HP L1908w Monitors go Black after 2 -10 mins

[DTLMG]

I have 6 of these monitors and they all have the same problem. They all have over 2000 backlight hours on them based on the on screen menu timer.

When the screen goes black, the power light stays green and I am able to see faint image on screen by shining it with a flash light.

I have disabled the on screen sleep mode and power saving mode via screen menu.

I believe I have isolated the problem to the inverter on all of them. Since the PSU and inverter are on the same board do you think recapping the board will help? All the caps look good. I dont have an ESR meter.

I have checked the backlights by using my CCFL tester made from a Case mod kit and the lamps stay lit (only able to check one at a time)

I plug the TEST CCFL from the mod kit into the inverter board and the light only lights half way up on two adapters and then goes out, on the other it lights up completely, but goes out in seconds.

I have googled and searched the heck out of this problem and have not found much. I do see the board is used on lots of other PSU as well, but in different configurations.

Any ideas on this problem?

[alexanna]

Re: HP L1908w Monitors go Black after 2 -10 mins

I plug the TEST CCFL from the mod kit into the inverter board and the light only lights half way up on two adapters and then goes out, on the other it lights up completely, but goes out in seconds.

When you are using your test CCFL dose the other connector for that coil have a CCFL installed in it?
If you are using just one CCFL at a time, 2 of the connectors lighting half way could be normal because of the way the circuit is designed.The other CCFL is required to complete the circuit.

[DTLMG]

Re: HP L1908w Monitors go Black after 2 -10 mins

Thanks for that tip... I am doing that right now...the mod light and all screen lights are working.... does this sound like a cap issue though? Its got me bedazzled

[alexanna]

Re: HP L1908w Monitors go Black after 2 -10 mins

Thanks for that tip... I am doing that right now...the mod light and all screen lights are working.... does this sound like a cap issue though? Its got me bedazzled

I would want to check some other things first

[trebo]

Re: HP L1908w Monitors go Black after 2 -10 mins

if your mod kit says one pair is working, then get one of the other monitors and find a good pair on that and plug them in with the other good pair
then run the monitor that has both good pairs connected to see if it stays on (hope you can understand that)
you could also resolder inverter transformers
even recap one board,nothing to lose six monitors to gain

[DTLMG]

Re: HP L1908w Monitors go Black after 2 -10 mins

After 5 minutes of the LCD screen being lit by 3 of the internal CCFL and the external CCFL test lamp i touched the PSU/Inverter and blew the fuse on board...

[alexanna]

Re: HP L1908w Monitors go Black after 2 -10 mins

After 5 minutes of the LCD screen being lit by 3 of the internal CCFL and the external CCFL test lamp i touched the PSU/Inverter and blew the fuse on board...

Did you ground something out?

[DTLMG]

Re: HP L1908w Monitors go Black after 2 -10 mins

Did you ground something out?

Im thinking so... Ill get another one set up here shortly So if I inderstand it correctly

I have 4 connectors on this PSU/Inverter board combo. To complete the circut I need to have my test CCFL plugged into one of the connecters, and another CCFL plugged into the other to complete that circut Or do i need to have all 4 plugged in? I am assuming two of the connectors are for the bottom CCFL and two are for the top.

[alexanna]

Re: HP L1908w Monitors go Black after 2 -10 mins

Im thinking so... Ill get another one set up here shortly So if I inderstand it correctly

I have 4 connectors on this PSU/Inverter board combo. To complete the circut I need to have my test CCFL plugged into one of the connecters, and another CCFL plugged into the other to complete that circut Or do i need to have all 4 plugged in? I am assuming two of the connectors are for the bottom CCFL and two are for the top.

I have been lucky enough to see quite a few of these monitors.
I will not say all have been CCFL issues, but the great majority has been.
The top pair of CCFLs has had problems with solder joints.
Even though you have tested the CCFLs with the MOD kit, I am going to recommend you do one more test.
Disassemble the monitors enough to get to the CCFL connectors.
Do not dissemble the panel, And the ribbon cable does not have to be installed.
Try using the bottom set of CCFLs of two panels, see if the 2 second problem goes away.
Please make sure everything is insulated so as not to touch ground, This includes the ribbon to the panels there is voltage on it.
Edit; even though your problem can take minuets to occur, I would still call it a 2 second problem.

[DTLMG]

Re: HP L1908w Monitors go Black after 2 -10 mins

Ummmmm I grabbed a screen from a LG monitor and it hasnt shut off....So would we say its the CCFL of the monitors?

[alexanna]

Re: HP L1908w Monitors go Black after 2 -10 mins

Ummmmm I grabbed a screen from a LG monitor and it hasnt shut off....So would we say its the CCFL of the monitors?

