up if its placed in close proximity (physically) to the memory module.

Vref (4) The Vref pin is used to produce a buffered output of the internal reference voltage equivalent to half VDDQ. The two internal resistors (50K ohm) are dividing down the VDDQ voltage on the pin to generate the regulated output voltage. Keep in mind that Vref output has to remain active during a current-limit shutdown state and thermal shutdown condition because a voltage reference is required in order for the 'Suspend-To RAM' (STR) function to work.

VTT (8) This pin is the termination voltage rail (+/-) for the end-of-chain memory and this VTT voltage is dissipated through its connected termination resistors tied to the data lines (pins) of the DDR-SDRAM. Pin 8 of U3 also sinks and sources current output. This is a must, because DDR memory has a push-pull output buffer and the input receiver is a differential stage needing a reference bias mid-point called voltage-reference (Vref). So this means it requires an input voltage termination capable of sourcing and sinking the current.

Thermal Shutdown (2)

(When thermal-shutdown is active VTT will tri-state)

U3 will naturally develop its own heat dissipation due to its internal functionality, if thermal conditions rise above the thermal junction temperature point (threshold limit) thermal-shutdown protection will be triggered and engaged. This happens due to a shorted component, internal fault with U3, or poor circuit design promoting high thermal conditions. In the case of poor circuit design some technicians place a cooling pad on U3 and this returns U3 below the hysteretic trigger point and it resumes normal operation.

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Main Board U3: Intermittent Shutdown/No Boot-up The following assume that U1 and U2 are in working order

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As stated in previous pages DDR topology is complex in how it functions however, testing the DDR termination IC (U3) is fairly quick and simple using a digital oscilloscope and DV meter. In fact some professional TV technicians don't bother testing the DDR IC they just replace it (not recommended for intermediate tech's) because professionals have enough experience to know the symptoms DDR termination IC causes. LDO's, Buck IC's, and DDR IC's commonly pose major problems on LCD TV main boards and until now have been a powerful and affective in-house troubleshooting secret among master technicians for years. The information in this handbook assume that PS-On and Power-Good logic commands are in working order, and to learn more about these important logic commands they are explained in great detail in LCD TV Repair Secrets book and LCD TV SMPS IC Chip Faults book.

Conclusion This manual is dedicated to the greatest technicians David Maltz, Jestine Yong, Sunny, Teonna Flags and Micheal B Danish. For any questions or concerns with LCD TV SMPS repair you can email me at [email protected] All material and illustrations in this manual are original, written, compiled, and illustrated by Damon Diode at TechSociety in USA. To your success,

Damon C Morrow Author of “LCD TV Main Board Secrets”

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Circuit Glossary Of Terms ADC: Analog to Digital Converter. A semiconductor which converts an analog signal into a digital value. AC coupled: A designed circuit that doesn’t pass the DC component of a particular signal, DC offsets are ignored. Active crossover IC: An IC semiconductor or circuit which divides the audio signal into the proper frequency bands for the tweeter, mid-range, and woofer. Additive Color Processor IC: A color generation processor IC used in video that combines red, green, and blue to make all colors. Red, green, and blue combined together create a white raster on the video screen. Black screen is the absence of red, green, and blue colors. Accu-Rate Frame Lock (AFL): A patented technique of solving a problem called image tearing in LCD TV's which has to do with image scaling. This is especially present when erroneous motion video is in action, and this error happens when the input of the frame rate is faster or slower than the output of the frame rate, and a portion of the old frame and portion of the new frame are both displayed at the same time during the process of a refresh cycle. AFL patented system locks and sets the output of a frame rate to the input of a frame rate from a designated input. This produces an output that is free of image-tearing in a switching system which is seamless. American National Standards Institute (ANSI): A non-profit, private organization which administers and coordinates the voluntary standardization and conformity assessment system in the USA. Ampere (AMP): Base unit consisting of electrical current which represents the flow rate of electric charges going through a conductor wire. 1 amp is equal to current generated by 1 volt applied across a resistance of 1 ohm.

