Envision 17" LCD, another 2 seconds to black

[meanderer]

when I first got this one, the original owner says it has about 15 minutes of life before it goes black.... well here goes

I connected it to video source and play some video. after about 1 hour... poof, black screen with stuff showing thru with flashlight... now I turn it off and back on... it goes back off faster than the rosewill. it's now a "1 sec to black" problem.

I am waiting for the caps to come in so I didn't touch it for now.

But since I just got my CCFL tester working. I took it out and open it up and stuck them to the tester.

There was 4 CCFL connectors, I guess that means 4 CCFL tubes?

I plugged them with the LCD monitor off, so there's no image. All of them light up when plugged to the tester.

BUT, one of them are much dimmer than the others, it's as if there's a red tone to it.

Does that mean I found the offending CCFL? Is it normal to have a set of CCFL inside a monitor with different brightness (with the same power input)?
To test my theory, I left the dimmer CCFL disconnected and tried to turn the monitor on with just 3 of them connected. still 1 sec to black.

That's the progress so far.

At this point I am guessing the inverter board has problems, similar to the rosewill. Again, i am waiting on the caps.

[retiredcaps]

Re: Envision 17" LCD, another 2 seconds to black

when I first got this one, the original owner says it has about 15 minutes of life before it goes black.... well here goes

BUT, one of them are much dimmer than the others, it's as if there's a red tone to it.

Does that mean I found the offending CCFL? Is it normal to have a set of CCFL inside a monitor with different brightness (with the same power input)?
To test my theory, I left the dimmer CCFL disconnected and tried to turn the monitor on with just 3 of them connected. still 1 sec to black.

I have a Benq monitor with the same 15/20 minute runtime and then black screen. If you turn on again, it goes 2 seconds to black. Leave alone to cool off and it would work again for 15/20 minutes and pattern repeats.

I then finally got 2 of the same monitors and swapped the power/inverter board into the other monitor and it worked. So the power/inverter board was good and I can conclude the problem lies with the CCFLs on the other monitor. I haven't taken the CCFLs out yet to inspect.

I believe a pink hue means that particular CCFL is close to end of life.

Running 3 out 4 CCFLs connected, depending on the design, may result in 2 seconds to black because the controller chip may see that CCFL as shorted and shut down the entire system as a safety precaution.

If you have a spare CCFL, you could substitute it for the "red hue" one. Alternatively, if you have another open monitor, drag it close enough so that the Envision CCFL cable can power one of the monitor's CCFL. That way, you don't have to remove any CCFLs. That is what I did to solve one problem. It took some creativity though!

Drag over the Rosewill?

[retiredcaps]

Re: Envision 17" LCD, another 2 seconds to black

BUT, one of them are much dimmer than the others, it's as if there's a red tone to it.

More talk about pink hue as a dying CCFL.

https://www.badcaps.net/forum/showpo...&postcount=179

https://www.badcaps.net/forum/showpo...9&postcount=40

[Dgtech]

Re: Envision 17" LCD, another 2 seconds to black

The only suggestion I might add is to hook the tester up to the CCFL's and monitor the current on all 4 lamps. After getting readings, both working and non working conditions, I'd swapp the connectors and then monitor current again. If the odd current follows the connector then it's got to be that lamp.

[meanderer]

Re: Envision 17" LCD, another 2 seconds to black

the caps are coming in tomorrow, as I mentioned I have limited workspace so I want to take the stuff and do everything together.

Suppose one of the CCFL is bad and I am reluctant to replace it. Can I solder a similar load (resister) across the connectors and leave it be? I know the screen will be dimmer than it used to be. But considering each lamp costs around $10 and the size of the monitor itself, it may not worth the trouble of getting a replacement.

Not to mention I don't know how to disassemble the LCD and take apart the CCFL tubes inside, if there's a guide on how to do it I want to take a look.

[PlainBill]

Re: Envision 17" LCD, another 2 seconds to black

the caps are coming in tomorrow, as I mentioned I have limited workspace so I want to take the stuff and do everything together.