I would say so, look at the small return wires where they solder to the CCFL tubes.
If you notice any discoloration of the wiring near the silicone cap, you have found the problem.
Use something to lub the silicone end caps [silicone is great]and gently work the caps off try to avoid tearing, Make sure to strip enough wire back to get to good wiring if you see any oxidation on the wire you will need to go further back. Then re-solder and check your work before you fully assemble.

[retiredcaps]

Re: HP L1908w Monitors go Black after 2 -10 mins

Look for signs of these

http://s807.photobucket.com/albums/y...klight%20lamp/

[DTLMG]

Re: HP L1908w Monitors go Black after 2 -10 mins

I have been lucky enough to see quite a few of these monitors.
I will not say all have been CCFL issues, but the great majority has been.
The top pair of CCFLs has had problems with solder joints.
Even though you have tested the CCFLs with the MOD kit, I am going to recommend you do one more test.
Disassemble the monitors enough to get to the CCFL connectors.
Do not dissemble the panel, And the ribbon cable does not have to be installed.
Try using the bottom set of CCFLs of two panels, see if the 2 second problem goes away.
Please make sure everything is insulated so as not to touch ground, This includes the ribbon to the panels there is voltage on it.
Edit; even though your problem can take minuets to occur, I would still call it a 2 second problem.

Okay after dissassembling 50 or so monitors I have a better understanding of how they work and the test you asked me to perform. With the original top and bottom lights plugged into the inverter, the screen comes on and goes off within seconds. Using a known good CCFL in the inverter in place of the top panel lights, the monitor continues to operate normally. So tomorrow I will do as you have suggested and check the solder connections on the endcaps. I will post my findings. I will be very happy if I can get these 6 monitors fixed.

[DTLMG]

PROBLEM FIXED HP L1908w Monitors go Black after 2 -10 mins

I have been lucky enough to see quite a few of these monitors.
I will not say all have been CCFL issues, but the great majority has been.
The top pair of CCFLs has had problems with solder joints.
Edit; even though your problem can take minuets to occur, I would still call it a 2 second problem.

Alexanna: 1 down 5 to go, you were absolutely correct the solder joints are bad.

One question for ya...it took me a couple hrs to get the first one done, I had to completely disassemble the monitor to repair this solder joint, what is the easiest way to resoler this, in the light cradle or out of the cradle?

I did rip the silicone caps, and during diassembly put it back to gether with an automotive silocone. I read this somwhere.

If you lived closer we have a cold one to celebrate!

After repairing this monitor I had a "brainstorm" The recycler that let me disassemble the gaylord of monitors really wanted me to disassemble the front panels to remove the ccfls. I am going to revisit this idea as I will have plenty of spare CCFL's laying around ready to go!

Heres to ya my friend..

[PJL]

Re: HP L1908w Monitors go Black after 2 -10 mins

I have another example here with the poor solder joints. Pressing down on the end of the CCFL cures the problem. Anyone written any notes on dismantling as so far it has been a nightmare.

[robertcmg]

Re: HP L1908w Monitors go Black after 2 -10 mins

Hi I've got the same problem about the monitor going off and I'm not a teck diy wiz and I'm too afraid to do it myself and I was wondering if any of the people on here who have fixed the problem lives in the UK near Manchester preferably because id love if I could just post it to someone to get fixed

[int0x13]

Re: HP L1908w Monitors go Black after 2 -10 mins

I have another example here with the poor solder joints. Pressing down on the end of the CCFL cures the problem. Anyone written any notes on dismantling as so far it has been a nightmare.

Hey, if i have all understood well, the process of resoldering the bad joint between CCFL and their cable, you need to disassemble all the LCD panel from A to Z? There is no way to resolder it without disassemble all?

[budm]

Re: HP L1908w Monitors go Black after 2 -10 mins

Hey, if i have all understood well, the process of resoldering the bad joint between CCFL and their cable, you need to disassemble all the LCD panel from A to Z? There is no way to resolder it without disassemble all?

That is correct, there is no other way.
http://s807.photobucket.com/user/bud...?sort=3&page=1

[Yervasios]

Re: HP L1908w Monitors go Black after 2 -10 mins

hi everybody...this is my first post...nice to be here...I recently got two of this monitors HP L1908w, both with the same problem.... the light up normally... the picture shown looks normal.... but after 2-10 minutes lights off ... where do you think i should focus? ccfl lamps or inverters? i resoldered the inverters in case i had a bad soldering but nothing changed...
ps These monitors have been working for a long time (5 years for 8 h/day )