BENQ et-0027-b

[terminatorX]

Long time no see

Ok so this screen has the problem of some temporary flashing.
When PC is started with this screen it shows bootsplash screen and then the windows logo and then nothing, just a black screen. It seems that it has some problems maintaining the picture. Any suggestions?

[Rtech]

Re: BENQ et-0027-b

Open it up and sort some photos out, and I'm sure you will get some help

[bibilit]

Re: BENQ et-0027-b

Maybe not related, but have a look here:

https://www.badcaps.net/forum/showthread.php?t=14857

Benq/Dell monitors are known for those kind of trouble.

[ben7]

Re: BENQ et-0027-b

Tried the computer with another monitor?

Ifit works fine with another monitor, you have the "2 seconds to black" issue. (P.S. it isn't always two seconds LOL)

This can be caused by bad capacitors, a bad backlight inverter, or a bad ccfl/ccfl wiring.

[terminatorX]

Re: BENQ et-0027-b

Thanks everyone for your interest!

It would have been fun if the monitor would have c5707 transistors since I have some frome another troubleshooting project But thanks anyway bibilit.
I did try the monitor with another PC and still the same thing, however I had desktop light shining on the monitor and while it was black I could actually see that there is a picture. Which should mean that for some reason the backlight switches off. So I guess it's what ben7 suggests.
My pictures are not the best but should be enough for some multimeter testing perphaps.

[ben7]

Re: BENQ et-0027-b

Thanks everyone for your interest!

It would have been fun if the monitor would have c5707 transistors since I have some frome another troubleshooting project But thanks anyway bibilit.
I did try the monitor with another PC and still the same thing, however I had desktop light shining on the monitor and while it was black I could actually see that there is a picture. Which should mean that for some reason the backlight switches off. So I guess it's what ben7 suggests.
My pictures are not the best but should be enough for some multimeter testing perphaps.

First, check for some bad solder joints on the PSU.

Second, try measuring the voltage across any one of the capacitors C701, C702, C703, and C801 (they are in parallel). I'm not sure what voltage you should get, but backlight inverters usually use 24V. It may be anywhere from 12-24V. The thing we are looking for here is, once the backlights go off, does the voltage increase a lot? The backlight could be shutting off due to too low an input voltage.

Third, each backlight HV transformer has two secondary, high voltage windings. With the power supply OFF and un-plugged, measure and tell us the resistance of each winding. If you are not sure where to measure, I can draw a circle around each pin for you.

Have you done work on LCD power supply/backlight inverter boards before? Just be careful of the high voltage, don't stick your fingers on the board while it is plugged in!

-Ben

[budm]

Re: BENQ et-0027-b

Check the Inverter xformer's HV winding resistance.
It may have bad Dual-MOSFET also, there are four of them that drive the inverter transformers.

[terminatorX]

Re: BENQ et-0027-b

Hello!

Check the Inverter xformer's HV winding resistance.
It may have bad Dual-MOSFET also, there are four of them that drive the inverter transformers.

From the top down the reading on the resistance is as follows:
1. 2.1 MΩ
2. 0.991kΩ
3. 0.985kΩ
4. 0.982kΩ

First, check for some bad solder joints on the PSU.

Not totally sure what u mean..I guess u mean the whole board. Tried to look closely at the solder joints and lets say that alot of them look...not so nice but not broken. Have had a monitor that had a broken one. The pin just went through.

Second, try measuring the voltage across any one of the capacitors C701, C702, C703, and C801 (they are in parallel). I'm not sure what voltage you should get, but backlight inverters usually use 24V. It may be anywhere from 12-24V. The thing we are looking for here is, once the backlights go off, does the voltage increase a lot? The backlight could be shutting off due to too low an input voltage.

I think I have to ask for detailed drawings for the right points. BTW should the pc also be connected for this test or just the power?

Have you done work on LCD power supply/backlight inverter boards before? Just be careful of the high voltage, don't stick your fingers on the board while it is plugged in!

I did some trouble shooting on a monitor for more than a half year ago and maybe I came across some checking for that but I dont remember. Cant get enough of safety so thanks for that. But Im very green in this still so I cant get enough of details

[ben7]

Re: BENQ et-0027-b

Hello!
From the top down the reading on the resistance is as follows:
1. 2.1 MΩ
2. 0.991kΩ
3. 0.985kΩ
4. 0.982kΩ

That is the problem. One of the high voltage windings inside that transformer has burnt out.

[terminatorX]

Re: BENQ et-0027-b

Good!

Then we located the problem. I googled the numbers on the part without success...
What should I do?

[Rtech]

Re: BENQ et-0027-b

You could have a look at...... http://www.lcdparts.net/T.aspx
and see if they are on there !!

[terminatorX]

Re: BENQ et-0027-b

Like stated before Im green at this so don't assume anything.............

I looked quickly at the numbers presented at:
http://www.lcdparts.net/T.aspx.

Did not see anything that resembless what is wanted however if there would be someone kind that could verify this then the numbers can be seen in one of the photos.

Does anybody know what type of monitors are prone to have these exact parts?
Obviously asking this in case I find another monitor to act as donor.

[canadaboy25]

Re: BENQ et-0027-b

Could you post the part number(s)?

canadaboy25

[terminatorX]

Re: BENQ et-0027-b

Thanks for your interest canadaboy25! Thought people here would be more philantropic....

Anyway the supposed part number is on the attached picture. Hope it's distinguishable.

Would be interesting if the part could be obtainable from a different source other than

http://www.lcdparts.net/T.aspx.

Any decent suggestions are welcome

[Xer0]

Re: BENQ et-0027-b

Hi TerminatorX, I have the same monitor with the exact same problem. I have checked the transformers and get ~1k resistance across 3 of the secondary windings and an open circuit across one of them.

Did you have any luck finding the part?

the part number on the transformers is IJ.26061.021

This looks like it might do the trick: http://store.lcdparts.net/1J26051001-MS300T_p_2724.html

(More detail of the same part here: http://www.lcdparts.net/TransformerD...ProductID=2724 )

The description states that the secondary windings are around 950 ohms and the primaries are at around 0.5 ohms, my crappy meter isn't very accurate but this seems to be close to what I'm getting when testing the good transformer module. The pin configuration looks to match also, but without a dimensioned drawing it's hard to tell.

Can anyone please provide advice on whether this is an adequate replacement?

[TheAddler]

Re: BENQ et-0027-b

Would love to know if the above posted part worked or not. I have an Asus VK246H with the same board in it and was wondering if that transformer would work for a 1J.26061.021

Thanks!!

[thefox]

Re: BENQ et-0027-b

I havd a similar monitor, and I've deduced that one of the ccfl tubes being broken is the cause of the screen shutting down. Does anyone know where I can source a replacement ccfl tube assembly? I've stripped my whole monitor down but can't find parts online.

[Behemot]

Re: BENQ et-0027-b

Anybody got it working with the 1J.26051.001? The CCFLs itself can work fine from 650 to 800 V usually but some dramatic changes may shorten their lifespan. Question is if not only secondary but also primary windings count is the same, the ratio primary:secondary is important.

[Davi.p]

Re: BENQ et-0027-b

i don't imagine how can a secondary winding increase in resistance without going open...

[budm]

Re: BENQ et-0027-b

For example:
http://s807.photobucket.com/user/bud...?sort=3&page=1