LCD monitor transformer dead? Which one as replacement?

Thread Starter

Philipp “Ron” Oberdiek

Joined Mar 30, 2018
Hi everyone,

I am new to this community, so thank you for letting me join and also for any help in advance. :)
My knowledge in electronics is limited, but last year I build my first 3D printer and I did learn a lot. This thread, as in the title, is about my old lcd monitor, which is an Hyundai W220S. Directly after switching it on, the backlight switches off. You can however see from very close all the windows, which means the logic board is ok, I also ruled out the backlight itself, since it is powering on the first two seconds. So I thought the power board needs some repair and I started by replacing the capacitors, pretty cheap and worth a try, but this didn't solve the problem. So I tested some components on the boards and I stopped at the transformer for the backlight.
It has one primary coil and two secondary coils for the backlight, as marked by the red circles in the first picture. I removed it from the board and measured a resistance of 0.5 Ohm on the primary coil, 1.25k Ohm on the right secondary coil and 24k Ohm on the left secondary coil. I read somewhere, that the secondary coils should have the same resistance, so the transformer seems to be broken, am I right with this?
If so, I am thinking of replacing the transformer, but I have no idea of the specs of this one, it says "TMS93540CT B 08TM20 A", but I can't find any datasheets online, neither an exact replacement. I found this one on ebay (, which looks identical and has the same pinout, but has a different model number. My question would be in which way transformers are compatible, can I order on of the above and replace it with the old one?

Thank you for reading this and trying to help me. :)


Joined Jun 7, 2009
The board is typically supplied with power, grnd, and some sort of drive signal, which is often a dc reference. I would measure the reference signal to see if the board was being driven off, before digging too deep into the circuit. Look for a control IC and it’s specs to confirm it’s requirements.