Help: my TFT display works for only 3 seconds each time at power up

Most of the time, it is both the backlights and the backlight supply that must be changed. It is best to change these parts together. Samsung may not sell the parts directly. They will refer you to one of their service centres to have the parts replaced.

If you can see something in the display by shining a light on it, this means the above recommendation should be able to fix the monitor.

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JANA _____

After that the screen becomes dark. The LCD seems to function as when I illuminate from the front, the content is fainthly visible.

I opened it up and the backlights switch off after 3 seconds. There are 2 backlight driver circuits (2 transformers, 1 for each lamp) on this board. In addition there are 2 IC's that probably manage brightness setting and power saving. One has a type number BIT3106.

I need advise on what could cause the problem. A schematic of this board or TFT monitor or a data sheet of the IC would be welcome as well.

Did anyone have the same problem with this model of computer screen? LABEL: "Model Name 153S S, Model code GY15LSHN/ILC, Color display unit Type N° GH15LS"

Thanks in advance,

Patrick

Thanks for your kind advise, Jana. I think that would be not worthwhile, I payed $ 50.00 just for a new mains adapter for this unit, now this new problem... I would like to override the control signal that switches the supply off. Patrick

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I did some more tests: I connected each lamp in turn to easch connector of the driver: Both double lamps are OK. One of the 2 drivers is not working.

The BIT3106 is a Dual CCFL driver by BIT (Beyond Innovation Technology). It has open lamp protection mode, that switches off after few seconds if no current flows trough 1 or both lamps. I found the datasheet here:

The BIT3106 drives 2 transistor bridges each composed of 2 part n° P348P I guess from Fairchild or Fujitsu? (there's an F-logo on the ic's) The CCFL board is identified with: "LIEN CHANG CO, U-2072 Rev: A02.

Any chance for a schematic diagram of this one? Thanks.

Patrick

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Little to no chance of getting a schematic for one of those. They are board level repair even at the factory authorized depot and block diagrams are all that is available.

Check for the obvious, like open fuses to one of the output stages, etc.

It is pretty common for the fuses to go open on the lamp inverters from stress and age.

DigiKey is about the only source for them, I use the time delay version of the fuses of .25amps greater what was in there and have no return problems.

Only now I saw the burn-marks on the insulation of the transformer, the secundary is interrupted. I plan to replace it with one that has the same primary inductance, and similar secundary resistance. I don't know secundary inductance of the defect transformer.

Patrick

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