Suppose one of the CCFL is bad and I am reluctant to replace it. Can I solder a similar load (resister) across the connectors and leave it be? I know the screen will be dimmer than it used to be. But considering each lamp costs around $10 and the size of the monitor itself, it may not worth the trouble of getting a replacement.

Not to mention I don't know how to disassemble the LCD and take apart the CCFL tubes inside, if there's a guide on how to do it I want to take a look.

First, on the diagnosis. Aging CCFLs draw more current. A common feature of the protection circuitry is shutting the inverter down if any CCFL draws an excessive amount of current. The fact that one CCFL is dimmer and has the reddish tint characteristic of an aging CCFL tends to confirm this.

You COULD use a resistor as a replacement for the CCFL, but then honesty would require you sell the monitor at a discount - probably for $15 less than an equivalent monitor without such a serious problem. Rather, leave it on the shelf until you come across an unrepairable monitor you can strip for a CCFL.

PlainBill

[meanderer]

Re: Envision 17" LCD, another 2 seconds to black

The caps came, so I took and rosewill and this envision together and try the CCFLs.
The defect is indeed in the CCFL. the third tube (marked with black in the connector in that pic) is totally dark now. I brought over the rosewill's CCFL and connected them to this inverter board. No more 2 seconds to black.

Then I got careless and tried to connect this board to the rosewill's LCD monitor. The board suddenly starts to smell something. I took it off immediately. I noticed that one of the foams from a circuit board has touched one of the heatsinks on this inverter board and made a burn mark on top of it. There are no other burn marks. The heatsink is on the right side bottom one, connected to one of those transistors.

I tried to put it back the way it is. Except instead of the dead CCFL, I cut off its connector and spliced it to one of those aftermarket computer mod light CCFLs. and connected it to that one instead of the dead one.

The board turns on and lights up for 2 seconds. After that it shuts off with no lights and no response from anything.

Did I fry the board? I can hear clicking sound about once every second coming from the yellow transformer on the right side when power is plugged in.

[retiredcaps]

Re: Envision 17" LCD, another 2 seconds to black

The defect is indeed in the CCFL. the third tube (marked with black in the connector in that pic) is totally dark now. I brought over the rosewill's CCFL and connected them to this inverter board. No more 2 seconds to black.

I tried to put it back the way it is. Except instead of the dead CCFL, I cut off its connector and spliced it to one of those aftermarket computer mod light CCFLs. and connected it to that one instead of the dead one.

If I read and understand this correctly, try going back to where you had the rosewill's CCFL on the envision where you had it working. This will verify that the board is not fried.

If that works, maybe recheck your splice job to make sure it is good.

[meanderer]

Re: Envision 17" LCD, another 2 seconds to black

yes it wasn't fried when I dragged the 2 panels together. But I did something afterward that caused some burning smell. Then 2 seconds to .... dead board on the envision.

The splice job was ok, the CCFL lights up when connected to power.

see attached, notice the black spot on the right side. I don't know how it burns though.... is the heatsink charged?

[pedro]

Re: Envision 17" LCD, another 2 seconds to black

yes it wasn't fried when I dragged the 2 panels together. But I did something afterward that caused some burning smell. Then 2 seconds to .... dead board on the envision.

The splice job was ok, the CCFL lights up when connected to power.

see attached, notice the black spot on the right side. I don't know how it burns though.... is the heatsink charged?

Yup. It's connected to the - end of the diode bridge.

[retiredcaps]

Re: Envision 17" LCD, another 2 seconds to black

I can hear clicking sound about once every second coming from the yellow transformer on the right side when power is plugged in.

I believe the ticking/clicking sound every 1 second is the SMPS trying to startup? See PlainBill's explanation at

https://www.badcaps.net/forum/showpo...3&postcount=13

If you want to fix this monitor, you may have to start back at step 1 and ignore everything before that and start with measuring the main filter cap and the secondary voltages to see what damage has been done.

