LG oled65b7v Repair

[Tony.T]

The TV starts but shuts down after 5 seconds. Do not see any picture at all.
Have measured all the power levels at supply board. Everything seems ok.  Motherboard seems ok as the optical output is on.
When disconnecting the T-con board the TV stays ON. But as soon i connect it again with motherboard it shuts down the power supplies after 5 seconds.

Measured the t-con board and all voltages seems to be present.  Also measured all the capacitances and no one is shorted.    Found a test point saying error detection, at the output to the motherboard. Probed it with oscilloscope and this test point is LOW but gets HIGH and 1 second after that the motherboard shuts down the power supply board.  As soon I disconnect the connector to the motherboard everything stays on. Of course as the motherboard does not get the High Error detection input. 

Then i started to probe all the test points where there is a voltage label.  Everything seems ok BUT except for two test points.  At the chip 0A=4D J1H  , cant find what kind of IC this is?   At the two test points labelled 1.1V_PG and 2.5V_PG it is 5V.  !!!   

The led on the TV blinks 2 times. Could not find the error code explanation either. This is the only thing I noticed to be strange.  If i can get the datasheet for this IC it might be easier to understand this strange thing.

is there anything else you can help me with?  Any tip how to continue testing? What points to test and is there anybody out there that have had the same issue with this board and have some info how to proceed? 

The easy way is to change this t-con board as it seems to be this because off ERROR DETECTION set high.  But is the risk that the panel itself is the problem and the T-con just says the correct thing? The owner said that the TV just stopped working one day. No cracked panel etc.

Have attached pictures of the board and one of them i have marked the error detection test point and also the voltages that are 5V besides the chip i do not know what it is.

Have not that much experience with fixing TV:s, mostly SMPS and laptops. 

Any help would be appreciated...

Thanks in advance....

[Tony.T]

More pictures...

[Tony.T]

closeup.

Download them and zoom in....

Specially the first picture as i have marked the test points in red...

[fzabkar]

There are several candidates for your "0A=" chip, depending on the package:

http://www.smdmark.com/en-US/search/code?id=0a%3D

Here are some service manuals, but they don't appear to be useful:

http://www.jordansmanuals.com/Default.aspx?Brand=LG&Product=Televisions&Model=OLED65B7T%20(OLED65B7T-T.AAUYLJD)

http://www.jordansmanuals.com/Default.aspx?Brand=LG&Product=Televisions&Model=OLED65B7T%20(OLED65B7T-T.ANRYLH)

The 1.1V_PG and 2.5V_PG test points appear to be reporting whether the 1.1V (core) and 2.5V (I/O) processor supply voltages are up to spec (PG = power good). I expect that an output voltage of 5V is simply a logic level which corresponds to Power Good -- it would not be the actual supply voltage.

[Tony.T]

Hmm..started to test something. if the T-con board does not communicate to the motherboard eax67150604.

Started to check capacitors and found under some shield that i removed shorted capacitors just beside a coil.  injected some current 1V ...2A. to see if something got hot. NOTHING...
increased it to 1.3 and the large processor in the picture started to get warm...around 37 degrees.  But no capacitors.

Started to remove all the shorted capacitors as they were not that many.  But still shorted between coil and earth.  Removed the IC chip N1607023 and still shorted.

When i removed all the capacitors marked with red, there were no more components left that were indicated as shorted. BUT still when probing between the earth pad and supply pad where the capacitors was...it was still shorted.  I think that the CPU IC must be shorted somehow!!!!... .

Just to buy a new one i think....a motherboard.   

Any tips before i do that?  Thinking if someone has some input regarding this and if i am thinking wrongly...

Thanks...

[fzabkar]

Are you seeing a dead short? ARM cores typically have a static resistance of 100 ohms or less.

[Tony.T]

Well...yes.

It reads 0.35 Ohms....

But also shows 0.9 volts when turning on the board...at the coil besides the capacitors that are marked with red.

[Mario87]

At the two test points labelled 1.1V_PG and 2.5V_PG it is 5V.  !!!

Just for future reference on these, they will be Power Good (PG) signals just to indicate to the CPU or whatever is connected to those signals that 1.1V & 2.5V are present, so them reading 5V is not necessarily a problem.

[Damperhead]

I just faced the same kind problem The TV starts but shuts down after 4-5 seconds. Do not see any picture at all.


I started by investigating the T-Con board and found exactly the same "problem" that was explained here on the forum. 2 test points showed about 5 volts, although the legend text says something else. All voltages were fine. That's not the problem. Unfortunately, I found this thread after my own measurements.

I investigated the Main board and listened to it by ear and clearly heard one of the coil of the DC/DC converter making noise. This is exactly the same coil L2000, which was an issue in this thread. I measured the capacitors of the output end and their resistance was quite small, about 17 Ohm, and the reverse polarity was about 20 Ohm. The fault cannot be in the passive components. The measurement result was the same without the L2000 coil. The DC/DC converter is probably the Core voltage for the processor ~0.95V-1.2V (who knows?) It gives about 0.92V when it is on. The processor ASIC heats up strongly and the coil and DC/DC converter controller a little. My interpretation is that the processor is broken. This can be try to verify by investigating the IC8800 signals of the boot Flash, which are nicely available from the connections of the pull-up resistors. All other voltages seem to work correctly on the Main board.

As a curiosity, it should be mentioned that the voltages on the T-Con and Main board can be kept on by disconnecting the 2 High speed flat cables between the T-Con and the main board.

I would be very interested to hear if replacing the Mainboard helped with the problem? Spare parts seem to be still available, even though the TV is a 2018 model. However, an interesting investigation behind which cannot necessarily be calculated a monetary value.

Modified - some typos found.

[Tony.T]

Well...i bought a new motherboard.  Could not solve this one....
Had nothing with t-con to do at all...
After installing the new one it worked after a reset. Something needs to be initiated again as the new board did not work directly. Some kind of pairing occurs when doing a reset. Dont remember how i did but just google it.  And after that it started to work...

[Damperhead]

I actually measured a few signals from the boot flash. The signals didn't make sense so I assume the processor ASIC is dead. I also tried to measure the processor's oscillator on the board. It did give a 24 MHz frequency, but the voltage swing was surprisingly small. In my opinion, the oscillator should swing the whole logic level. The operation of the oscillator can be tried to be measured by replacing the series termination resistor.


I have to start considering the purchase of a new or used Main board. The prices seem to be around 100 Eur. I just have to decide if it's worth it. I still see risks here.

[Damperhead]

It seems that the 16 -bit microcontroller on the board (Renesas R5F100GEAFB#30) takes care of functions such as the remote control and push button triggers during stand by. Probably the MCU also communicates via the I2C interface to the T-Con Board. At least the I2C signal is visible and measurable on the front panel board (includes IR sensor, power led multi directional pushbutton). The DC/DC converter marked in the picture takes care of powering the MCU and it is always on. The MCU seems to take care of starting the other DC/DC converters. It would be quite interesting to find out the startup sequence and other functions from the MCU, but unfortunately I don't have suitable probes for the logic analyzer at the moment. Moreover, it may be very tedious.