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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All posts are presented here for informative, historical and educative purposes as applicable within fair use. NOTHING HERE IS FOR SALE !

Saturday 7 November 2020

HOW TO MODIFY LCD TV CCFL INVERTER WITH AN UNIVERSAL INVERTER CA255


......... IF A technician plans to modify the Back Light CCFL lamp (a kind of fluorescent) an LCD to be A
Back Light Led lights.
Vcc voltage available  Back Light on 12v POWER.
The total number of Back Light Led lights installed. is 27, so the required Back Light Inverter Out voltage is approximately 27 x 3v = 81v.
 

So i decided to buy the Universal Back Light Inverter type CA-255, because it met the requirements of "input voltage" and "output voltage".

But after installing and trying it ………
.. FET is so hot ... ..and it doesn't take long to die short.
What's wrong here ???
Where did it go wrong ???

Obviously .
This Universal Back Light Inverter is manufactured or designed "not for modification" from CCFL to LED
But this universal Back Light Inverter is actually made and designed to "replace" the defective Back Light Inverter circuit according to the existing Vcc input voltage and according to the number of existing led lamps.

Try to pay attention to the various voltage specifications of the Back Light Inverter led that we have ever encountered.
Each pay attention to the Vcc-Input voltage and Back Light-out voltage.

Then the Back Light-out voltage is generally a maximum of only 3 x the Vcc-input voltage.


So for example like the picture above.
To get 88v out voltage, the input voltage must be 28v.
Or more or less is 3 x the input voltage.

So from the example of the case story above.
The inverter has been forced with a Vcc input voltage of only 12v, .......... so that the output voltage is up to more than 80v.
This means that the output voltage is almost 7 x the Vcc input voltage.
This forces the PWM drive pulse width for the FET to be wider (longer on period) .... which causes the FET to heat up.

What is the solution to the example above ????
With an input voltage of only 12v ....... so to be safe the maximum output voltage should only be around 3 x 12v or 36v only.
So the solution is to change the total series of existing led lights ...
Changed to combined series - parallel.
For example, from 27 led …… ..diparallel into 3 parts…. Each part consists of 9 leds in series. So that the inverter output voltage needed is only around 9 x 3v or 27v.

Posted By: FRANK at 07:25
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