Dell E151fpb LCD monitor came in with the complaint of no power but upon carefully look at the LCD you could see a very light (blur) white flashes across the screen and the power LED is not lit. Removing the cover was a bit easy compared to other models. As usual whenever the mainboard and power board were exposed, I would look for any bulged capacitor, darkened area, a loosen connector and etc. However this monitor boards looks perfectly okay. The next step was to separate the power/inverter board with the main board. Power was applied to the power board and I could hear a soft ‘chip-chip’ sound. When I measure the 12 volts line with a digital multimeter, the readout was about 7- 8 volts which was very unusual. In fact this is good news to us because we know what the next step that we should make.
Now we could use a 12 volt automobile brake light bulb to test at which section that is causing the low voltage output problem. If the LCD monitor designed to run on 18 or 24 volts then you could use a light bulb from the big trailer. A defective component in either primary or secondary side could cause low output voltage. Removing the fuse as shown in the photo and connect the bulb between the supply line and the cold ground could tell which section is giving problem. You could use this method but first you must confirm that the secondary filter capacitors, TL431 adjustable precision shunt regulator ic, optoisolators and components surrounding the optoisolator is working before you proceed to use the light bulb.
When the power is on the light bulb still do not lit and the sound still could be heard. This indicates that the primary side is having problem and we can leave the inverter/high voltage area and fully concentrate to locate the faults in the primary section.
This is the time to really test your basic electronics skill because you now know at which area the fault is and you just have to use your skills to locate the exact bad component. There were not much components in the primary side, and you could easily check all of them in less than 20 minutes. After checking all the components I was surprised that all of them tested okay. Primary winding of switch mode power transformer rings 8 bars which indicates good and even the uc3842b PWM power IC replaced the power still won’t work! It was quite challenging to troubleshoot this kind of problem where you are hundred percent sure that the primary side is giving problem yet you could not find out the culprit.
Since I had checked all the components and could not locate the fault, the only way that I could do is to direct replace the semiconductor devices such as the diodes, scr, fet, and transistors. From experienced I do encountered semiconductor components breakdown when under full operating voltage. One by one of the semiconductor components I replaced and power on each time I had changed it to see if the bulb light up or not. Guess what, you would not believe what have I just discovered-a defective 2N7000 fet! The moments I have replaced this fet and power on, the bulb immediately light up. I could not believe it was this faulty fet that causes all the output voltages to drop! I was so happy that I eventually solved the problem and who knows this could be a common fault for all DELL E151Fpb LCD monitor- so please take note to all LCD monitor repairer.
I began to check again the defective 2N7000 fet with my analog meter and peak electronic atlas component analyzer and the result is still the same-tested good! Just like flyback transformer, the best testing equipment to test Fet and other components is actually the equipment itself because it runs on full operating voltage, frequency, signal and etc. What you have just learned from here was that if all the suspected components tested good, the only way to reveal the truth is to direct replace the parts. Hope you enjoy this article and more good articles to come everyday! Wishing you all the best and happy repairing!
By: Jestine Yong
Archive for February, 2010
How To Repair Dell E151Fpb LCD Monitor – No Display Problem
February 27th, 2010Power Tool Batteries
February 22nd, 2010
Power tool manufacturers now offer many more cordless power tools than before, so the demand for power tool batteries has gone up as well. Power tool batteries vary by brand. Some of the most popular brands are DeWalt and RYOBI. Black & Decker is also another favorite. Power tools are built with a specific design of power usage that cause batteries to differ greatly from tool to tool, and from brand to brand. A new cutting edge lithium ion power tool battery has recently been released on the market which will make power tool batteries even more effective. The invention of cordless power tools has made construction and other tasks involving power tools much easier.
Specific brands have their own specific batteries. DeWalt Tools have a specific battery serial number for their different tools. For example, a certain DeWalt tools use an 18V whereas other will use an 9.6Volt. DeWalt battery serial numbers begin with the letters DW followed by 4 numbers. Black&Decker has a long list of batteries as well, ranging in voltage from 9.6Volt to 18Volt. RYOBI brand power tools have a much smaller list of batteries than does DeWalt or Black&Decker, and none of these batteries can be interchanged between brands. However, brand makers have started making batteries interchangeable between tools so consumers can purchase a package set of a good variety of tools, that all use the same interchangeable, rechargeable battery. For example, RYOBI has a set that includes a saw, a drill, and a flashlight that all use the same 18Volt battery. These sets usually come with two batteries so the user will almost always have a charge battery in stock.
Cordless power tools and power tool batteries have been improved greatly in design since they were first released. Higher voltage batteries make cordless power tools more powerful and weigh less. This enhanced design makes power tools more user friendly, more ergonomic, and easier to get into hard to reach spaces.
Most current power tools use a NICD batteries. However, a new lithium-ion battery has recently been released for Black&Decker that is said to last ten times longer than traditional lo batteries. It is also said to charge to 90 percent capacity in 5 minutes. Lithium ion batteries used for power tools are only 3rd in demand behind laptop and cell phone batteries. The release of this new battery be very useful to users because they do not suffer from the same memory effect that is found with NICD batteries.
Cordless power tools have changed the way many people work. Higher voltage allows batteries to work much better and last much longer. For the price of powertool batteries, upwards of $50, users want to get the most for their money. The release of the new Lithium Ion batteries will only further enhance cordless power tools.
By: Angela Oliver
Softball Cheers
February 22nd, 2010
Several hundreds of softball cheers are available online that can raise the spirits of softball players. The word “cheer” means to give encouragement to someone. It can also mean showing approval or wishing good luck by shouting, and cheerfulness is the quality of being happy and dispelling gloom.
Some nice examples of softball cheers are:
“Potato chips, potato chips, munch, munch, munch. We think (opponent’s team name) is a mighty fine bunch!”
“Two, four, six, eight, who do we appreciate? (Opponent’s team name)”
“You gotta want it, to win it, and we want it more!”
“Two pence, four pence, six pence, a dollar. All for the (team name), stand up and holler!”
“When you’re up, you’re up, when you’re down, you’re down, when you’re up against our team, you’re upside down!”
“(Teammate’s name twice), she’s our star, she can hit it mighty far, put a bat in her hands, she can hit it to Japan!”
“Swing that bat and bust that ball honey, honey, swing that bat bust that ball babe, babe, swing that bat and bust that ball round those bases yehaw, honey oh babe oh my!”
“Five, four, three, two, we’re number one, can’t be number two, we’re gonna beat the whoopsies outta you! Don’t feel sad, don’t feel blue, we’ll let you be number two!”
“You seen it, now hit it, go, go and get it, you seen it, now hit it, come on (name), get wit it!”
“(Player name), you’re the one (repeat), hit that ball and run, run, run, around the bases you shall go, first, second, third and home”
“You the one, you the one, you the one, you the one, say what, say what, say what, you the one, you the one, you the one, you the one, the one, the only one!”
“R-I-P-I-T, rip it for me baby, rip it (clap 4 times), (repeat).”
These softball cheers are from the “Rancho Trabuco Girls Softball Association (RTGSA)” website, but several others also have a nice collection of softball cheers. These above mentioned cheers and many others could truly be an excellent source of enjoyment, and encouragement.
By: Kevin Stith
