Computer And LCD TV Repairing

24/09/2025

Operation Polarizer: A High-Stakes Rescue Mission Against All Odds

The patient was terminal. Its screen, a murky mess, seemed beyond hope. The diagnosis? A critically damaged polarizer sheet. Most would pronounce it dead. I saw a challenge.

The operation began under the cover of night. Tools laid out: surgical blade, chemical thinner, and IPA for sterilization. The first incision—disassembling the monitor completely. The goal: access the heart of the problem, the LCD panel itself.

The next phase was a delicate, painstaking dissection. Millimeter by millimeter, I scraped away the ruined film. The clock ticked past 3 AM, then 4 AM. Fatigue was the enemy, but focus was my weapon. Each pass of the blade, each wipe with a tissue, brought me closer.

The critical moment: applying the new polarizer. This is where missions fail. One spec of dust, one rushed move, and the entire operation is compromised. With steady hands, I aligned the sheet and began the slow, pressing motion—from the center out—watching for the tell-tale sign of an air bubble. None appeared.

At 6 AM, I connected the power. A signal flowed. The screen ignited, not with the ghostly haze of before, but with vibrant, brilliant color. Mission accomplished. The monitor lived to see another day.

02/12/2021

26/03/2021

This Panasonic CRT TV came to repair with the complaint of no sound. normally no sound fault are often because of bad speaker, broken speaker wire connection, Mute, corrupted EEprom data, missing dc supply to sound output IC, bad sound output IC and etc.
Once the TV cover was removed, I checked on the speakers first and located both of the speakers were good (have Ohms reading).

then, I checked on the DC supply to the sound output IC
On the DC supply side to the sound output IC, I measured and got 21.2 VDC but on the opposite side of the fusible resistor, I got almost zero volt. This usually indicate the resistor already opened circuit.
Since this can be a fusible resistor with low ohm (2.2 to 4.7 ohm), there is something had shorted that caused the resistor to open. Chances is extremely high the sound output IC was shorted.
When I set my meter to Ohms range and checked on the sound output IC vcc pin to ground, I’d got .001 Ohm that means it had a dead short . this can be it why the fusible resistor was open circuited.
I replaced both the resistor and also the sound output IC and powered it on, i used to be very happy to hear the sound came back again.

Assuming if there's no short and therefore the VCC pin to the sound output IC measured 21 Vdc, then my next step would be to direct replace the sound out out IC and retest. If still no sound then i will be able to reprogram the EEpr

21/03/2021

I received this TV with no life and once I plugged in nothing happened just the front red LED was blinking and therefore the TV didn't turn on!

After opening the cover I faced with three PCB circuit boards like power supply, main board and t –con board. I started with power supply all the output voltages are good.

In this model of Samsung TV, if power supply is ok but TV doesn't On, the suspect is typically EEPROM- IC 24c02n and therefore the program of this IC must are corrupted.

Since I even have the copy of this EEPROM IC, by using an EEPROM programmer it had been easy to me to overwrite the old corrupted memory.

19/03/2021

I connected the TV to power outlet and noted the TV was as dead. From my experience totally dead equipment no sign of life are caused by power supply failure and typically repair is simply considering that power supply section has only a few components and testing one by one.

I opened the tv and that i went straight to power supply section and began scanning.

Since the tv was totally dead, I started with the safely components and searching at main fuse I noted it had been darkened inside.

the fuse died under heavy stress and because of that never replace a fuse and apply power since it'll surely blow again.

if you see a darkened fuse expect heavy short ahead So I pulled my meter in continuity mode and tested across the switching transistor (S.O.T) between the center leg(collector) and therefore the emitter and got a beep either way.

That confirmed the transistor was short, I found the surge limiter resistor was also open.

After I checked the S.O.T driver transistor 2SC3807 and located it shorted base – emitter junction.

Kindly note that whenever you discover the switching transistor shorted (S.O.T) it's almost certain this drive transistor also has suffered plenty of stress and may get replaced otherwise chances of call back are high.

After replacing the four components now it's time to check the progress thus far and so I connected the tv to power source via series lamp current limiter.

After applying power, I noted the bulb was bright then dim and this confirmed to me no more shorted component on power board.

Before connected power directly without the current limiter i made a decision to search out what exactly was the reason for this short as there was no power surge within the area and therefore the customer confirmed that the children were watching the TV when it went down.

So i made a decision to check health of all main filter capacitors using my ESR meter and that i bumped on one capacitor on the B+ line rated 4.7 uF/160 V which has an ESR reading of 0.16K (160 ohms)

Usually when a capacitor ESR has gone up the voltage on it line drops and since the B+ line is very monitored, means the feedback circuit kicks in and advice the primary source to extend the voltage (drive fast) and this caused the S.O.T transistor to overdrive and hence short causing a series of other damages to the primary side of power supply.

So just in case I did not do further investigation and located the basis reason for this problem then it means it might just a matter of your time before the tv goes down again.

It’s time to power up the TV, And it had no audio(sound)

So back again to troubleshooting now the audio circuit and this tv was using ic AN7522N.

Searched its datasheet from internet and this what I got. Confirmed VCC pin is pin1.

I did live testing and that i got zero voltage on pin1, I checked backward trying to find what might be blocking this voltage and located resistor (R465) open.

I checked if the I.C was shorted, and was found to be okay.

I replaced the open resistor and applied power and noted the voltage 12 volts to the audio circuit is stable, this confirmed there's no short on it line and at last I re-assembled everything and after applying power I noticed the audio was now back.

