BAUHN 65" 4K UHD LED LCD TV will not turn on

Thread Starter

madaboutears

Joined Sep 29, 2015
9
This TV just stopped working shortly after the 12 month warranty ran out. It will not turn on from the Remote or the Standby Switch. The Indicator does not show Red or Blue. I have removed the Power Supply Board and have checked as many of the components as possible but cannot find any of them defective. I am attaching a picture of the Power Supply. Does anyone have any experience with this make? I would like to know where (which connector and pin) to mimic the "turn on PS" signal in order to do more tests on it.
 

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Thread Starter

madaboutears

Joined Sep 29, 2015
9
You are so right! with the service data I would be able to find my way around so much easier. I have contacted the local service agents for the service manual but do not hold out much hope - no reply so far. I have scoured the Internet for data on the item and found that it was originally a Thompson SA design sold to the Chinese. No service manuals! If you have any suggestions of where to look I would be most grateful!
 

SLK001

Joined Nov 29, 2011
1,548
Your TV is no good - it is worthless - you need to toss it. I'll give you $40 and take it off your hands and properly dispose of it.

Forget about trying to get a service manual - they aren't released to the public any more by most companies. You most likely have a PS problem. Measure the voltages at the connectors at the edge of the PS. You need power to power the power supply turn on circuit.
 

Thread Starter

madaboutears

Joined Sep 29, 2015
9
Commercially-speaking you may be right, but for me this is a challenge. The TV is in mint condition, the pcbs are in new condition and show no signs of age, not even a sign of the usual dust! I am sure that someone will come up with some useful advice. I am in no hurry and work on the unit when I feel like a break from the everyday grind.
 

LFC78

Joined Jul 17, 2019
1
my power supply has blown on this TV, TV not working at all completely dead - can anyone of you help advise how you got your issue rectified please? What was the cost to get a power supply put in by the contractors? Thanks.....
 

Joe Blo

Joined Sep 23, 2020
2
my power supply has blown on this TV, TV not working at all completely dead - can anyone of you help advise how you got your issue rectified please? What was the cost to get a power supply put in by the contractors? Thanks.....
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 TV......it'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??
 
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