Asus VE278Q BackLight

[nv13]

Hello all!,
This monitor was given to me in a state that the LCD image is functional however the backlight was dim and flickering. I tried turning up the brightness on the monitor OSD and the monitor backlight ceased to flicker or function from that point forward. Upon the restarting and subsequent restarts of the monitor it initially flashes quickly and goes out after a split second. It is not the 2 seconds to black as is popular with other monitors. That is not to say the end solution isn’t though. The power button stays blue and the image is still visible albeit with a flash light. Everything else appears functional as normal.

Here is a run-down of the things that I have done so far (Keep in mind, I am a moderate noob).

• I have looked for the obvious bulging bad caps. I have found none.
• I have looked for scorching on all the PCB’s. I have found none.
• I have checked for shorting out of the LED Backlight connections. I have found none.
• I have tried connecting the LED backlight strips one a time and in combination to see if the flickering was isolated to a specific short to no avail. I am not sure if there is a way to test with a CCFL bulb as these are LED’s and they are strips and do not appear to be simple wires that can be tapped into.
• I have not found a fuse as I do not know what to look for (not a blub fuse as I am used to).

I am in the process of attempting the voltage testing per the guide. Power Supply/Inverter Board? T-Con Board? I am not expecting the T-Con Board to be at fault but I could be wrong.
I have attached a few images. Please let me know if more information is needed.
Any advice would be much appreciated.
Thanks to all!

[nv13]

Re: Asus VE278Q BackLight

If anyone knows what or where I can begin testing the voltage on which boards that may steer me in the right direction. Is there a section of (R)esistors or (C)apacitors and I should isolate and begin with?

[nv13]

Re: Asus VE278Q BackLight

These are the caps that I have on the power supply/inverter board (this is the tan colored board correct?), assuming it is at fault here. I was unable to test voltages, not entirely sure what I should be done to do so. I do have a multi-meter to test with. I have read that Caps need to be removed to test out of circuit unless using an ESR meter which I do not have. I have read the guides posted here about testing components. Not sure my multi-meter is reading correctly, more likely I am not doing it correctly.

(2) 1000uF 25v
(2) 470uF 35v
(1) 470uF 16v
(1) 100uF 50v
(1) 22uF 50v
(1) 4.7uF 100v

My questions is what caps should I use and or replace? I was thinking Rubycon but not sure what series and part numbers to get or does my issue reside elsewhere? ie not the power supply/inverter board or caps?
Thoughts anyone?

[selldoor]

Re: Asus VE278Q BackLight

Ok - with it all connected up test the voltages on the connector - bottom
right in Pic1 -has black and red wires. Start by setting your meter on 200VDC
Black probe on a ground screw and test each wire/pin on the socket.
If your probes are too fat put a pin or needle in alongside the wire and test to that. If it only reads leaa than 20v then change the scale on the meter for more accurate results.

Just for information the small red oblong box components are the fuses but they
seem ok as if not you wouldnt get anything.

I am not often on the forum at the moment - my Internet has a problem with external interference and as I can only download pictures very very slowly
I have given up. But I will try and look in to see how you are doing.

Which socket does the led lights lead plug into.(which pic is it on)

[nv13]

Re: Asus VE278Q BackLight

So I should hook everything back together and test voltages. Is this with or without power?
Thanks for pointing out the fuses.
The LED "ribbons" connect on "Pic 1" that small green board that is attached to the tan board. Or Pic number 3. Which is a closer image of the board. At the top of it there are 4 ribbon "flip" connectors. Like the type you might see on a laptop keyboard.

I will check voltages without power at this point. Unless otherwise noted to do so with power (plugged in).

[nv13]

Re: Asus VE278Q BackLight

Hey thanks for your input selldoor! I appreciate your time.
I am afraid in my haste that I have shorted out an item "C904" in Pic 1 as shown in "New Image 1" upload. I tried testing voltage without power and received no readings. Powered up and things came to an end fairly quick.

It no longer powers up however and I do not see any visual scorching or any other abnormalities from to this event.

I assume this whole power supply/inverter board is beyond saving. I have no idea anymore.

Again thanks for your help!

PS any one have a 715G2824-P02-010-001S that they can part with?