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Aspect Ratio: Physically comparing screen width to screen height, the aspect ratio of HDTV is 16 by 9 (16:9). Amplifier: A semiconductor IC or circuit used to increase the voltage amplitude of a signal. Amplitude: The strength or level of a signal which is measured by the vertical height of its waveform on a digital oscilloscope. Analog: A continuous action or movement that varies and takes time to change from one position to another. Basic standard audio and video signals are analog. An analog signal carries an infinite number of levels between its maximum and minimum value. Analog is a continuous range of values to interpret data (information), an endless resolution of values can be set in an analog system (circuit). Digital is different in that it changes in steps. Asynchronous: Continuous, not synchronized, or intermittent, its a kind of communication which permits two IC's (such as two buck chips) a signaling communication scheme that allows both IC's to signal each other when necessary instead of a prescribed (synchronous) timing format. Attenuation: Reducing the amplitude (strength or current level) of a signal. Auto-Input Switching/Auto-Switching: An IC or circuit that enables an LCD TV main board or Plasma TV main board the ability to detect which input contains an active sync-signal (such as a sudden HDMI input) and switch over to that input. Bandwidth: The complete range of frequency needed to pass a particular signal without distortion or data loss. A circuits bandwidth should be wider than the maximum bandwidth of the signals it may manage. A wider bandwidth means a more efficient circuit function with increased performance.

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Baseband: A primary signal (such as component video signal) including audio with a dedicated path which means it is not modulated on a carrier signal or coupled with other signals along a path. A video signal waveform is a baseband video signal. Bi-directional: the capability to transfer, move, or transmit in both directions. Signals can pass through in either direction along the same port by the same path. Bit-depth: The quantity of bits per pixel. Bit depth approximates the number of shades of gray or variations of colors that are displayed on an LCD TV. A bit depth of 1 will display just black and white as with a bit depth of 16 can produce 65,5360 various color tones. Bit depth is the quantity of bits used to valuate the chrominance and luminance of one pixel in a bit-mapped picture or video frame buffer. Bit error Rate: Fraction of bits which were transmitted with errors that are represented at the ratio of correctly transmitted bits or incorrectly transmitted bits. Black-Level: Also known as 'brightness' black-level is the level of light generated on an LCD TV screen. The magnitude of an image signal corresponding to the highest limit of black peaks. The brightness control sets the black-level. Buffer: Also known as a unity gain amplifier, a buffer isolates the signal source from the load and buffers are used in both digital (logic) and analog (linear) circuits. A buffer can also be a region of memory which is used to store data temporarily while being transferred from one process function to another. Bus: A dedicated path for transporting data signals, voltages, or a ground between various sections of an LCD TV main board such as a data-bus signal between memory and a microcontroller and/or peripheral circuits. The number of conductors (wires) determine the width of the data-bus line and the circuits that drive the lines determine the speed (data transfer rate).

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Chroma: Qualities of chroma include Hue and saturation, black, white, and gray are not properties of chroma, its the color intensity or purity which is also known as Hue. It is the color data separate from the brightness or the intensity of luma. A black and white TV image has an absence of the chroma signal. Chroma delay: An error in the video picture in which the color tone of an object or area of the screen has moved to the right side of the luma intensity. Chroma gain: In video, its an amplifier gain, as it means the level of color tone intensity in an active motion picture. Clipping Level: A circuit limit to protect against over-driving a video or audio signal. Clipping is cutting off (clipping) excursions or peaks of a particular signal. Its a type of noise (distortion) that happens when the excursions of a signal go beyond the threshold limits of the circuit. Common Mode Rejection: Measuring how good a differential amplifier rejects a signal that is present at the same time and is in phase at both terminal inputs. Valuated as a dB ratio with a corresponding frequency. DAC: Digital-To-Analog Converter Data: A representation of instructions/task in a format that's suitable for interpretation or communication. Representations such as analog quantities that have substance, value, or meaning. Data Compression: Math algorithms for compressing or encoding data to be placed with-in a specific bandwidth requirement for storage or transmission. DC Offset: The degree at which a DC voltage is bounced away from a baseline value or from zero VDC.

