Guide to repair LCD Inverter
2013-12-09
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Guide verification and repair of inverter modules for LCD.
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Cristian Garcia Martin
SERVICIOS TECNICOS IRIS
serviciotecnicoiris@hotmail.com
Av.Cataluña, 56-58 Bajos (Badalona) Telf: 93 4601505
Ctra.Antigua de Valencia,109 (Badalona) Telf: 93 3920090


INTRODUCTION

Before anything greet everyone/that wanted to read or take a look at these notes of which I speak always under my experience and knowledge. I'm a Spanish guy, more unusual, son of technical and forcibly compelled to learn with few or many tools that I have been able to purchase and thanks to the knowledge taught by my father or guild mates. I am 27 years old and many will think that perhaps he is too young to have experience, but I've been since age 15 workshop trying to improve day to day repairs and researching to bring affordable solutions.
Perhaps my age is what influence to me chances to try new things and that my physical faculties (sight, hearing and touch) have to 100% as always helps in this profession which, unfortunately, always just burning (perhaps I exaggerate) the view by forcing it to small tracks, welding, or micro-components that exist in the market today. These annotations to groso way, is a bit of what I can do after several months of fix faults in these gadgets (LCD) that ultimately bring us many headaches. We start off with the modules, inverters, as do checks and take deductions of the problem that we have in the corresponding device and later finish for solution giving you, that us is economic for us and the client. I am of those who think that change a module always is left to the end, when already your repair, but that the otherwise by impossible never learn and not only that, but which as I have said before, sometimes spending that can lead us to the repair of a plate, can let us rather more benefit than the change of new. I am a technician who can not give you incredible theory lessons for my lack of knowledge of theories, laws or protocols. But what I'm sure is that I will try to make some explanations simple, easy to understand for everyone, that technical engineer as to who has a device and is a handyman and you would like to make a repair without complications or questions. We will always speak of common failures of these modules, as no backlighting and therefore the lack of image but with existing sound. If the TV had glow on the screen it would mean that the module would be working correctly. When in doubt of the lack of backlight I usually LIGHTLY press the display with your thumb, getting that the liquid display let out a little more than light. If no meeting that glow, check inverter, but if this, unless we ruled out the possibility and will continue through other ways other than this.

INVERTER module is and is used for?

This module is used to generate a high voltage AC (alternating current) in the form of frequency starting from a low voltage DC (direct current), so what does not cease to be practically more than a converter from DC to AC, switched by a voltage. This high voltage is used to feed the rear lamps of a LCD display, and to generate light that can be seen the image, that is why they call you Backlight (rear light). As every electrical circuit is made up of several components, including highlighting some that another IC (Integrated Circuit) as for example the Driver, several transformers depending on as many bulbs as I have the display and several transistors type MOS-FET, is encapsulated with SMD transistor or IC MDS. For inputs and outputs have their corresponding connectors seeing clearly what is input (cable that goes to the power supply or the chassis) and which are outputs (wires toward the bulbs).

CONNECTIONS

Input: This part should be kept in mind, as this would be main to check. First I'll explain that are based on your entries and secondarily as ruled out in advance if the problem is of inverter or backlight, or if the problem comes from chassis or power supply.


This type of inverters is for small screens, whether they are portable DVD for laptops or LCD's very small. Only has a connector inlet and one outlet , therefore only works with a lamp. Normally its power is about 12" or- .At the same time, the lamp shall be placed at the top or bottom of the display, passing the light through a transparent plastic (kind of Metra quilato) , which leads the light by its entire interior. This type of inverters is for larger screens, typically up to about 23 ", has only a connector input and multiple output, in this case 4 output with a total of 12 legs, reaching the conclusion that it is for a 6 lamps. These lamps Irian located 3 on the top and 3 on the bottom of the display with the clear plastic or in some cases are positioned in parallel with the display, or behind the display. Its power also is about 12V, in this case with more amperage than the previous one, because you need more power in order to be able to boot to the transformers. It is typically in LCD tvs.