[Lumberjack777]

Re: Asus VE278Q BackLight

That capacitor is easy enough to replace. I suspect you took out the fuse with it. I think it's the red rectangular component in this last picture.

It depends on how much time and effort you want to put into this repair. And how soon you need this monitor.

I did find 2 of your boards on eBay.
1 is from the USA and more expensive.
2 is from China and cheaper (but it may take a few weeks to get there)
http://www.ebay.com/sch/i.html?_from...-001S&_sacat=0

[nv13]

Re: Asus VE278Q BackLight

Yea I was eyeballin that first one Lumberjack777.
I think the second one is different though... unless that green board can be swapped out as I have four LED input connections instead of one. I bet it would still work but would hate to chance it.

I am not in a hurry with this unit...it is more of a project than anything else.
The fuse might be the F901 T4V 250V. There happens to be three which I will probably just replace all of them. I may try to find non working monitors and see if I can use caps and fuses for parts as needed...

[Lumberjack777]

Re: Asus VE278Q BackLight

I'd make sure to get the board that looks exactly the same. You are right.

But......if I read correctly.....you'll still have that flicker problem. In my experience it is almost always a bad ccfl (lamp) or the inverter. The inverter is a separate board on your model. So it never was the power board to begin with.

You'll need the power board (or fix - check that fuse first)..... then move onto to the flicker issue. That will most likely be a ccfl, or the inverter.

[stj]

Re: Asus VE278Q BackLight

then move onto to the flicker issue. That will most likely be a ccfl, or the inverter.

it's an LED backlit monitor.

[Lumberjack777]

Re: Asus VE278Q BackLight

Oh I see. Duh. So what would he need to fix his flicker issue? Maybe you can help him. Thanks for clearing that up.

[stj]

Re: Asus VE278Q BackLight

probably need to start with foto's of the ribbons and invertor to work out how many strings of led's it has and what the drive chips are.

it's probably a bad led or 2, but first we need to work out how to get them to stay on for a visual inspection.

[selldoor]

Re: Asus VE278Q BackLight

Yes - I would say F901 has likely gone as the capacitor is on the primary side.
Not sure how you would short it out unless you put the board an a metal surface
while switched on? You need to be really careful as that BIG capacitor can carry 400volts!!

Anyway to test the fuse you need to get at the back of the board, set your meter on ohms 200 and test across the two legs of the fuse.
NO POWER TO THE BOARD ! Result should be the same as touching the probes together if it blown the meter will show the same as when the probes are apart.

Its an easy test so test the other fuses before replacing.

For test purposes the replacement fuse does not need to be the same type as long as it is the same voltage and rating.

There are quite a few posts on LEDs look at threads by budm at the beginning of the TV forum

[nv13]

Re: Asus VE278Q BackLight

Quick update...
I tested the F901 and it reads nothing where the other two fuses register a reading so I assume that those are good. I will need to replace only the one at this point.

As for the LED strips there are four that come off the power supply/inverter board. They identified as KOTL E220709 AWM 20798 80C 60V VW-1 Similar to this http://www.ebay.com/itm/KOTL-E220709...item3f3ecd15b2

Upon initial dis-assembly and inspection all cables appeared mint...however since this time one of the cables has been "altered" via children or pets... This should not have anything to do with the flickering as it was doing this before hand and was still doing it afterwards up until the blown fuse of course.

So my next question is do I disassemble the LCD panel? I have done this previously but I did not take pictures or anything as it looked a bit scary. I didn't want to damage or scratch something in the process however I can do this again if needed and snap photos.

Is the small green board that is attached to the brown power supply board the invertor board?

I have attached images of the board that is attached directly to the display itself that the LCD display panel ribbons are attached to as well as an LED back-light ribbon and end.

Hope this helps guys.

[selldoor]

Re: Asus VE278Q BackLight

Ok How you doing? replaced that fuse yet?
Are you back it flashing on for a second or 2

[nv13]

Re: Asus VE278Q BackLight

selldoor,
Sorry, I have no further progress at this point. I still need to locate a fuse for this board before I can move on. Was going to try a local Radio Shack store Monday to see if they had anything in stock before I go online, prices didn't appear that great upon initial search. I will keep you posted as I move along.
Thanks for checking in!