HP 1940 - no backlighting

[g.b]

Hello,
have LCD HP 1940. Got out in it's backlight.
Power board: BenQ 48.L1G02.A01
Replaced Q808, Q809 on C5707, Q805 on FU9024N and PF801 125V/5A fuse (I had no counterpart here so when I put the glass fuse 250V/4A).
When the monitor, there is a backlight for about 2 seconds and stops working again.
What do you propose to make this work?

When replacing the fuse busted my pad of PCB. So I did this (IMG_20130719_164600.jpg ). I think it has no effect on the backlight.

[sabre504]

Re: HP 1940 - no backlighting

Try replacing the solder on the inverter transformer pins

[budm]

Re: HP 1940 - no backlighting

You can still have circuits problem or bad lamps, you will need test lamps to find out otherwise you can be spending lots of time trying to repair the circuits when the problem can be the lamp/lamps.
You van try other lamps from broken LCD panel or make two of these test lamps.
http://s807.photobucket.com/user/bud...?sort=3&page=1

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

[g.b]

Re: HP 1940 - no backlighting

Try replacing the solder on the inverter transformer pins

tomorrow will try

You can still have circuits problem or bad lamps, you will need test lamps to find out otherwise you can be spending lots of time trying to repair the circuits when the problem can be the lamp/lamps.
You van try other lamps from broken LCD panel or make two of these test lamps.
http://s807.photobucket.com/user/bud...?sort=3&page=1

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

I have two CCFL lamps of disassembly. Do I need to check it to connect all four?

[budm]

Re: HP 1940 - no backlighting

You can do 1 pair of the one in the panel, and another pair of test lamps to find out which pair is bad, basically all 4 lamps will be used: 2 inside the panel, 2 test lamps. if the first test the screen does not stay on, then you use the other 2 on the panel to see if it will stay on. I myself when I work on monitor that black out after 2 seconds, I use 4 test lamp to see if they will stay on, that way I know the inverter/power supply board is OK.

[g.b]

Re: HP 1940 - no backlighting

Corrected soldering on the transformer. Still the same.

I plugged the CCFL. Below the result.
2 second backlight (1pair)
http://www.youtube.com/watch?v=0Erg9G2Jkfo

no backlight (1pair)
http://www.youtube.com/watch?v=wtH6qkBmcVA

[Rtech]

Re: HP 1940 - no backlighting

You have to have BOTH sets plugged in, if you only have one, then it will switch off anyway !!! so you need test lamps on one pair and originals in the other, then swap over

[budm]

Re: HP 1940 - no backlighting

Rtech, thanks for clarifying my instruction, I was not sure if he understood what I waas trying to say.

[g.b]

Re: HP 1940 - no backlighting

I connected the two pairs of CCFL. The effect is the same. The backlight lights up for a moment only a first line (shown in photo). The second line there is no backlight.

[budm]

Re: HP 1940 - no backlighting

"Replaced Q808, Q809 on C5707, Q805 on FU9024N" so those transistors are in the section that dose not light up the lamps, I cannot read the designators of the part from the pictures.
Did you also re-solder all the connections of all the transformers in that area?

[lexwalker]

Re: HP 1940 - no backlighting

have LCD HP 1940. Got out in it's backlight.
Power board: BenQ 48.L1G02.A01
Replaced Q808, Q809 on C5707, Q805 on FU9024N and PF801 125V/5A fuse (I had no counterpart here so when I put the glass fuse 250V/4A).
When the monitor, there is a backlight for about 2 seconds and stops working again.
What do you propose to make this work?

When replacing the fuse busted my pad of PCB. So I did this (IMG_20130719_164600.jpg ). I think it has no effect on the backlight.

I connected the two pairs of CCFL. The effect is the same. The backlight lights up for a moment only a first line (shown in photo). The second line there is no backlight.

My suspicion is bad transformer. Have you measured the transformers on the side where there is no backlight?