This inverter, not only fulfills its function but it takes an integrated power supply. On the one hand we need your input for power supply of 220V AC and on the other hand we have the other connector that will give us the signals relevant to the inverter and starting to turn, will be used to feed the main board (chassis) .The supply voltage you will be given by a rectifier diode accordingly filtered transformer that will come from the switched of the source. Their power will be about 12V. On the other hand we have 4 outputs for 4 lamps, which Iran located 2 at the top and 2 on the bottom. This inverter is used in monitors and LCD tvs up to 20 or 23" more or less.

This inverter has two input connectors (although it does not have to always be well and there are some that only carry 1), one is the power and the ground and the other also, but more a more takes the start switching and the relevant signals to operate. This type of inverters is powered normally 24V and need far more amperage than any of the others mentioned. On the other hand has 8 connectors and one separate appearing in this picture not it would go in the bottom corner to the left that it would be "common", so it is for a 16 lamps. This "common" can be a simple cable that goes to mass and all the lamps ends to make a potential difference in each lamp, or even on some models, especially in Samsung, they have 2 connectors for cable type FLEX, which is where all the ends of the lamps by independent thread. This type of display is used from 26 "to 37" or something as well, I can not assure that workshop has not yet entered any more than 32-inch LCD but if I have to say that if I don't I remember told me that they usually take 2 modules like this inverters and doing the same function but saving space.

This type of inverters are on the whole, one to the left and the other to the right. Have an entry each one, in the Master has power and control signals, and switching and the slave you reach only the supply and the earth. These inverters are normally fed of 24" and with enough amperage as in the previous case, about 4 or 6 amps or- .Each one has 1 output for the bulbs, each feeding a side of ends of the bulbs, or, for example the master feeding the left side and the slave to the right or even, by putting all the lamps in series and one of the loose ends that is giving you the power the master and the other end the slave. The connector for cable type FLEX, is only of interconnection between the 2 modules, it's not the same as the previous case to the ends of the bulbs. This type of inverters used in displays LG-Philips and only time I have seen it in 26" do not know if you have been in more inches.
With this more or less left a little redial the variants of inverters that there are in the market, now we are going to what is essential and common in the power inputs of the inverters.

Power:
I believe that it must not emphasize that it is VCC or VBL (CHI-MEI display).Its voltage can say that everything varies depending on the inches of display, the most common is that it is less than 26 "on a 12V and if it is more than 26", on a 24V.This tension only would be present when the appliance has booted, in STBY they wouldn't, since the power supplies for LCD are designed that at first normally take the microprocessor supply voltage (5V or 3, 3V) and the microphone once given the boot order to the TV, would send a starting voltage source, please switch the opto coupler from the 2nd source and leaving it 12 or 24V. If the voltage does not exist when the appliance is started, one of the main things to check would be the power supply, that should you boot the microprocessor switching to start the 2nd source, is usually a voltage between 3 to 5V that varies its been in STBY and booted, level high (3V to 5V) or low (0V).

Another possible failure and one of the most typical are the 1000uf capacitors that are positioned to filter the 12 or 24V in some cases i find that you put the same value, and the backlight device was trying to start and was not able or just starting up and last a good while it turned off the backlight and at the same time I noticed that the filter of 1000uf warmed up, these cases i have solved by adding one of 2200uf. On the other hand a typical failure in power supplies Vestel type 17PW,usually fail the 1or 2or the source (12/24V) some MKP capacitor, as for example in the 17PW15-6,fail the C878 or C877 to 15nF 1.6 KV,are the capacitors of the manifold of the switching transistor of the transformer of the 12/24V for the inverter, are often cut and the transformer does not oscillate well, even in some case i found myself with these sources that the appliance worked pretty well and when warmed up to the 2h is shutting down because of any of these capacitors. Other cases with the same source as the source vacuum i have the 24V but the plug to the inverter i came down and was also by the MKP and others simply nor be able to boot to the inverter giving 0V.

Other times I found myself the 1IC of the source or the 2nd not ranged and therefore had not in the 2or 12 24V.Como or in the case of a LCD DAITSU mod.- DL26A1/S with source brand Kisan mod.- KP-164FC,came the switching of the main board to start the source 2nd but didn't the 24V (display 26 " ) .The problem was the IC1 (type power transistor large with 5 legs), marked of nomenclature and 1M0880 was a KA1M0880. It was changed, and there was already the supply voltage to the inverter.