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DC Restoration: The proper blanking level for a video signal is zero volts. DC restoration circuit will clamp the blanking at a regulated level, and when set accurately this level will be at zero volts. Decoder: An IC semiconductor or circuit used to divide the RGBS (red, green, blue, sync) signals away from a composite video signal. Decoder is also an IC semiconductor or circuit in a syncronizer or programmer device which will read the encoded signal and configures it into a type of control. EIA: Electronics Industries Association An important Association which determines recommended audio and video standards in the USA. EMI: Electromagnetic Interference Unwanted interference, EMI is any electromagnetic disturbance which obstructs, degrades, limits, or interrupts the intended function of electronics/electrical equipment. Encoder: An IC semiconductor, circuit, or algorithm which converts data from one format to another. An encoder on an LCD TV main board will mix and combine Y (luma) with C (chroma) to generate a video image, or S-video (rarely used) is encoded (combined) to develop a composite video signal. Encryption: Data is manipulated into a coded format which can't be interpreted without another device which will decipher (untangle) the code. Error Correction: Method of detecting errors then reconstructing the original data using additional redundant data sent with the original information. It reconstructs the received signal into a dedicated reproduction of the original signal with-out any errors.

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Filter: A component or circuit which accepts what is desired and rejects what is not desired, different filters have different purposes. If there is a high frequency noise mixed with a signal, a low-pass filter is used to pass the signal and reject the high frequency (noise). Flash-Memory: A unique version of an EEPROM which can be re-written while still inside its operational environment opposed to being physically removed and programmed by a programming device. Frames Per Second (FPS): A data measure that is used to store and display a motion picture. Each frame corresponds to a still image and frame display in successions makes the illusion of motion. The motion pictures appears smoother if there are additional frames per second (FPS). Frame Synchronizer: Will store each input frame of video and releases it as the nest frame arrives. Frame synchronizers convert analog video into digital video and are generally used to synchronize multiple sources. Front Porch: Blanking or black portion of a composite image signal resting between the leading edge of the horizontal blanking pulse and the leading edge of the corresponding horizontal sync pulse. Gain: A common terminology for the increase of power in a signal or voltage produced by an amplifier, the quantity of gain is usually expressed in decibels (dB) above a given reference level. Gamma Correction: Before a display is generated the linear RGB information is required to be processed (gamma correction) in order to compensate for the gamma of the display. Genlock: A general method where the video output of a source or reference signal is used to synchronize other TV picture sources together. Sources of video that are Genlocked have vertical sync pulses that are synchronized together.

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Ground: An electrical circuit connection at a point designated as having zero potential. Its the electrical connection between the earth (earth-ground) and the circuit. Half Duplex: Transmission of A/V data than can happen in two different directions over a signal path but in only one direction at a time. Handshake: Its the moment when the transmitting and receiving IC chips on an LCD TV main board identify themselves to each other. For example a core processor on a main board handshaking with a supervisory IC on the SMPS board to initialize a power-good startup. HDMI (High Definition Multimedia Interface): Released to the consumer market in 2003 HDMI is a popular interface used mostly on LCD and Plasma TV's for the transmission of uncompressed high definition video images. HDMI typically has 8 channels of control and audio signals through a single cable. High Pass Filter: An IC semiconductor or circuit, that discriminates between low and intermittent frequencies and will only permit high frequencies to pass. Sometimes referred to as a low cut filter (cutting off low frequencies). I/O (Input/Output): The flow of signals or data (both in-or-out) in reference to a specific device or devices. Image: Imitation or reproduction of a thing or person from various kinds of visual media. Impedance: The load or opposition to a signal value that is measured in Ohms and which is abbreviate with 'Z' or 'W'. Low impedance circuits for video are low 'Z' (600 Ohms or less) or high 'Z' (over 10k Ohms or more) and 75 Ohms is the typical termination impedance for video circuits.

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Impedance matching: When a circuit generates a video or audio signal it is engineered to function with in a specific load value (impedance). It is vital that impedance specifications are followed and that the circuit load(s) are matched to the source. If not, unwanted effects like reflections, signal loss, and distortion of the original signal value will result from mismatch (unbalanced) impedance levels. Inductor: A circuit component (coil of wire) which opposes changes in the flow of current and stores the electrical energy as a magnetic field. Interlacing: The process of scanning a picture onto a video screen in-which the lines of one scanned field falls evenly in between the lines of the next proceeding field. Jitter: An unstable video image or a video image which appears to shake and causes viewing problems. Jumper wire: An extra or single conductor wire used to connect over (jump-over) other conductors at various junction points of an electronic circuit. Kilo: Represents the unit of 1000 for example 100K Ohms is 100,000 Ohms. Key Fill: A video signal that fills a hole cut in a background video by the key source. Keyer: A circuit which generates a control signal which is used to control a video multiplier which is referenced from specific information contained inside the video signal. LCD (Liquid Crystal Display): A glass panel which uses two clear sheets of polarizing material with a liquid containing crystals between them. LCD panels do not emit light and usually has a back-light source to illuminate the pixels.

