REPAIRING AND NOT THROWING AWAY

REPAIRING AND NOT THROWING AWAY

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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Saturday 16 February 2019

IC UC3842 GOOD OR BAD WAY TO EVALUATE

IC UC3842 good or bad way to judge


POWER SUPPLY PWM IC 3842.

Among the domestic electronic equipment, power supply PWM control circuit is the most commonly used model is the integrated circuit UC3842 (or KA3842). That is because often encountered, there are also some of it was, following a brief UC3842 good or bad way to judge:
the complete replacement of the damaged peripheral components, do not install the first switch transistor (MOSFET), power-measuring 7 feet UC3842 voltage, if voltage fluctuations between 10-17V, the rest of the foot were also fluctuations of voltage, then the circuit has been start-up, UC3842 normal; if the 7 pin voltage is low, and the remaining pins or no voltage fluctuations, the UC3842 is damage.

In the UC3842 7.5 feet between the left and right external +17 V DC voltage, measuring 8 feet if the +5 V voltage, 1,2,4,6 feet have different voltages, the UC3842 normal, current is small, its easy to damage . It is the most common cause of damage to the power switch transistor (MOSFET) circuit, the extremely high voltage from G added to the 6 foot walls to burn. And some models eliminates the need for the protection of the G grounded diode, the power switch transistor (MOSFET) is damaged, UC3842 and G very external current limiting resistor must be bad. At this point a direct replacement.
Note that the power switch transistor source (S pole) usually take a small resistance, the resistance of high-power sense resistor as the overcurrent protection. This resistance is generally between 0.2-0.6, there will be greater than this value can not afford to load with the phenomenon (that is, sub-low voltage).
As the UC3842 (KA3842) operating voltage and power output are related to UC3843 (KA3843) falls far short of 3842 series and 3843 series off voltage in the starting voltage and also there are large differences between the former start-up voltage of 16V, turn off voltage 10V; the latter starting voltage of 8.5V, off voltage 7.6V. The two series of IC can not be directly substituted. If substitution is necessary to use the latter when the former should be to transform the circuit. Therefore, this point in the maintenance work must pay attention to.
Posted By: FRANK at 04:20
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