It should also be borne in mind that these 12 or 24V on the inverter goes to a fuse, and do not reach the mosfets. Sometimes it is cut by poor quality and others are cut by some Fet in cross cut or transformer. In cases where the LCD has an external source, usually also fail the 1000 uf capacitors or replace the feeder. If you decide to repair, at times I have had some that another problem with external power supplies, especially with the LI-chin, is that still fail even having filters are changed by being in bad conditions, the solution is resoldered all welds of the source, including those of the SMD components and with this work correctly. Another thing to keep in mind is that the inverter can supply amorrar or because the inverter is in poor condition (crossing or semicruce) or because the source of the sufficient power, in this case would have to put consumption in the line of 24V and with the inverter unplugged to discard what is the problem.
Boot order: usually called BL ON Backlight ON (), although in some devices they call it ON/OFF or ENABLE/DISABLE. This tension tends to be between 2, 5v to 5V STBY and its power-on State always is at 0V.This tension comes from the microprocessor that is what gives the order, but eye! normally in almost all devices, this switching and other signs of which we will discuss later, go in the main board (chassis) to source and supply to the inverter, typically in the source, will bridged pins the supply connector that goes to the inverter that it provides power, switching and operation. Normally this line do not tend to have problems, I found only one case carrying a Vestel 17PW15-8 source that he polled the backlight when I wanted to and it was because of BL ON. The tension that offered the micro was correct but then instead of going bridged cable going from source to the inverter, I went with a transistor by means, in particular the Q841, sometimes gave me only 1 to 1, 6V on the BL ON when I had to give at least 2 5V.I solved it by removing this transistor and thus always gave me the 2 power 5V and 0 in STBY. Another thing to consider is that if the micro does not start, i.e. does not generate a signal clock or data or both, either by the problem be, this signal would not have it, therefore should keep in mind that if this signal is missing us, would have to be sure that the micro works.


Brightness of bulbs: Most commonly called dimmers or DIM. This voltage is usually about 2.5 V to 3.3 V and more or less in both on as in STBY mode, this voltage is usually always to the same. The DIMMERS they say it s for the brightness of lamps, but in practice we cannot give more or less brightness in the image from this leg. The theme of the display brightness is controlled by the process of video. I have never found any fails for this line. We could also stress that there are several types of DIMMER (analog/digital) that are associated with this control, as I would be the PWM ,AND PWM,SEL , DIM, DIM D and DIM SEL.

Analog Dimmer: You may be called I PWM (Internal PWM used in displays CHI-MEI) or DIM (Dimmer analog) .It is always a tension or fixed or variant of between about 2.5 V to 3.3 V. * Digital Dimmer: You may be called AND PWM (External PWM,used in displays CHI-MEI) or DIM D (Digital Dimmer) .It is always a TTL signal of between about 2.5 to about 3.3 Vpp Vpp. Normally looking with an oscilloscope in this leg we observe how varies its amplitude to the beat of the image ,so to speak in some way it is as if you had an automatic control of the brightness of the bulbs, adjusting it always to the image you are seeing at that time.

Dimmer Switch analog/digital - can be called SEL (Selector, in displays CHI-MEI) or DIM SEL (Selection of dimmer) .This point or is at high level or low level and depending on the point at which this located is working with a dimmer analog or digital. For example, in the displays CHI- MEI, when this low-level would be switched the digital dimmer and against her when this high would be working the analog dimmer.

Error: Also known as INV ERROR or ERROR OUT. Some inverters carry this joyful leg and is responsible for informing the microprocessor of any fault suffered in the inverter. In some cases will not connected and in others, such as for example in sharp if that necessarily by design is connected. This pata in its correct state there are 0V,but at the time that determines that there is a fault, is generally made high level. In Sharp what makes is that after giving the error, the appliance does not start unless we ourselves in service mode (cancels the protection) and delete the error. This happens because it is registered in the memory of the device and when pulled up and starts the tv software, tells the micro that do not start by error in inverter. However in other brands simply in giving the order to error, short signal directly ON BL, but when we started up again, if the inverter has not suffered a damage ,turn back on the backlight without need to go into service mode as in Sharp. This pata can be overridden, in sharp still didn't try but in a display LG Philips if and did not affect the functioning of the LCD.