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LcoS (Liquid Crystal on Silicon): A reflective display topology where a glass substrate is attached to a silicon chip that’s coated with crystals and this chip (wafer) contains the control circuitry. LED (Light Emitting Diode): A semiconductor component which emits an incoherent narrow spectrum of light inside the p-n junction. Line Driver: A signal amplifier which is used to expand a video signal over long extended distances, similar to a distribution amplifier (DA). Linearity: The capability of a display device to generate an object the same size at any place on the screen. Bad linearity will display an object at one size on the top of the screen and a different size of the same object at the bottom of the screen. Megapixel: Defines the resolution range (in digital imaging devices) when the quantity of pixels are equal to or greater than 1 million pixels. Modulation: A process of combining an information signal to a carrier frequency to permit it to be transmitted, and the carrier is modulated by the information signal (interfacing). Momentary key-Switch: This is a switch or switches found on LCD TV and Plasma TV keypad module, and these switches return to their normal circuit condition when the physical actuating force is removed. Mux (Multiplexer): A circuit or an IC chip which combines multiple signals for transmission over a single line. Then the signals are demultiplexed (DEMUX'd) or divided at the receiving end of the line. Native Resolution: A single fixed resolution of an LCD or Plasma TV matrix display topology. Its where pixels between the image source and display are properly aligned and does not require scaling or the processing of other signals. Its the resolution in which an image was originally produced at.

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Networking: Multiple chips or circuits communicating between each other and sharing the same data/signal resources. Node: One specific connected location or point on a network or circuit infrastructure. Noise: An unwanted signal that affects the quality of a TV picture or TV audio. Noise Reduction Circuit: A circuit or IC chip which reduces the the amount of unwanted noise in an audio signal or video signal. As the signal is compressed and then expanded the noise factor tends to be pushed-back which results in a much quieter signal. Non-Composite Video signal: A video signal which only has picture and blanking data and no sync information. Ohm: Unit of electrical resistance casting a current of one amp when there’s a potential difference of one volt. Output Power: unit of electrical energy expressed in watts or dBm. Overscan: Unwanted TV lines proceeding the limits of the display screen. Passive Crossover: Crossover network which separates audio frequencies using no buffering components or active amplification and only requires inductors, capacitors, and resistors. Pulse Code Modulation: A digital representation of an analog audio signal, PCM is also the standard form of digital audio for the audio portion of a digital video image. Peak: The maximum level of signal strength determined vertically (height) of the signals waveform using an oscilloscope.

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Peak White: The whitest area of a picture signal. Peak-to-Peak: This is the difference in the amplitude of a unit such as 'voltage' between its most positive and negative excursions. P-Frame: Predictive coded image which has predictive information needed to regenerate a video frame. Phase: Relative timing of one signal to another expressed in degrees of shift. Quantization: A process of sampling an analog waveform to convert its levels of voltage into digital data. Quantization Noise: Noise that happens from the quantization process. Deviation of a signal from its original or proper value. RAM (Random Access memory): Volatile memory that can be read from and written to, RAM is the functioning memory where active data and programs are stored. Volatile RAM looses its content when power is removed and non-volatile RAM keeps its content when power is removed. Raster: A series of scan lines that create a TV picture on the display screen. Raster lines are also known as scan lines. Real-Time: A network or system which delivers a correct value of data in the window of time and frequency in which it is needed. Reconstruction Filter: Low-pass filter in which its function reduces aliasing and smooths out the digital edges in an image.

