Master Electronics Repair !

Welcome to Master Electronics Repair! website.Here you will find:Service Modes, Circuit Diagrams,Service manuals, Firmware Update procedure, Disassemble procedure, Universal remote control setup codes, Troubleshooting, Diagnosing, Measuring, and more.... of many of LCD/LED TV/Displays,others various electronic apparates,trough many technical notes and tips/tricks to help repairing/fixing Troubles/ faults,for electrical technicians.This site helps you to save the Earth from electronic waste!

Richtige Fernseher haben Röhren!

Richtige Fernseher haben Röhren!

In Brief: On this site you will find pictures and technical information about Service Modes, Circuit Diagrams, Firmware Update procedure, Disassemble procedure, Universal remote control set-up codes, Troubleshooting and more....

If you go into the profession, you will obtain or have access to a variety of tech tips databases HERE IT IS Master Electronics Repair !.

These are an excellent investment where the saying: 'time-is-money' rules. However, to learn, you need to develop a general troubleshooting approach - a logical, methodical, method of narrowing down the problem. A tech tip database might suggest: 'Replace C536' for a particular symptom. This is good advice for a specific problem on one model. However, what you really want to understand is why C536 was the cause and how to pinpoint the culprit in general even if you don't have a service manual or schematic and your tech tip database doesn't have an entry for your sick TV or VCR.

While schematics are nice, you won't always have them or be able to justify the purchase for a one-of repair. Therefore, in many cases, some reverse engineering will be necessary. The time will be well spent since even if you don't see another instance of the same model in your entire lifetime, you will have learned something in the process that can be applied to other equipment problems.
As always, when you get stuck, checking out a tech-tips database may quickly identify your problem and solution.In that case, you can greatly simplify your troubleshooting or at least confirm a diagnosis before ordering parts.

Happy repairing!

Today, the West is headed for the abyss. For the ultimate fate of our disposable society is for that society itself to be disposed of. And this will happen sooner, rather than later.

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..............The bitterness of poor quality is remembered long after the sweetness of todays funny gadgets low price has faded from memory........ . . . . . .....
Don't forget the past, the end of the world is upon us! Pretty soon it will all turn to dust!

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Thursday 7 February 2019

LG21FJ6 – COLOUR TV – CIRCUIT DIAGRAM – MAIN COMPONENTS

LG21FJ6 – Colour TV – Circuit Diagram – Main Components

To protect the picture tube and FBT,the average beam current and peak beam current may not too high. The beam current limit information and High Voltage (H.V) tracking information are derived from the H.V voltage winding of T401

1. The contrast and brightness reduction of RGB is proportional to the voltage on the pin 48 of IC501.

2. As the beam current (slow),and H.V (fast) are changes, the voltage of point A is changed.
3. By the increase of beam current, the point A voltage is decreased and this information is fed to pin 48 of IC501.
> Contrast reduction begins when V49 is below than 3.1V.
> By the more increasing of the beam current, the V48 decreased and eventually when this voltage is less than 1.8V the brightness reduction is started.

[Check the value of R416, the resistor connected to +B for (open); if the ABL action is not detected. This is a common fault to this set.] Deflection SECTION

1. The H drive output is open collector and active low, I.e. the H-out TR should conduct during the low period of output.
2. Under normal operation condition the duty cycle of the output pulse is 50%.
3. To ensure a smooth start/stop behavior of the horizontal deflection and protect the H-out TR, there are 3 different condition of H-drive output.

During switch-on. The horizontal output starts with the double frequency (31KHz) and with duty of 75 %(off),25%(on). After about 50mSec of switch-on. The frequency is changed to normal value (15.625KHz) and duty cycle to 50%.

During switching-off. Also the frequency is switched to the double value and R.G.B drive is set to Max. and after 100mSec R.G.B is set to Min. and 50mSec later the H drive is switch-off.
4. The H drive pulse from the MICOM (IC 501) is amplified by the horizontal drive circuit, to get sufficient base drive current for the high voltage switching TR (Q402).

If the horizontal output transistor [2SC6093] found shorted (Collector to Emitter short); before replacing it with an other one, check the solder terminals of the C414; for any loose. Check the capacitance of this capacitor. Any failure (Capacitance value deteriation or Loose solder), to this capacitor will damage the horizontal output transistor.

You won't get any time to check any voltages. The damage to horizontal output transistor will be instantaneous, as you power on the circuit.