15/03/2021

I believe those that are within the electronic repair line had found power supply that don’t produce enough output voltage. as an example, the B+ line of a monitor suppose to deliver 50 vdc but it only shows 20-25 vdc. All other ones output voltages at the secondary side dropped half. Faulty electrolytic capacitors with high ESR value within the primary power side could cause all the output power to decrease. any one know that a defective current sense resistor can also cause output power to drop? Yes, resistance increased within the current sense resistor could cause output voltages to drop into half. you cannot use normal multi-meter detect such low ohms resistor value (0.1-0.68 ohms). you'll get the esr meter to live accurately the worth of the sense resistor. If you are do not have the meter, just directly replace the current sense resistor and retest the equipment

14/03/2021

the LCD display has incorrect colors, noisy disturbances at black level and poor contrast picture as shown below.
This type of defects normally caused by the mother board or the T-Con board . From the TV channel display, it's unlikely that the most board failure because it is impossible for the video processing circuits within the main board to display
faulty on a particular area of the screen. Failure of the Mother board board or video circuit normally appear noisy or distortion of colors across the entire screen.

Most likely the T-con board BN81-01868A (V315B1) is creating the matter. as per the model this broad might be very costly. Replacing the T-con board are often the simplest repair job but it's not cost effective or might not worthwhile to repair it. a far better solution are to do to fixing the T-con board, since it should not be big problem because the major function i.e the timing controller is functioning fine instead the channel won't be ready to display normal picture except with the issues mentioned earlier.

Just to make sure I check all the dc voltages and didn't find any abnormality. so as to display the right color components, the grey scale or luminescence video part has got to be functioning normal a bit like during a CRT TV. i take advantage of a similar analogy to trouble-shoot the wrong color picture problem. it might be easier to analyses & diagnose the matter with analogue signals instead of the digital signals which is far more complex. I even have a ready DIY DVD grey scale pattern disk which I used it for CRT TV repair.

The analogue grey scale signal is apply to the LCD TV AV input and therefore the screen display happens to be abnormal grey scale image (see photo 1). From the abnormality and discoloration of the grey scale display, it's confirmed that the gamma correction or generator IC is not any longer operating normal and not performing gamma correction with the first characteristic. The gamma IC might be damaged which resulted in tinted color and noise generated being superimposed on the dark or grey level.

In the photo below is that the abnormal grey scale being display with noise and tinted grey scale. Switched to a channel you may be able to judge how the grey scale can affect the image quality
Most of LCD\LED TV manufacturers don't provide schematic diagrams for T-con board and there are limited information on the web . Spotting the gamma correction IC isn't
faulty as there are only a couple of IC’s on the board. The gamma correction IC on this T-CON board is showing as U6 with marking “ AS15-G” and it cost only around US$4.
After replacing the gamma generator IC (U6) the grey scale and television channel picture is back to normal without noise or discoloration and with good contrast level

13/03/2021

LCD TV 24″ came to repair with the complaint of red light problem. Red light means stand by power fault. It also mean no display until you've got sort the matter out. Stand by problem usually are often caused by bad power supply or The mother board. If Power supply is supplying good 5 volt DC then the fault is within the main board.

If power supply have only few volts ( 2 to three volt) this might mean power DC rail filter capacitor could have fault. So during this case, I got 5 volt DC output from power supply and that i measured it at the output connector pin 4 and 5 The DC 5 volt goes to the 2 boards (tuner and main board):
The easiest point to see within the mainboard is that the SMD transformer IC. check out the part number and see what is going to be the output voltage.

In my case, it had been the three .3 volt transformer IC. it's the input 5 volt but doesn't have 3.3 volt. it had been lowered than 3.3 volt!
Because of output voltage was lower that mean this particular IC could have problem. you furthermore may got to know that sometimes the lowered voltage might be caused by a leaky component along the three .3 volt line.
I replaced the IC and did a check on the output voltage. It was 3.3 volt! So this suggests there's nothing leaky within the 3.3 volt rail.
I lifted panel and saw the display if working or not. I replace everything and powered it on.
Conclusion- If after fixing the new 3.3 volt transformer IC and therefore the output voltage remains low then i want to see on the components that's connected to the three .3 volt power rail. It might be a shorted cap, leaky IC and etc.

08/03/2021

As you know that there are many numbers on the sticker of a flyback ? Which one is that the part number if Need to look In the Web for more information about the actual flyback? to save lots of time here’s some tips for you.

LG flyback- It start with 6174z-###x

Sampo flyback- It start with FEA###

Samsung Flyabck- It start with FKG-###XX, FKD-######, FQB-###### so on

Acer flyback- It start with 19.700xx

Some China made Flyback- It start with BSC######

In order to find out more about flyback part number, i suggest you search google and key in flyback manufacturer. From there you'll begin to understand as which part number that you simply should read.

08/03/2021

A bleeder resistor may be a resistor that connected across the outputs of power supply. Some designs use bleeder resistors and a few designs haven't any bleeder resistors in it. The function of bleeder resistors within the circuit is to discharge the filter capacitors as a security measure whenever power is turn off and to enhance the voltage regulation by providing a minimum load resistance.

In certain 17″ Monitor Flyback transformer you'll find a bleeder resistor parallel with inside capacitor. so as to Know resistant of the bleeder resistor within the flyback you want to have a meter which will qualify to many hundred mega ohms. in Monitor, the flyback divider besides act as control for the screen (G2) and focus, it also using as a bleeder resistor. That’s why, whenever a Monitor is turned off the high voltage charge within the internal capacitor in flyback transformer is quickly discharge by the flyback divider resistance. If you repair power supply, a burned out bleeder resistor is extremely dangerous because the capacitor still hold the charge!