Note: Now we know which there are the patillajes, but in many inverters us the nomenclatures will not appear, nevertheless, knowing what it must have it is a question of comparing with a polímetro the tensions and not another good form of knowledge can be got out so that it serves every paw.Si so that each one serves one is lowering the datasheet of the IC Driver and doing a tracks pursuit, we would meet on the functioning(operation) of every paw. Another interesting thing and of big utility it is the power to verify a module with feeding and commutation externally. Knowing every paw so that it serves, what I usually do is to put the corresponding feeding bearing in mind the inches of the display (12 or 24V and with a minimum of 6 amperes), him(her,you) puenteo the paws of the commutation of ignition of unspilling (BL ON) with those of the control of Dimmer and I inject him 3V with another source and this way unspilling has to start(pull out). If it works we will see the resplendence on the screen and if it gives some problem of that cuts or that simply does not do the resplendence, unspilling is damaged by some place and we will continue with more tests.

Outputs:

As we said before, the inverters modules take an alternating current of between 1KV to even up to 3.2KV i have come to see, as always varying depending on the inches and lamps of the television. These high voltages the we got thanks to the transformers transistors switched MOS-FETS and even sometimes (depending on the inverter) by a few coils (inverter type Buck Royal). Also comment on some inverters that had at one end of the bulbs a common, normally this is going to mass, therefore to 0V and serves to create a potential difference between one end of the bulb and the common. When the ends of the bulbs are independent with a cable type FLEX at the top and bottom of the inverter module, if we punctured with the oscilloscope, we see that there is a return of the senoidal impulses that come out of every one of the bulbs. If there is any lamp cut or altered theren't deadened a change in the frequency.

COMPONENTS:

TRANSFORMERS


The advantage that we have to verify these transformers is that there are always more equal transformers with which to compare. The first thing of everything, it is necessary to know which is its 1st winding and which the 2nd one to what it refers of patillaje, since often they come to you with many sideburns which are only of adornment. Also it is necessary to bear in mind that there are some transformers that have 2nd two 1st and two, but that you will realize that it is evident for the tracks if they him(her,you) come to many paws or only to someone. When we know which are its windings it is necessary to compare them with the others, measuring with the polímetro in all the rest transformers, both in its 1st one and in its 2nd one. If we were detecting an enormous change in the ohms of one of the transformers to comparative of the others, this transformer would be altered and it can obtain that the module to unspill between in protection cutting the Backlight. The most common thing is that some winding of the transformer is cut. Another thing to be born in mind is that, on having measured with the polímetro in the windings of the transformers, if there was some damaged transformer, few solution would have since these transformers do not sell for free, unless we had of scrapping.
For the cases in which we were not locating the transformer or unspilling or simply out excessively expensive later I will comment to them on a solution in the paragraph of the IC Driver of unspilling. In case of replacing a transformer with one of scrapping it is necessary to be careful, since the transformers little by little are faltering and more if they already take a use for the warming that they suffer. I met the problems of replacing a transformer with another scrapping igualito and to a little time to come to me again with the same cut transformer, this is due to the fact that the IC Driver has a mental block and on having tried to start(pull out) extracts an excessive peak in the exit(departure) for the Mos-Fet, therefore in the amplification it will be evident moreover, the solution would be to annul the protection of unspilling so that the IC Driver has not a mental block. (To see the paragraph of IC Driver) Another thing to be born in mind in the transformers measurement is that there is times that if we begin looking at the ohms of the transformers of the ends, can be changing as we come to the center of the display. This is because they play with a balance so that the image reflecte better, they illuminate more the top and low(lower) part because it is where more darkness index can have and this way they manage to balance it. But these transformers if we notice have the same references therefore if we extract them out of the module and measure we will see that they all mark equally, but the culprit is the circuit that is designed this way.

