Bauhn 65" LED TV with a backlight issue, single thin black vertical line & flickering/unstable display

Thread Starter

Joe Blo

Joined Sep 23, 2020
Hi, i'm a newbie here and I responded (see below pic) to an old thread on this TV type where someone wanted help diagnosing a no power TV issue that they were having on their Bauhn 65" I now find myself with 'new' issues after fault-finding and fixing my original no standby light issue. Sorry in advance for the long spiel below, just trying to paint a picture..........If anyone can help me fault find why I have no power to my two LED backlight strings that would be much appreciated. I am hoping that the LED backlight supply simply will not show a supply voltage with no load, which was stopped due to 'open circuit' detected and that when I replace the 1 x burnt 3030 LED and plug the two 96v dc leads back in it will magically all be fixed??? Anyone know if this is likely, or is there a particular software jiggle needed?? Maybe the LED driver circuit is fried.....

Hi, I realize this is an old thread, however.........I too had the same issue. I don't like the idea of our 'throw-away society' so I decided to search the net for a few suggestions, came up with nothing so then decided to trouble shoot the power supply board myself. I have an electronics technician background working with PLC controlled mining/civil works trucks, not really an expert with small componentry. I have enough knowledge to be dangerous I suppose.....Anyway, I started by surfing a few handy tutorials on YouTube and found one or two

relating to the need for the power supply board to have 5v dc standby, this pin is usually marked as 'STBY' or 'SB' or some variation of this......which should be present with the TV plugged in and on at the wall socket (most TV's have a standby light--typically red, this turns typically green when activated 'on' with the remote)..

It goes without saying that when dealing with a power supply which has a 'Hot' & 'Cold' side, you need to be extremely cautious and if you do not have a good basic understanding of how to safely work with these voltages, forget about fixing this's just not worth it, especially as Aldi etc will likely have a new set for sale at a real cheap price any time soon.

That said, if like me, you are OK with the whole 'Electricity is a great slave, but a deadly master' thing & you like a challenge/have some spare time, this fault-finding will likely be both educational and fulfilling. So if you establish that you do indeed have standby voltage, when you press the remote, the main board should register this as a 12v dc supply to the pin typically marked as 'on' on the power supply board. signal to the power supply board first. This then 'wakes' the power supply board which then sends power back to the main board, LCD screen via main board as well as the LED driver circuitry on this Bauhn set.

I found that the T5A fast blow fuse had failed, a 105 (1Mohm) surface mount resistor (SMR) had failed on the backside of the board as well as a 103M (10 nF high pressure safety cap) small power capacitor (CB202 I think). I then traced further and found that the N-Channel Mosfet MDF13N50BTH under the heat sink closest to the choke and two large orange filter caps had also failed. I personally think that these sets are 'designed' to fail given enough heat/time on these components, a little fan and/or better heatsinking could probably help prevent this........just my 2 cents........

Anyways, I hope this helps somebody out there.......I fixed this and then promptly forgot to plug in the two little (top right in your pic) LED 94v dc plugs back in, I think the main board, or some other circuitry detected this as 'open circuit' and promptly stopped supply to the LEDs. There are 6 rows of 6 LEDs connected in series on both halves of the screen, I eventually plucked up the courage to open this baby all the way and found one 3030 LED had failed???? Not quite sure why, anyway, I will get around to fixing that issue when I have some more time. At least it powers up and and with a TV LED backlight tester I have proved everything works.......just need to trouble-shoot the two LED driver circuits next, anyone got any suggestions where to start this? Like what path does the supply take before and after the two green transformers??