LG W2242S with burnt out inverter transformer

[oldmanhouse]

Hi all

I picked up a cheap LG LCD monitor (model W2242S) on eBay and was hoping it'd be a simple job of replacing some obviously faulty capacitors, but I think there's a little more to it than that.

The screen powers on for a couple of seconds, displays the LG logo and then the display turns off. The power LED stays on. The classic "2 seconds to black", I believe.

The problem (or at least part of the problem) seems to be the inverter transformer as it looks like it's got very hot and left burn marks on the PCB. I'm no expert, so was hoping someone might know what could have caused this, so when I replace it, I can ensure it doesn't happen again.

Any help would be greatly appreciated. I've attached some pictures of the board, and a close up of some possible problem areas? You'll notice I've de-soldered the transformer (I wanted to take a look at it separately), but I can always take pictures of it if anyone needs them.

Many thanks,

oldmanhouse

[Toasty]

Re: LG W2242S with burnt out inverter transformer

Discoloration can be simply from prolonged heat exposure of the board to the transformer. It does not necessarily mean the transformer is bad. Actually, the fact that it works at all sort of precludes a faulty trafo assumption.

The real culprit is likely those Su'scon caps.

Toast

[jetadm123]

Re: LG W2242S with burnt out inverter transformer

Since you already removed the inverter transformer, check it for shorts. With your meter set to 2K ohm resistance, measure across each of the secondary windings. You should read no more than 3% difference between the two.

[oldmanhouse]

Re: LG W2242S with burnt out inverter transformer

Thanks for the replies guys. I'll replace the caps as they're cheap, and will do some testing of the transformer itself

[selldoor]

Re: LG W2242S with burnt out inverter transformer

Hi - I did this some time ago with a w2042S replaced all the caps - made no difference. My transformer was an EEL22D******** and as I was not fully convinced from my testing ( difference was just about on the 3 % )that it was not the backlight bulbs didnt want to pay a lot for the a transformer. Left it for a while and eventually got one of these-http://www.ebay.co.uk/itm/Transformer-EEL-22-AIP0157-LG-L1719S-L1919S-/260738745349?pt=LH_DefaultDomain_0&hash=item3cb53d8405 which is a lot cheaper than others. It took the usual long wait from China but it works great.

[oldmanhouse]

Re: LG W2242S with burnt out inverter transformer

Thanks for the insight into how you solved your problem selldoor and thanks for the link - that's half the price of others I've seen on eBay.

I replaced all the electrolytic caps on my board with new Rubycon ones and it's made no difference. I've taken readings from the transformer (in circuit) but I'm not sure how to interpret them. They are as follows (multimeter set at 2000ohms):

1 & 2 - 1037
3 & 4 - 003
3 & 5 - ~005 (approx. as reading kept jumping about, and usually settled at a figure <10)
3 & 6 - < 010 (same as above. Reading was often different, but usually <10)
4 & 6 - < 010 (same again)
5 & 6 - 001

I took readings between each of the pins, but only the ones above gave a reading. I'm guessing this means something's popped inside?

I've attached pics for reference to show how my numbering convention correlates to each pin.

[selldoor]

Re: LG W2242S with burnt out inverter transformer

Hi - You have either missed measuring or missed posting the most important
7-8. In your picture the secondary windings are 1 to 2 and 7 to 8.
The others are primary windings and are not often at fault.
7 to 8 should be within 3% of 1 to 2 ie 1006 to 1068 ohms.
If not it is probably bust but always worth taking out and checking again.

[oldmanhouse]

Re: LG W2242S with burnt out inverter transformer

Ah I see, thanks for clearing that up. I wasn't sure which were the secondary and which were the primary, so I just measured them all.

I did take a reading for 7 - 8, but it's giving me nothing just like all the others not mentioned in my list above. Time to buy a new one?

[selldoor]

Re: LG W2242S with burnt out inverter transformer

Very Nearly,
It is worth taking it out and re-checking it. Just before you do that, I dont know where you were measuring but there is sometimes some lacquer or burnt flux on these pins so
try again (just for 7 to 8) making sure you have a good connection. Any I have come across have always had some ohms but if it has zero it may be worth getting a magnifying glass and checking the very very thin wire has not snapped off the pin - if it has it can be reconnected.

