Benq lcd tv
posted by zippie on Aug 09, 2007
a friend brought me a 30" benq lcd tv. the problem is this thing powers up, the backlight comes on briefly and then goes out. no matter what input i use - component, vga, dvi, or composite - it will not light. the display is black, the power light is on green and the fan in the back of the unit is spinning. tried using the "i" key on the remote or the input key on the top of the tv - no result. with a dvd player, sat receiver or a pc - nothing works. every time you turn it on the same thing - brief backlit black screen then a totally black screen. any help would be appreciated.
Zippie
p.s. i build computers - so i am comfortable with electronics, just not an expert.
Comment by zippie, posted on Aug 10, 2007
well...i just spent the better part of 2 hours disassembling this monster - it turns out there are 16 flourescent tubes directly behind the lcd itself, with a mass of filters as well. i cant see all 16 going at once - maybe one or two...but not 16. i assume you would come to the same conclusion. so that would leave me at the inverter board or the "on" signal coming from the processor. your thoughts?
Zip
Zip
Comment by zippie, posted on Aug 12, 2007
see....now i get more information from the owner - apparently in the last few months he has had to remove the back of the unit to get it to work...woulda been nice if he told me that when he brought it over. I guess i muddle through and see if i can find evidence of overheating and/or burnt connections. some peoples kids i tell ya.
Best Solution
posted on Aug 09, 2007
GuruHi zippie,
Based on your post/description, I am inclined to suspect the backlight which is actually a CCF a small fluorescent tube about 2mm diameter the width of your display either at the very top or bottom of the screen. At times it can also be the inverter circuitry that powers up the said tube. One way is to run your PC and display as if nothing is wrong giving it a minute or soto finished booting everything. If looking closely you will notice semblance of your desktop albeit very faint, very dark or using a flashlight provide illumination to the display at an angle and the display is there, then chances are it is the backlight. Otherwise, it can be the input circuitry. Of course you have to open the monitor up and replace the defective component, More often than not no soldering required. Hope this gives you an idea or two. Lots of luck and pls post again how things turn up. If
Based on your post/description, I am inclined to suspect the backlight which is actually a CCF a small fluorescent tube about 2mm diameter the width of your display either at the very top or bottom of the screen. At times it can also be the inverter circuitry that powers up the said tube. One way is to run your PC and display as if nothing is wrong giving it a minute or soto finished booting everything. If looking closely you will notice semblance of your desktop albeit very faint, very dark or using a flashlight provide illumination to the display at an angle and the display is there, then chances are it is the backlight. Otherwise, it can be the input circuitry. Of course you have to open the monitor up and replace the defective component, More often than not no soldering required. Hope this gives you an idea or two. Lots of luck and pls post again how things turn up. If
Comment by Benimur, posted on Aug 10, 2007
Hi again zippie,
Ooooppppps, failed to notice the size 30, that would really require a good numbber of CCF (16). In any case, look for colder solder and/or discolored connectors male/female, both to and fro the inverted circuit(s), it is also a good idea to check the wires leading to the CCF themselves. Some brands/model are prone to arcing burnts causing terminal corrosion. Pls remember CCF works high freq, high volt. Past experience CCF connectors more prone to burnt than the inverter. And if it is the inverter, chances are and hopefully that it's just a cold solder which should be very visible. It seems you're in the right track, cheers.
Ooooppppps, failed to notice the size 30, that would really require a good numbber of CCF (16). In any case, look for colder solder and/or discolored connectors male/female, both to and fro the inverted circuit(s), it is also a good idea to check the wires leading to the CCF themselves. Some brands/model are prone to arcing burnts causing terminal corrosion. Pls remember CCF works high freq, high volt. Past experience CCF connectors more prone to burnt than the inverter. And if it is the inverter, chances are and hopefully that it's just a cold solder which should be very visible. It seems you're in the right track, cheers.
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