Hp L1925 lcd monitor black screen

[Ropat]

Have a Hp L1925 lcd monitor that the green power led light comes on but the screen is black. Used a flashlight and can see the logo and windows start.

Wanted to get some input from the forum before I open up the monitor.
What to be looking for that caused this problem?


Any help will be appreciated. Will be taking photos of boards when I get it taken apart.

[PlainBill]

Re: Hp L1925 lcd monitor black screen

Have a Hp L1925 lcd monitor that the green power led light comes on but the screen is black. Used a flashlight and can see the logo and windows start.

Wanted to get some input from the forum before I open up the monitor.
What to be looking for that caused this problem?


Any help will be appreciated. Will be taking photos of boards when I get it taken apart.

Welcome to the Badcaps Forum. These are typical symptoms of a dead inverter. This can be anything from a blown fuse, shorted transistors, shorted transformers, etc. On many monitors the inverter is on the same board as the power supply.

The first thing to do is to open it up, remove the inner shield to take pictures of the inside of the monitor. Post them here. Include close ups of any suspicious areas.

PlainBill

[EGuevarae]

Re: Hp L1925 lcd monitor black screen

Welcome to the Badcaps Forum. These are typical symptoms of a dead inverter. This can be anything from a blown fuse, shorted transistors, shorted transformers, etc. On many monitors the inverter is on the same board as the power supply.

The first thing to do is to open it up, remove the inner shield to take pictures of the inside of the monitor. Post them here. Include close ups of any suspicious areas.

PlainBill

I second PlainBill. Post pictures and we can start from there.
And welcome to the forum.

[mats23]

Re: Hp L1925 lcd monitor black screen

I have the same monitor, stopped working all of a sudden. (shortly after i ran a software calibration test)

Unfortunatelly, I havent cheched with a flashlight to see it there is something there, but the symptoms are: black screen, led green acting like nothing happened. There is signal in video card(I was running dual view - both ports are fine). Power+ signal cord seem fine.

I have open the monitor: 100% taicon caps, except few(3) that my suspicion were replaced previously since I have bought it SH couple of years ago.

All capacitors look fine, none swallowed, none blown, none ballooned.

I have read https://www.badcaps.net/forum/showthread.php?t=6534 and mostly same symptoms as https://www.badcaps.net/forum/showthread.php?t=7013 , but suspect that the problem is on other board where the power cord comes is. I am about to replace 2 caps of 1000uF, 16v that have been previously replaced... maybe there is the problem.

my question is: is it probable that caps can be broken even you cannot see it physically? and how about the inverter how do i test that without a multimeter?

New to forum, nice to see you all!

[mats23]

Re: Hp L1925 lcd monitor black screen

The caps i was about to remove (previously changed) are Rubycon... changed my mind...

[selldoor]

Re: Hp L1925 lcd monitor black screen

Check that the rubycon caps are genuine not rubicon or rulycon. If in doubt post a picture.
You will really struggle to do any repair without a meter.

You cant tell by looking at a cap if its good and you cant really test them with
a multimeter - you would need and ESR meter.

Do you have any spare ccfl bulbs or an old lcd monitor or screen off a laptop.

[mats23]

Re: Hp L1925 lcd monitor black screen

yes, I have checked that they are genuine(seen the badcaps blacklist first)!

the answer is no, i do now have old lcd nor bulbs. The boards, all three do not present any burnt marks or signs of physical stress.

The breakdown happened in front of me, i haven`t sensed any burned smell. the monitor had a high pitch sound all the time before(couple of years). In fact, if I remember right the phone called just before this happened. it was just under the monitor... is it possible to have had any effect? i doubt it, cuz it was hanging there for many times without something happened.

Now I am whit the lcd cracked open and with 2 spare 1000uF 16v caps....
I will plug it in to check with a flashlight...

[mats23]

Re: Hp L1925 lcd monitor black screen

Ok, I have done it! It does function.... i have seen it reacting.. so it gets signal but there is no light...
It May be the back-light? should I change the two Rubycon unswallowen caps or check the backlight lamp?

[budm]

Re: Hp L1925 lcd monitor black screen

Old CFL around?
https://www.badcaps.net/forum/showthread.php?t=19987

It can be just burnt wires on the lamps.
http://s807.photobucket.com/albums/y...klight%20lamp/

[mats23]

Re: Hp L1925 lcd monitor black screen

OK... I`ve starded opening even more the lcd... got suck with this fine cross screws I do not hold for the moment.. will get to it and open even more... i hope it`s the lamp...or the burnt wire...


Thought about it... highly unprobable to be the lamps.... does not have 2 lamps?? if one is burnt.. then it sould be light only from one end... right?

still thinking about the rubycon caps...

[selldoor]

Re: Hp L1925 lcd monitor black screen

There is another test you can do that I dont think has been mentioned.
It is the secondary windings on the inverter transformers. I cant help much as there is no pictures of this. It could be on the power board either one or two big flat transformers.
You need to put your meter on ohms 2000 and measure the secondaries.

We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attach...1&d=1290283049

https://www.badcaps.net/forum/attach...7&d=1280167246

[budm]

Re: Hp L1925 lcd monitor black screen

If any one of the lamp is bad, the protection circuits will go into shutdown. Selldoor suggestion will be a good start.

[mats23]

Re: Hp L1925 lcd monitor black screen

Well thanks for the reply; I have managed to find the thin screwdriver...so I have unscrewed to a point I cannot go further thus.. it is impossible to get to the lamps.
Will do try to get some pictures posted!

I have reached a circuitry that looks perfectly clean with a chipset CHIMEI(irrelevant probably). From this further on I may need to open the 7 or 8+ clips frame for me to get a clear view of the lamps or what's inside.

will get a meter tomorrow and measure the inverter... must-it be done while the inverter is on the board or I have to get it out?

[budm]

Re: Hp L1925 lcd monitor black screen

Please show the picture of the transformers showing the top side of the board and the bottomside of the board so we can tell you which pins to use to check the transformer winding resistance, no power to the board.

[mats23]

Re: Hp L1925 lcd monitor black screen

Here are the pictures with the power board. sorry for the blury qual but that`s preeety much the best in fast manner.

[selldoor]

Re: Hp L1925 lcd monitor black screen

Pictures are almost useless. IF that white connector goes to the lamps then Power off, with a meter on 2000ohms test across the two purple circles and post result

[mats23]

Re: Hp L1925 lcd monitor black screen

On the white thing is says 0204A1207
040020511-01o1

i have tested.. and shows nothing... no reaction

[budm]

Re: Hp L1925 lcd monitor black screen

We need the picture of the inverter board, not the power supply board. That white connector is for the AC input.

[mats23]

Re: Hp L1925 lcd monitor black screen

Here is the inverter board.. hope this is the one.


the thing is that the display is functioning... in the sense that i have seen image forming there.. but the pixels lack light...

[budm]

Re: Hp L1925 lcd monitor black screen

That the picture of the logic/video processor board, the inverter board is the one on the right of the picture, you can see the the lamp connectors with White and pink wires.
There should be two transformers on that board and we need good clean pictures of both sides of the board, if the pictures are not in focus, we will not be able to see the pin outs of the inverter transformers.