MOSFET

We can usually meet several packages and of different types (N or P), among them, we will select a few examples:


2SC5707 FDS8958A

2SC5707: are these Mosfet transistor SMD-shaped, can be larger or smaller and at the same time they can be P-type or N-type.They are only a transistor and its physical lacks practically having to download the datasheet except in the event that we need the pinout or need to know its electrical properties.

FDS8959A: These Mosfet are shaped legs 8 SMD type 24CXX eeprom. In some cases like this are formed by 2 Mosfets and others in just 1, could also be the P-type or n-type For these Mosfet if that would recommend lowering datasheet before making any test, since they can vary their pinout. Personally when I need a datasheet, it always look for 1st on the web: www.alldatasheet.com normally all types of diodes, transistors and integrated circuits are located, and today the surf the internet looking for technical information is essential to the dearth of information on the latest technologies. When they are of the type as the FDS, normally only comes in the nomenclature the number, for example, in this case (FDS8958) only comes inscribed the 8958 and my way of knowing which is, is putting me in Alldatasheet, write the numbering and this database is prepared so that you locate the components that integrate into its "8958" nomenclaturelater down we'll see a big list where all related appear us. That's where our intuition gained from reading that serves this component acts (mark it then nomenclature:)

In this case would mark us the FDS8958 with Dual P-channel Powertrench MOSFET.Como see, because it tells us that it is a Mosfet and this if the open datasheet us block in the shape of our IC and with the same number of legs, would have all ballots to be correct. Any that again I found fault in module inverters in which everything appeared to be fine, but changing some Mosfet switching of transformers of the inverters finished working properly the appliance. These failures are usually find much in few lamps inverters, above all on monitors with a supply module integrated inverter. The most basic decisions is crossing to cut the passage of 12 or 24V fuse, since normally or van direct to the transistor or van direct to the transformer and for crossing as it is the first thing that would happen. Another case that I happened to any which again is that if a substitute Mosfet riding the original and we are not sure if they are the same characteristics (P or N), if you put the contrary usually or always leave the on screen or acts against, or when it needs to be on is off and must be turned off is on.

BUCK ROYAL coil (in the event the inverter take them)

As you can see in the picture that marked coil would be which I commented now. The vast majority of inverters I've seen do not carry it, but a topology is take into account. This coil serves to help work to the inverter, i.e., first an oscillation is generated in it as if it were a transformer, and then injected at the base of the transistor so that the transistor does not have to generate all the switching by itself only (at least what I think is).In theory the transistor would suffer less and be heated less. Failures are typical or good that this cut either fallen welds. When the bobbin thread has a considerable thickness, they normally fail welds since it would be impossible for you to remove. And when the thread is fine, normally the coil is burned and even causing them to be cut. They could also fail the welds. In the case of which was cut even I have not tried winding them again, but it is something that as soon as I have time and some module affected with cut coil, I'll try and I will comment. These coils are as original replacement, except to be a conventional coil, in that case we could locate something.

DRIVER these CI CI serve to give a train of impulses to the base of the Mosfet transistors for switching of transformers and generate high. They normally do not fail, of echo I think that I just found a case in that IC was crossed and there was no backlight. Among other things, should bear in mind its power, BL ON, everything to do with Dimmer and something very interesting, Soft-Start PIN. Normally these integrated are family OZ but over time we will be observing that there are many types. We put some very common examples with their pins:


TL494 OZ960

TL494: As we can be seen in the graph, its serious power (VCC) pin 12, its serious mass 7 (GND), the 3 would be the BL ON, the Dimmer do not remember well but I think that was the 13 (Output control) and the Soft-Start is the 4 (Deadtime control). The PIN 9 and 10 would be the outputs of the trains of impulses for the base of the Mosfets and the 1, 2.15, and 16 are lamps reference entries, longer that these integrated have them to get one or several references and if they will detect that it is not suitable they autoprotegerían and is apagaría the Backlight. This reference may vary by a cut lamp or a transformer cut or altered or anything in the area of high-voltage module inverter.

OZ960: Food is the leg 5 (VDDA), its mass the 16 (PGND), the BL ON would be the 3 (ENA, enable), the digital dimmer would be 13 (LPWM) and the analogue would be the 14 (DIM) and the Soft-Start would be the 4 (SST).11,12,19 Legs and 20 are the departures of trains of pulses for Mosfets and 9 (FB) would be the reference of the consumption of the lamps. The OZ, has both analog dimmer as digital, but only one of them will be that Act, depending on the type of circuit of the main board.

