Dell 20
Dear Tirat
Hello Dave, well unfortunately your problem here is not going to be all that easy to resolve as components that burn out are not always visable to the naked eye. However, there are logical methods of approach that you can undertake to possibly find out and recify what has caused this fault. Let us start by looking at the supply signal (DC current) that is received into the monitor unit. By using instruments such as multimeters and oscilloscopes on components at power supply source, you may be able to work out ifany of the crital parts have broken down. For instance, Capacitors are rated on the farad scale or microfarad in the case of small DC circuits carrying low voltage (uF). So it may be worth checking service sheets in order to find out what the read ratings and load ratings are, then compare them to the read ratings you have.....If they dont match, then you have found the fault at supply source, and the same methods can be applied throughout the entire DC circuit. It is time consuming, but it will make for a good project, and if you find the fault, then components are fairly cheap to acquire from either partstore.com or maplin electronics.
There is one other possible reason for the smoke and no burning marks, an that is tha you have only concentrated on the main PCB, so i recommend looking at the back-light and LCD Unit itself. Both of these components carry large enough voltages for smoke to be produced, and the burn/ scortch marks are not so evident unless you ae specifically looking for them here. What you will be ooking for, is a small strip-ligh or florescent type tube with either smooth soft white or black wires attached to it, the insulation of this wire is smoother and largely differs from that of other wiring within the unit, so this component will stand out to you.....Once you find the tubing, if it has been burnt, or had a fire the tubing will have been broken, and you will need to replace this and first find out what caused the fault to happen in the first place....WARNING....LCD SREENS AND CERAIN COMPONENTS CARRY HIGH CURRENT AND VOLTAGES THAT MAY BE HARMFUL IF YOU COME INTO CONTACT WITH THEM, SO BE SURE TO POWER DOWN, AND PROPERLY DISCHARGE THE UNIT FOR 24HRS MINIMUM BEFORE UNDERTAKING ANY DIRECT CONTACT WITH COMPONENTS. IF IN DOUBT, CONTACT AN APPROVED SERVICE ENGINEER.
So as said, your best bet is a logical systematic approach, deal wth the supply source first, then trace back to the display in order to find your fault. The other main reason for this is that to replace a power supply and a few components at supply source within the monitor is cheaper than shelling out for a new screen and backlight. So always start with the cheapest first.
Lastly, your other indicator that you may have either blown LCD or backlight is evident if the power LED (green light on screen) is on, but you get no picture, however this can vary from model to model, as the internal circuitry is arranged differently on other monitors, but its still well worth a look.
I hope that this has proved useful for you, and if you do need further assistance, then please do not hesitate to mail me back as so i can assist you further, i will b here pretty much all the time, so just feel free to ask me or comment, nd i will endeavour to respond
yours sincerely
oz
