Asus monitor turns on and off

[Venomus28]

Hello forum
I have an asus monitor who turns off right after 1 sec, i went to see whats going on and i found nothing unusual on the caps. then i found out some "burning" at the soldering points of the inverters
Pics below
Help

[CapLeaker]

Re: Asus monitor turns on and off

On the last 3 pics I just see excess flux. With alcohol and a toothbrush it will clean right off.

[stj]

Re: Asus monitor turns on and off

there are a number of joints that need to be resoldered, and i dont mean the ones with flux on them.

also the caps are crap (Elite brand!)

[mariushm]

Re: Asus monitor turns on and off

The problem is most likely located at the CFFL tubes in the LCD panel. Maybe one of the wires is loose (it got desoldered from the cffl tube due to excess heat) or maybe one of the cffl tubes is too old and uses too much current (normal as they age, the use more power) and the power supply stops itself to prevent overheating.

In order to inspect the cffl tubes, you'd have to be very careful opening up the lcd panel, it's made up of several layers of glass and plastic sheets and the lcd glass itself is very sensitive to pressure and can crack if you don't handle it properly.

Here's some pictures of CFFL tubes to get an idea of how they look inside the lcd panel : http://s807.photobucket.com/user/bud...?sort=3&page=1

[Venomus28]

Re: Asus monitor turns on and off

On the last 3 pics I just see excess flux. With alcohol and a toothbrush it will clean right off.

Yes i will do that for sure, but i think there is excess heat that caused that

[Venomus28]

Re: Asus monitor turns on and off

there are a number of joints that need to be resoldered, and i dont mean the ones with flux on them.

also the caps are crap (Elite brand!)

Can you point the ones you think to work on ?

[Venomus28]

Re: Asus monitor turns on and off

The problem is most likely located at the CFFL tubes in the LCD panel. Maybe one of the wires is loose (it got desoldered from the cffl tube due to excess heat) or maybe one of the cffl tubes is too old and uses too much current (normal as they age, the use more power) and the power supply stops itself to prevent overheating.

In order to inspect the cffl tubes, you'd have to be very careful opening up the lcd panel, it's made up of several layers of glass and plastic sheets and the lcd glass itself is very sensitive to pressure and can crack if you don't handle it properly.

Here's some pictures of CFFL tubes to get an idea of how they look inside the lcd panel : http://s807.photobucket.com/user/bud...?sort=3&page=1

Thats really an idea to start on
I'll do the inspection and i'll let you know

[Venomus28]

Re: Asus monitor turns on and off

I'll keep you posted, thanks friends

[Venomus28]

Re: Asus monitor turns on and off

Ive inspected the tubes and all looks ok ...

[Venomus28]

Re: Asus monitor turns on and off

So I've tested the tubes in another monitor and they work good.
Then tried the same monitor with the tube wires not connected and the monitor turned off again.
So I think the problem is the power supply.
What should I check ?

[Dumah Brazorf]

Re: Asus monitor turns on and off

Check the resistance of the transformer's coils.
You should remove them from the board.

[Venomus28]

Re: Asus monitor turns on and off

Grazie
I've measured the 2 transformers of the inverter and one of them doesnt shows signs or life at the part pointed in red lol
I'll take it out of the board and power it up and check if the monitor goes off again

[Venomus28]

Re: Asus monitor turns on and off

So I took out both transformers and powered up the monitor, same as before. Shut down itself.
What could be ?

[jondoe]

Re: Asus monitor turns on and off

Check Q803 Q802, the mosfet which feeds that transformer, compare the working side with the non working side.

[CapLeaker]

Re: Asus monitor turns on and off

and IC801

[Venomus28]

Re: Asus monitor turns on and off

Its not a backlight problem

[Venomus28]

Re: Asus monitor turns on and off

and IC801

Thank you i will

[CapLeaker]

Re: Asus monitor turns on and off

so do the backlights turn on only for a second or not at all?

[Venomus28]

Re: Asus monitor turns on and off

Yes, they turn on, when i plug the monitor on, for a couple of seconds then off