Note: Before commenting that the leg of the Soft-Start is very interesting, because here I've taken many repairs LCD. For example, when you have a LCD failing him the inverter and we can not repair it because it damaged a transformer or when there is a cut off lamp, there are few solutions that we can make it to repair, usually tend to buy the module for new, but sometimes or the inverter is too expensive or simply no longer in the market because this discontinued. My personal solution is to vary from State leg Soft-Start. So is the Soft-Start? We could say that it is a switch that positioned the IC State ON or OFF state. When I began to investigate the solutions that could reach have a module inverter based on measurements, me di account this leg changing state when it was the Backlight on and off. I came to the conclusion that these integrated working under a series of steps.
1-Power and polarization
2.-Start of Backlight
3-Verification of consumption (lamps return line)
4-Protection or continuity of operation (depending on if found abnormal consumption)
When this IC feeds, directly a tension out Soft-Star leg that goes to a capacitor (the other end of the capacitor will usually mass) doing a mass crossing and continuing giving a voltage from a 3V to 5V. Then I would do a verification of consumption and if it were correct it would continue maintaining the tension, on the other hand if it detects a wrong use, would make crossing the capacitor to ground and would be 0V, cutting the departures of trains of pulses. EYE!We are talking about in the case that the Soft-Star did it in ON a high level, also could do so at low level, will not be neither the first nor the last inverter you would find me to work at low level. Therefore, we could trick this leg to be always at the level high/low it position ON IC. Under tests 95% of the cases has gone me perfectly, but there are some who brought me a few headaches. As all tension, working to a home and that various time between ones and other tensions that we can locate the device. This bug only happens in the IC's that need the Soft - Start this at a high level to be ON, so it should go testing with a voltage of the appliance until you get one that works well, I put a few examples of cases I've found: 30 p LCD Medion LW-can inverter 48.V1448.001, bypassing the leg 4 (Soft - Start) the OZ960 with the leg 12 of the CN2 of the inverter (5V) LCD Jvc LT-30E45SU with Inverter 48.V1448.001, bypassing the leg 4 (Soft - Start) the OZ960 with the CN2 inverter leg 10 (3, 2V), with the leg 12 was not going well. LCD Philips 30PF9946/12 with inverter 48.V1448.021, bypass the leg 4 (soft-Start) of the OZ960 with 11 of the CN2 inverter leg, was not going well with the 12 or the 10 of the CN2. LCD Firstline FS30V with inverter 48.V1448.001, bypass the leg 4 (Soft-Start) of the OZ960 with the 10 of the CN2. LCD Orion LA-750 17 ", bypassing the OZ960 with the leg 7 (On/Off) of the CN2 leg 4 (Soft-Start). However there are others that put the leg to ground and is as simple as bypass the leg of the Soft-Start capacitor, its other end is mass. Examples: CI TL494: crossing the condenser that goes on the line of the leg 4 (Deadtime control "Soft-Start") to mass CI OZ972: cross the condenser that goes on the line of the LEG 8 (Soft-Start) to mass. 9777 CI: Cross the condenser that goes on the line of the leg 14 (Soft-Start) to mass.
This could apply it to almost all IC drivers of the inverters, the only that I was not even able to are in the inverter Master/Slave type. The first thing we should do to an IC that we know is get off the datasheet and search Deadtime or leg Soft-Start control. The small inverters, type to computer or portable DVD, usually crossing the Driver IC. It is the only ones that I found this IC fault.

