Dead 31MU97-B monitor, power board OK.

This is called the 'jump start' method and I don't recommend to use this method. It sometimes works, but it can also destroy one of the video processors. This is explained in more detail in this video from Coppell TV Repair:

https://www.youtube.com/watch?v=o6jL2a_L...

Here is the link with comments: https://integer13.wordpress.com/2018/04/...

We had a power failure about a month ago. They next morning I could not turn on one of my LG 31MUY(&C-B monitors. I thought the electronics were fried. But then after looking at this page, I tried the hold the power button approach for 30 seconds, but that did nothing. Then I tried the blog approach above suggested by Andrei. Yes, it took about an hour to do, but you have no idea how happy I was when it turned on again -- without having to ship it, pay repair fees, buy a new monitor, or deal with LG's repair dept., which seems to be MIA during Corona. Thank you so much Andrei.

Thanks for the link. Really useful in getting the cabinet apart. Playing around with the U205 chip worked, only not the way the link described. The data sheet for the MX25L8006E memory IC stated that, following a HOLD operation (which could have happened during a random shutdown, say) "To re-start communication with chip, the HOLD# must be at high and CS# must be at low." Since the HOLD# pin read high, I pulled pin#1 CS# low through a 2K resistor to pin#4 ground. (The resistor was to protect from overcurrent if pin#1 was driven by a very low impedance source.) It seems to have done the trick. (BTW, the +V shown in the pictures is +19V, while the IC is powered with only +3.3V. Fortunately, the author was only pulling the SCLK pin high through a multimeter's input impedance of 10M ohm or so, as a much lower resistance could blow out the chip.)

I just did this 8/1/21... and having 30+ years electrionics experience was shocked and people putting meters between 19 Vdc and pins on chips. Chips signals are ground or zero for low and no higher than vcc when 1 or high... so in this case 3.3v when high.

My fix, I'm not 100% which did it.. but I think Cycling power while touching the pins is required. I first tried a 756 Ohm resister between Pins 1 & 4 ... then I tried taking Pin 6 High by touching pins 6 & 7 (shorting them... as pin 7 is already held high. and cycled power while I held the pins... the speaker beeped and the a few seconds later the screen lit up.

Not really certain which touch of the pins worked as I cycled power after teh second touch.... but for certain... I was a lot less likely to damage circutis by not touching anythign to 19Volts not matter what.

I have the same issue with my 31mu97 though I have not isolated the issue bto the eeprom. I'm debating if to send it in or not. How difficult was it to solder the new chip in place?

If the power supply is good is the eeprom the most likely culprit with this monitor?

tysm-

Is the link above from coppelltvrepair the whole replacement board?

Mark

Bumping this. Is the part the whole board to replace or just the chip?

The website says: "...offers the EEPROM IC containing the firmware for LG 31MU97-B main board 62882801 / 31MU97/LM41C / EAX66105904."

So it's just the chip. Also, $10 for a full main board would be pretty crazy.

Somehow I never saw email notifications for these comments, apologies.

I just had this same problem happen again. The "jumpstart" method wouldn't fix it again. So I ordered another eeprom chip and its working again.

The link above is just the chip... I think i ordered it from them again, but through ebay this time.

If you have a small'ish soldering iron and some tweasers, its not too hard to replace the chip. It's an 8 pin SOIC. The hardest part is getting the clamshell case apart with prying tools.

The monitor is currently with an electronics company – I've no practice pulling bezels apart, my multimeter hails from the late 1960's and it's decades since I wielded my soldering iron.

I imagine disconnecting the power board from the mainboard is what they did, though when I spoke to them they hadn't spotted the existence of the power light.

According to these people:

http://www.coppelltvrepair.com/p/1482/re...

a dead monitor can result from a problem with the mainboard. Certainly I'm wondering what conditions must be met for the power light to come on.

I sent my main board to Coppell TV repair and they found the fault quickly and fixed it. I don't see anything different about the board after the repair, but it works again. I purchased the service manual and tested the 19V power supply, and the four power supplies on the main board, all were OK before I sent it to Coppell.

My Husband used LG software for ROM update.

Just turn monitor, use USB cable or Service RS232 cable connected to VGA.

Run update rom from LG database use monitor revision.

Power cycle. Reset settings. 10 minutes and no need send monitor to other countries.

How do you run an update from an LG database? Can you explain this in more detail?

Fennella,

Can you please provide more information?

I'd like to try to update the ROM prior to opening up my monitor.

After doing some searching on the internet I couldn't find an update file, can you tell us where you got this?

What computer software did you use to perform this update?

Thanks!

Danny

I can also flash the EEPROM of the LG 31MU97Z-B mainboard. This version of the mainboard contains a Thunderbolt port. Please contact me on https://www.monitorkapot.nl if you need help with this mainboard.

Hi everybody. I have the same problem - a dead LG 31MU97-B. Is there any way to try the eeprom update via thunderbolt or usb prior to opening up the whole thing? I just pried open a cheaper monitor and it’s a huge mess.

If I can avoid opening it or sending in the board. Any help is much appreciated!

Hi, would you have happened to have taken a firmware dump from one of these monitors as it seems to extremely difficult to track down the firmware.. to re-flash the eeprom... I have the hardware needed just can not find the file/bin/firmware i need.

You say "to hold the power button in for 30 seconds unplugged." Can you explain more in detail? I suppose you mean to keep the joystick at the bottom pressed for 30 sec when the monitor is not plugged in the socket? (did nothing for me so far, so I probably got it wrong).

Yes, that is the power button. It resets the stored efi. If that didn't work there is probably a hardware issue.

Tried this as well with an August 2016 date on the back of the monitor. No joy. Died after a 5 second power outage.

Our experience has been if the monitor loses power while it is on, there is a decent chance it will not come back on. Fix is to replace the eeprom.

So what is your question?

Use the eeprom programmer discussed in that wordpress.com posting. It costs $10 from Amazon. Much easier than resoldering. You could even pull the current firmware from the eeprom that you bought on ebay.

How were you able to open the back of your 34UC87C? All of the tutorials I have found online seem to be for different models with more of a clamshell design, whereas the 34UC87C has more overlap between the front and back panels. When I've tried to use a flathead screwdriver to pry what I assume are clips, I've seen no movement at all and have actually cracked the front cover mildly.

Did you check your power supply? These modules can become faulty too.

I didn't because the screen went black when I was browsing through the service menu and I felt like this was the root cause of the problem. It sounds like a good idea to check voltages though. Thanks for the suggestion, will do this later today and report back.

@monitorkapot

I get 19.17V from the power board.

@alfred3778 Ok, then the issue is on the mainboard. You could try to reflash the EEPROM once again. Maybe something went wrong in your last attempt.

@monitorkapot Thanks a lot for your time dealing with my LG's issue! I would have to desolder and resolder again since the clamp doesn't get good contact when the chip is soldered to the board. I had flashed the EEprom (using flashrom and the binary file available at github) which went well. It also ran a verify which stated the binary read from the chip was the same as the source file.

Do you know what selecting "NVRAM INIT" in the service menu would do? If there is no other way I certainly would be willing to try again with the EEprom. Thanks again!