This means you have to be careful removing, which you have to be anyway:
Removing this is not easy, as at first none of it will want to move. You have to be careful not to bend the board too much especially as in this case the three ceramic caps 318-320 are very close to pins 3 and 5. Ceramics are quite brittle and do not like being bent.

As I recall I heated the transformer with a hairdrier and the underside of the board in that area just to stop the heat leaching away.

I then removed as much solder as I could from the pins using solder mop. I then started on most accessible pin and put a tiny watchmakers screwdriver in the gap between the board and the transformer then as I heated the pin pushed it in a bit lifting the transformer 0.5mm off the board. I then moved on to the next pin and repeated the procedure. Work around all the pins then with a thicker wedge go round again
Once you have a bit of a gap if you can move the pin slightly as it cools you can break the solder joint if lucky.

Give plenty of time its not a quick job - might want to tackle it in sessions.

[oldmanhouse]

Re: LG W2242S with burnt out inverter transformer

Excellent advice, thanks very much. I'll give it a go in the week when I've some time to dedicate to it.

[budm]

Re: LG W2242S with burnt out inverter transformer

I use thin stainless steel blade such as Exacto knife since the solder will not stick to it, to lift the pin up slightly when you slide it under the pin, main key is to take you time doing it.

[oldmanhouse]

Re: LG W2242S with burnt out inverter transformer

Update: bought a new transformer (one selldoor linked to), which arrived the other day. Fitted it and monitor is back up and running!

Many thanks to all for the help

[selldoor]

Re: LG W2242S with burnt out inverter transformer

Well Done! Not too long from china - great to hear it went well.

[lozzbo]

Re: LG W2242S with burnt out inverter transformer

Hi All,
I cant even call myself a newbie as I am completely ignorant of the technicalities involved.

I have a faulty LG2242S in a workshop at the moment and have been quoted £90 for the repair! During online research, I came across this haven of priceless information that may well save me a fair bit of money! The monitor normally lives in a recording studio, so any money saved on computer equipment would be spent in an area more specific to music technology.

My question is:
Other than the transformer in the Ebay link, will I also need to buy some sort of inverter circuit board, or is this part of the transformer purchase?

Sorry for my technical ignorance!

Cheers.

[selldoor]

Re: LG W2242S with burnt out inverter transformer

Hi If you have tested everything else and determined the fault is definitely
the transformer then that is all you need plus some soldering equipment.
Most members would recommend upgrading the caps on the power supply and the inverter board to prolong the life of the monitor.
Read this if you have not start at post19
https://www.badcaps.net/forum/showthread.php?t=10419

[Rtech]

Re: LG W2242S with burnt out inverter transformer

"My question is:
Other than the transformer in the Ebay link, will I also need to buy some sort of inverter circuit board, or is this part of the transformer purchase?"
Don't get confused,the board that the transformer is on is a Power Supply AND inverter Board combined.

[lozzbo]

Re: LG W2242S with burnt out inverter transformer

Hi,

Thank you so much for the excellent feedback.

Im going to order the transformer from the link right now!

Cheers.

[StevieBoy1912]

Re: LG W2242S with burnt out inverter transformer

Hi I have a lg w2242s and of course it's dead I have replaced all the caps with panasonic ones and the 470v at 100uf with a rubycon one and replaced the EEL22D transformer with the one from the link on this post but still nothing but my smps transformer in making a very loud clicking sound, the monitor powers on but not fully I was wondering if a smps transformer from a lg W1943SB would work or if anyone knows were I could get a replacement thanks.

Steve

[budm]

Re: LG W2242S with burnt out inverter transformer

I doubt that the SMPS transformer is bad, it is making clicking sound can be due to the fact that the circuit is in starup/shutdown cycle because it detects over current draw by the load. You have to use the same matching spec transformer.
Did you check the rectifier diodes, the power MOSFETS that drive the inverter transformer, etc?

[StevieBoy1912]

Re: LG W2242S with burnt out inverter transformer

hi I tested the rectifier diodes again to double check they are bouncing around from .1 to .5