LAMPS

Lamps can not be verified with tester, do not mark continuity. The only way to know if they're wrong is with oscilloscope and always and when the end that won't-powered lamps independent of the others and we could watch the turn making, if the input is good and the output is bad, this lamp is defective. If all output ends in common we could not verify anything with oscilloscope. HR Diemen has released a tool specific to this type of checks. www.hrdiemen.com


In the case that was cut a lamp, to change it would have to remove all the display and is an option to consider, since if you have no experience and careful, we run the risk of breaking the display a bit and then if it would be a device to throw away. You can also opt for the cancellation of the protection of the inverter and we could leave the inverter operating with all lights except that this evil. Another option that we would have is to add to the connector an at least 5W ceramic resistor, so we engañaríamos to the inverter, telling him that he has the correct lamp, therefore when it comes to check consumption does not detect error and would keep on. This reform is based depending on the inches of display, if less than 26 "is put a 33 K resistor - and if it is more than 26" add a few 56 k or-.If it doesn't work you go putting more and less ohms to locate a keep the inverter in ON. Lamps are bought by length and diameter of the same, if everything is the same one to another, in theory it could replace, but if we knew the tension at which they operate and the Khz which works as serious one point in our favor.

HOW TO ACT BEFORE INVERTER DAMAGED

First of all is to switch on the unit and see if it tries to shine a little screen, in some cases makes the attempt and some nothing at all. If you do try, means that initially the food arrives (12 or 24V) and that their boot and Dimmer polarizations in the beginning are correct. However make sure first of all, it could be that the power was low or source was not able to boot to the inverter due to lack of power. It could also be because the BL ON cut is either that the inverter gave a return to the micro for its leg of Error (in the case that had it) either because the micro detect external problems and cut. Verify connection to the inverter to rule out which is the problem. If the inverter does not make the attempt, it could be an internal or external problem. It should first check the connection of the inverter (power & control) if everything is correct could be that the inverter fuse was cut by poor quality or by crossing.If the problem is external that did not come you the power would have to check the power supply, above all the source 2nd which generates the 24V and the order which gives the microphone to jump-start to this part of the source of power (STBY).
On the other hand it could be that the micro did not give the BL ON signal, if it were the case, it would have to look at the micro worked well, that you were rocking and you to generate signals of clock and data and not only that but something very interesting to keep in mind is that there is communication from the flash (TV software) to the microand if there isn't, it would be normal that there is no BL ON. The first thing you would do in this case is to verify lamps with HR checker, since it is fast and should not focus on the circuitry, if any lamp is bad, either the exchange rate by resistance d 33 K or 56 k (depending on the size of the display) or will void you protection and would look if you notice it or notSince in some cases don't usually hardly appreciate and thus should not be handling the display and remove it completely. Once ruled out the entry of the inverter and lamps, practically all the inverters (common fault) always make an attempt to illuminate and cut.Before this fault I what I normally do is to verify the transformers. If there is any evil and their position is not that of most top or very bottom of the inverter, remove the top or the bottom and I put it in the wrong position and bad if it is to only leave a lamp without (at the top or bottom), unlike if it were for two lamps would have to verify if any of the other windings are this good and bad I leave it unconnected and always the here or at the top or at the bottom so that it always stays as much without illuminate those parts, since it would be less where you realize at first glance.
If transformers were good, the next thing I would do is check cross in any Mosfet. We speak in these cases of rapid tests of continuity with the hand Tester since we can more or less rule out areas of the inverter if lose big time. If there is any evil and didn't know exactly what, remember the search on the nomenclature of the mosfet www.alldatasheet.com and find that more simile have to us, physically as well as its operation. If all this correctly, what I would do is verify the entries and exits of the Driver IC.Mainly food and secondarily the Soft - Start status, if various high level or level low depending on whether is in STBY or ON and if all is well I directly go to transformers (1 to 3 and peak KV) outputs, or directly on the connectors on lights so you know exactly which line is the wrong. Starting from there would be question verify the components of this line (capacitors, transformers, mosfet output impulse train Driver IC to mosfet for that line, etc...) If IC did not come out of first train of impulse, above all there to verify the input of the BL ON the IC and the Dimmer with their corresponding functions. It should take into account that the inverters if they detect something wrong on this plate, short entering protection, so tests must go by them by turning off and turning on the appliance whenever it enters protection. Some typical bugs are welds of transformers, some again electrolytic capacitors the inverter or even some Mosfet internally not working well although making measurement appear to be fine. In the case of the MosFet, serious change by trying, since some cases I've gone crazy looking for a measurable failure and at the end has been one of them failing.

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JAY - 2017-01-23
This item is very good for repair professionals