[meanderer]

Re: Envision 17" LCD, another 2 seconds to black

between my day jobs and a hobby I found some time to get back to this guy.
The transistor with the heatsink burn on it Q901. I searched it and found it to be this guy http://www.datasheetdir.com/P8NK80ZFP+download

I took a multimeter to it. and got some measurements in ohms.
G - S is 636 or 1300
depending on which way you put the leads

G - D is OL

D - S is 630 one way and OL in another

is it good or shorted?

[retiredcaps]

Re: Envision 17" LCD, another 2 seconds to black

I took a multimeter to it. and got some measurements in ohms.
G - S is 636 or 1300
depending on which way you put the leads

G - D is OL

D - S is 630 one way and OL in another

is it good or shorted?

I would say they are good. If they measurements were lower than 100 ohms, I would suggest testing them out of circuit to be sure because the of the surrounding components or circuit design.

[hoadle]

Re: Envision 17" LCD, another 2 seconds to black

In you case the CCFL backlight bad need replace set mean 2 CCFL, but I'm will replace 4 CCFL on my LCD monitor
Not thing wrong on you board

Defective CCFL backlight may has the following symptom:
•Screen flashes on red/pink and goes off.
•Picture stays on in red and slowly be come normal.
•Picture flickering with dim display.
•Picture flickering on and off.

Retirecaps is right on you case

"I believe a pink hue means that particular CCFL is close to end of life.

Running 3 out 4 CCFLs connected, depending on the design, may result in 2 seconds to black because the controller chip may see that CCFL as shorted and shut down the entire system as a safety precaution."

Here the website for you new CCFL backlight

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

http://www.buy.com/retail/usersearch...me&display=col

[meanderer]

Re: Envision 17" LCD, another 2 seconds to black

it's been a while and I got back to repair this guy again...

It seems that not everyone has read the thread in its entirety and make the comment about the CCFL. Yes, it was a problem but I made a blunder while repairing and in the process also damaged something else.

I have some knowledge in chinese, so I bought a replacement power board from a refurbisher in China. And also some CCFL tubes along with it. It took about 3 weeks to arrive but total costed me less than $20 including shipping and customs.

I replaced the power board, but the problem was the same. No power, clicking sound. This time I also hear some static noise with the same rhythm as the clicking noise. I thought that could be a sound related problem so I disconnected the sound amplifier board.

Now I am back to the 2 seconds to black. I put the presumably fried power board back. Also 2 seconds to black. By elimination, it turns out that the problem was with the sound module.

I proceed to replace the CCFL inside the panel. I would say this is a very annoying job. However, it was manageable at desktop monitor sizes as opposed to tight clearances in laptop panels, whew.

After replacing the CCFL, the monitor now gives stable image, just no sound.

The sound module has a few caps and a amplifier chip. I found the chip number and looked up the datasheet. Then I used a multimeter and found that there is a short between left channel to ground. Makes absolutely no sense to have signal totally grounded for no reason. So I ordered a replacement chip from digikey.

2 days later I took the chip out and measured the continuity between L channel to ground on the chip. indeed L channel and ground is shorted internally. Tested the same on the replacement chip. No short. Tested the trace where L channel was supposed to be, no short to ground. By that it is confirmed that the chip was fried by my accident and caused an internal short. Replaced the chip and the caps. One of the replaced cap had a very small leak on the bottom, if I didn't remove the cap it would've gone unseen.

button it up and now I have a good monitor. too bad it was only 17".

Thanks for everyone's help on the forums, cheers!!

Now I have an extra power board... what can I do with it lol~~

[retiredcaps]

Re: Envision 17" LCD, another 2 seconds to black

2 days later I took the chip out and measured the continuity between L channel to ground on the chip. indeed L channel and ground is shorted internally. Tested the same on the replacement chip. No short. Tested the trace where L channel was supposed to be, no short to ground. By that it is confirmed that the chip was fried by my accident and caused an internal short. Replaced the chip and the caps. One of the replaced cap had a very small leak on the bottom, if I didn't remove the cap it would've gone unseen.

Good job on finding the shorted sound chip and bad cap on the bottom.