The criticism for this particular LIKOM 15″ L4031NDG Monitor wasn’t any display and has electricity. Well, no display can be no significant voltage, failure in G1, G2 and furnace circuit, faulty flyback transformer, failure in film tube and Micro Processor or even several other explanations. In order to learn the answer we have to turn to the keep track of. Up on switching to the monitor, I was not able to hear any noise from the screen but also the ability led is on (green light). You can’t feel some static at the glass of this tube. This might be an indicator of no high-voltage manifestation 2cl71.
Anyhow, I have to use my loyal Kaise SK9000 high ion probe to check if the high voltage present in the anode. Sometimes in the event you fail to have that the inactive in the glass of CRT, doesn’t signify that the superior voltage isn’t present. It’s just reduced in high-voltage; state could be 10 to 12 kilo volts. Low top voltage and also no high voltage are totally two different symptoms. In the above mentioned case, my high voltage probe registered zero volts! So it’s confirmed no high-voltage issue.
There are many good reasons for no high voltage problem. A lost Bvoltage, a defective flyback transformer, no horizontal drive pulse from h/v oscillator ic, missing or low supply voltage into flat driver transformer and could result in no highvoltage. The first point I have assessed is that the flyback internal capacitor-the capacitance is over the ordinary scope which is 2.7 nanofarad. If the interior capacitor is shorted, then it would induce no high voltage. The next point I have assessed to become fine is that the Bvoltage. It revealed about fifty + horsepower and this also mean there’s supply entering the B+ pin of flyback transformer.
When assessing the next point (the voltage in the first winding of horizontal flyback transformer)I found that it has zero volt which is very odd. The base drive electricity supply input has approximately 14 liter but following the resistor it revealed zero wattage (by proper it should have approximately 1 2 volt-voltage drop right after the resistor). As soon as I placed my finger over the base drive energy resistor shortly after switching off the observe, ” I could believed that it was hot. This is that which we predict a hint. A excellent working base drive electricity resistor will not acquire sexy until it burns off your finger! There has to be a thing that has gone wrong or shorted which creates the ability resistor turned exceptionally hot. By the end we get, we are able to express that the horizontal travel circuit is needing difficulty that my focus will be about this circuit.
A shorted horizontal driver transformer main winding, flat driver transistor, elements encircling this particular circuit can cause the energy resistor to become hot. The horizontal driver transformer primary winding could be assess using a dick smith fly-back tester while the horizontal driver transistor and encircling components might be test with an ordinary multi meter. The end result, astonishingly much one component within this circuit saw to be defective.
Since it wasn’t possible for me to locate the faulty parts, the single way to find out the culprit would be to come out with my very own drawing foundation on this monitor circuit (using track circuit concept to solve trouble ).
When the track is turned on the h/v oscillator tda4858 is going to receive a source voltage approximately 9 12 liter from electricity source. Subsequently it may ship a square wave heartbeat into horizontal driver transistor as a result of snare 7 (flat motorist output) to induce the transistor to modify. As soon as the flat driver is switching the flat driver transformer would work and also an base signal has been generated to turn on the Horizontal output transistor (HOT). This very hot would subsequently drive the flyback transformer and 24 kilovolt would appear at the anode.
I questioned myself what should the h/v oscillator ic tda4858 instead of providing a square heartbeat, it create a more consistent sign? If it sends out a consistent five liter sign to the horizontal driver transistor, then this transistor wouldn’t swap and causing it to turn”on” all the time. When that take place, the bottom drive power resistor along with the horizontal driver transformer primary twisting might experience. The bottom driveway energy resistor and also the horizontal driver transformer primary winding today might behaves much like a filament or perhaps a lamp! . No ramble the base drive power resistor was becoming hot when the screen was switched .
After carefully researched the horizontal drive circuit, I’ve made the conclusion it had been the h/v oscillator tda4848 that transmits a wrong signal causing the base driveway power resistor to find hot and in the same time inducing no high voltage from the track. I used to not use an oscilloscope to check on to your square wave in order to confirm my theory accurately because I am very certain that it was that the h/v oscillator IC that output wrong signal that caused no high voltage.