LG W2252TQ transformer

[paulstef]

Hi,

maybe somebody can help me with this. I got a W2252TQ monitor from someone whose backlight doesn't turn on. I was told somebody has already tried to repair it but had no success.

The monitor turns on very dim for about half a second and then goes black, when shining light on it I can see that it is just the backlight that is missing, the picture is there.

On the attached pictures you can see the transformer which is a QGAH02098. The transformer has apparently two output windings, there are cables connected to all four connectors that go inside the screen.

Now something strange. The transformer measured open on one output side. I took it out to see if the winding is visibly burned. The corresponding (open) output doesn't even have a coil (see picture)!!

Why would they connect cables to an output winding that doesn't exist?
The transformer has already been soldered and my guess is maybe that the person who tried to repair it put the wrong one in.

Can somebody with the schematic at hand tell me what's the correct transformer for that board or how many output windings it's supposed to have?

thanks for reading

[selldoor]

Re: LG W2252TQ transformer

I dont have time right now but board number is EADp-42F if you search for that you will find images and see what transformers they have.

Look for your transformer on lcdparts.net. click on buy it now (it doesnt )

My guess would be its a hard to find one and someone has taken it off to see if they could rewind it, failed and just put it back.

[paulstef]

Re: LG W2252TQ transformer

My guess would be its a hard to find one and someone has taken it off to see if they could rewind it, failed and just put it back.

Thanks for that info.

The transformer looks like new though. I also find easily some on ebay and amazon for 10 to 15 bucks.

I'm not particularly experienced with computer display repairs, do these transformers have in general two secondaries?

[Th3_uN1Qu3]

Re: LG W2252TQ transformer

The pins are there for mechanical reason, to hold the transformer firmly into place. It is possible that there was no winding there in the first place.

[paulstef]

Re: LG W2252TQ transformer

The transformer is being offered as a replacement for Samsung BN44 00264B.
Now, I did find the schematic for BN44 00264A. The transformer definitely has two secondaries.

I get the impression that the cheaper options we get over the internet are fake components. So the person that replaced the transformer bought one of these and put it in and it didn't work.

I don't see why any manufacturer would put in extra unused components (the cables) into a $200 product.

Maybe I open the display itself to see if the cables are indeed connected to something.

I still would appreciate if anyone has a schematic for that board or at least part of it, the part with the transformer.

Thanks

[selldoor]

Re: LG W2252TQ transformer

Well if your not going to follow advice?

I say again

Look for your transformer on lcdparts.net. click on buy it now (it doesnt )

It clearly does not have a second winding


Did you look for other boards as suggested

[paulstef]

Re: LG W2252TQ transformer

Well if your not going to follow advice?

I say again

Look for your transformer on lcdparts.net. click on buy it now (it doesnt )

It clearly does not have a second winding


Did you look for other boards as suggested

Ok, after some more research I've seen that the transformer is obviously not the right one. The board EADP-42AF uses the TMS93137CT. And this one has two secondaries. And the TMS93137CT is sold on ebay as the right one for the W2252.

So my guess is the person repairing it was confused and put the wrong transformer in. I'll order the TMS and see if it works.

Thanks for your input.

[selldoor]

Re: LG W2252TQ transformer

Correct - its this one
http://www.lcdparts.net/TransformerD...ProductID=3697

so we will have to wait now and see if that fixes it could be more than one problem.
Have you anything else you can test the bulbs on

[paulstef]

Re: LG W2252TQ transformer

Correct - its this one
http://www.lcdparts.net/TransformerD...ProductID=3697

so we will have to wait now and see if that fixes it could be more than one problem.
Have you anything else you can test the bulbs on

What exactly would I need? Several kHz of 1000V? I don't have that...
Or is there a simpler way?

[selldoor]

Re: LG W2252TQ transformer

What exactly would I need? Several kHz of 1000V? I don't have that...
Or is there a simpler way?

Hahahahaha you might have - its called "another monitor" one that works- you just sub one bulb for another. I think you can also get bulb testers from that
lcd place or ebay but the transformer may be just as cheap.

[paulstef]

Re: LG W2252TQ transformer

Hahahahaha you might have - its called "another monitor" one that works- you just sub one bulb for another. I think you can also get bulb testers from that
lcd place or ebay but the transformer may be just as cheap.

I have one other good monitor , not sure if I want to open it and risk doing any damage. I will wait for the transformer for now. Unless I find some other way to test the bulbs.

Thanks

[Davi.p]

Re: LG W2252TQ transformer

Hi, some ps boards are used for different monitors even with less inches so maybe that trasformer type is made also for boards/monitors with only 2 lamps (i know it's difficult.. 2 lamps are for 15 inches only maybe) with only 1 winding, so the part is wrong, if you want to test the lamps post here the label of the biggest ic under the board, i can try to read its datasheet to disable the protection and you can test each couple of lamps with the part of the onverter with the winding present (resolder the wrong one).

[paulstef]

Re: LG W2252TQ transformer

Hi, some ps boards are used for different monitors even with less inches so maybe that trasformer type is made also for boards/monitors with only 2 lamps (i know it's difficult.. 2 lamps are for 15 inches only maybe) with only 1 winding, so the part is wrong, if you want to test the lamps post here the label of the biggest ic under the board, i can try to read its datasheet to disable the protection and you can test each couple of lamps with the part of the onverter with the winding present (resolder the wrong one).

Thanks I'll have a look at it later. What is strange is that there are wires connected to the in-existent transformer winding. I think somebody tried to repair it and put the wrong one in...

[paulstef]

Re: LG W2252TQ transformer

Thanks I'll have a look at it later. What is strange is that there are wires connected to the in-existent transformer winding. I think somebody tried to repair it and put the wrong one in...

That`s what happened, I was right. Someone tried a repair and put the wrong transformer in. The monitor works with the transformer TMS93137CT.

Thanks

[selldoor]

Re: LG W2252TQ transformer

Well done - good fix - not seen anyone put a totally wrong transformer in before
well worked out.

[Behemot]

Re: LG W2252TQ transformer

Similar problem: backlight goes on for a brief moment, than of, few seconds, one and off again and than it stays the same. Customer tried two new transformers before he sent it to me so transformers are NOT the problem.

The board is from Delta as you can see, FAN7314 is the inverter controller. I got 3.3 V on enable pin.

Tested the blue output caps, they seem OK. There are some GP sHitanos and Samxon GF used as replacement for the original ones but I guess this should not be the source of the problem…or should it? Voltage seems fine, well, at least with the inverter off there is 21 V.

[cpt.charlie]

Re: LG W2252TQ transformer

Overconsuption maybe?

[Behemot]

Re: LG W2252TQ transformer

Should also add I've tried a pair of different lamps. It is possible though that there is one bad on each side and I have actually just replaced it Can test lamps in different panel to rule that out…

[Behemot]

Re: LG W2252TQ transformer

With different panel and 4 different lamps same problem so it's somewhere in the inverter itself.

[mauda]

Re: LG W2252TQ transformer

Behemot: I am having the same problem. New transformer and lamps, but the problem is still the same.
Did you find the solution?