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Redundancy: Repetitious data that provides a back up solution if the primary data fails at any time. Sample Rate: Rate at which an analog signal is sampled, a higher sample rate permits a higher frequency response. Saturation: Chroma gain, the intensity of color tone, the less white in a color tone the more pure the color or saturation will be. Saturation is the quantity of pigment in a color tone and not the intensity. Low saturation is adding white to a color. Scaler: A circuit or IC chip that converts video signals from one size measure or resolution to another. Also known as up-converting or up-scaling swinging from low resolution to high resolution, this is done to optimize or condition the signal which go's to the input of an image processor IC. Scaling: Changing the size of a picture to fit the original rate of a TV screen display without altering the picture shape. There are various techniques used for image scaling and some image scaling topologies are better than others. Serial Data: A method of transferring information by dividing the characters of a word into bits then they are transmitted in a sequential format along one path. Sharpness: Defines the edges of an object in a TV image. Termination: A load at the end portion of a signal line used to match the impedance of the circuit that generated the signal. The impedance absorbs the energy of the signal to oppose signal reflections from going back into the source from which it came originally. TFT LCD (Thin Film Transistor Panel): RGB pixels which are controlled by one or multiple thin-film transistors, these panels are also known as active matrix LCD's'.

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Time Code: A binary code or digital code which is used to identify each frame of a video, it is a form of hours, minutes, seconds, and frames. Time Division Multiplexing (TDM): Digital transmission method where a channel is separated into two or more timing slots or sub-channels in such a way where the sub-channels get segmented turns in the bit stream. Unbalanced Audio: Unwanted audio output either one of two terminal outputs is shorted to ground potential. Underscan: A vertical and horizontal reduction of the screen raster size in which all four corners of the picture image are visible on the TV screen. Voltage Control Amplifier: The output is controlled from its voltage being varied opposed to being controlled by direct resistance. Vectorscope: A specialized oscilloscope normally used in professional video systems to monitor chroma. Video Amplifier: Low-pass amplifier used to maximize the video signal for TV reception and transmission. Voltage: Unit of electrical potential difference expressed in 'Volts' also known as electromotive force. Watt: One watt is equal to 1 joule of energy per second, it is the unit of electrical power used to represent the rate of energy consumed or produced by an electronic circuit. Wavelength: Distance from one peak to the next peak between equal points in near-by waves of electromagnetic signals that are propagated along a wire conductor.

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White Noise: This is random amplitude over a wide frequency range, normally used to test audio speakers for sensitivity and resonance. XGA (Extended Graphics Array): This is a screen resolution of 1024X768 pixels. Y: Luma or Luminance Y pb Pr: Describes color space for progressive-scan of component video (non-interlaced). Y/C separator (YCS): Isolates Luma (y) and Chroma (c) elements of a composite video signal, it is the first process in decoding composite video. Z: Symbol for impedance.

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Recommended Resources List Of Electronics Spare Part Suppliers http://www.jestineyong.com/?cat=12 Electronics Repair Forum 1) http://forum.eserviceinfo.com 2) www.Repairworld.com 3) http://www.tv-forums.com/ 4) http://www.edaboard.com/ 5) http://www.tv.quuq.org/

Electronics Repair Websites 1) www.ElectronicRepairGuide.com 2) www.Anatekcorp.com 3) www.Epanorama.net/links/repair.html

Electronics Repair Membership Websites 1) www.ElectronicRepairGuide.com/Recommend/PlasmaTelevisionRepair.htm 2) www.ElectronicRepairGuide.com/Recommend/LCDTelevisionRepair.htm 3) www.ElectronicRepairGuide.com/Recommend/ProjectionTelevisionRepair.htm

Electronics Repair Ebooks 1) www.PowerSupplyRepairGuide.com

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2) www.LCDMonitorCaseHistories.com 3) www.LCD-Monitor-Repair.com 4) www.TestingElectronicComponents.com 5) www.FindBurntResistorValue.com 54 NOVACOM

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6) www.ElectronicsRepairArticles.com 7) www.electronicrepairguide.com/crt-tv-repair-ebook.html 8) www.electronicrepairguide.com/lcd-television-repair-ebook.html 9) www.electronicrepairguide.com/lcd-television-repair-case-histories.html

10) http://www.electronicrepairguide.com/learn-basic-electronics.html 11) LCD TV Repair Volume 1 12) LCD TV Repair Volume 2 13) LCD TV Repair Volume 3

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