Dead 31MU97-B monitor, power board OK.

Question

ディスプレイの修理

ビデオ出力付きのPC用ディスプレイ(もしくはモニター)の修理ガイド

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Robert Tucker @linuxguy

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投稿日: 2018年1月18日

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Dead 31MU97-B monitor, power board OK.

I switched my 31" LG 31MU97-B off at the wall power socket and when I switched it on again a few hours later it was dead. So, untouched between switching off and switching on.

Dead means absolutely dead – no power light, no sound to indicate it has switched on, no message about powering off in a few seconds to save energy, no sign of a backlight.

I have taken it to a PC repair shop and to an electronics company that deals with monitors (but more usually the industrial type) and both say no blown fuses, no bulging capacitors and that the power board is OK. The latter thinks the display panel itself is probably OK.

Since there is no power light, which is presumably low voltage, I'm thinking this must mean something is causing the power board to trip or shut down (almost instantly). Is it (almost) inevitably the mainboard or has someone any other suggestions? Would I be right to think the power board is capable of shutting down when feeding into a short or too high a load or demand from the mainboard?

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I have this same problem...unplugged to move the unit and when I plugged it back in, no go...nothing.

There is a local repair shop, but I have tools and knowledge to troubleshoot and would like to give it a once-over before taking it in on Monday. Does anyone have instructions for taking the back cover off...don't want to break any plastic!

TIA...

Tom

Tom さんによる2018年5月18日

A risky business that I did not attempt myself not having gained experience on cheaper equipment!

You can buy special little plastic levers – they seem to be often called spudgers – quite cheaply.

Coppell TV say they use a number of old plastic credit cards or others of the genre.

I've read of people using screwdrivers – maybe they succeeded without damaging the case, maybe they didn't!

Robert Tucker さんによる2018年5月19日

I want to take a moment to acknowledge CTR for providing exemplary customer service when the main board in my 31MU97-B failed recently.

Problem solved!!!

Thanks to a previous commenter, I contacted Coppell TV Repair. I had a surprisingly lengthy conversation with the owner who was extremely knowledgeable and gave me some tips on how to get the case apart so I could get the mainboard out and send in for repair. With his guidance, I was able to get the back cover off and remove the mainboard without damage to the case.

I shipped the mainboard out last Monday via Express Mail and the repaired board arrived today (Saturday) via the same method. Installed the board, tested it before putting the back cover back on, looked good, so I buttoned it back up and am now typing this note on the repaired display.

These guys are first class and know their stuff...highly recommended.

Tom さんによる2018年5月26日

In the UK, I took my monitor to Maggi Electronics Limited in Bolton (Greater Manchester) on 10 January 2018.

http://maggielectronics.co.uk

Their/my/our problem was getting a replacement mainboard. They contacted LG in the UK who directed them to Equinox in Tewkesbury. For whatever reason, they couldn't seem to get the board supplied by them,

In the meantime, I contacted LG USA and LG in Korea. Both directed me back to the UK.

We were about to give up when I decided to write to Equinox to try to find out what their relationship to LG was (8 March 2018). A week later I had a new mainboard supplied by them. The following Monday, 19 March 2018, Maggi fitted the board free for me.

I don't know what the problem was with Equinox, whether they were worried about their relationship/contract with LG in the UK, whether my contacting LG in the USA and Korea created any response in the UK, but the moral of the story would appear to be that in the UK the first priority is to secure a replacement board.

Robert Tucker さんによる2018年5月27日

I have three of these set up on my editing computer. All working great for a couple of years. A few months ago I moved them over to be switched by the UPS and the the problems started. No lights and seeming no power. The power supply was working and making it available to the main board. I tried the jump start method and had success for one monitor. One monitor the screen black became split in the middle and one monitor will not respond.

looking for 3 new boards. Previously I had a friend in the US ship me a board with a new chip from Coppell TV and Repair but the board was broken in other ways.

or if I could find a true 4K monitor for less than 2k, with a huge color gamut and stabile with adjustments I should buy three new monitors.

Bear Lemley さんによる2020年7月14日

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Robert Tucker @linuxguy

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投稿日: 2018年5月13日

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The freight cost was too high to use the Coppell service. In the UK, I bought a new mainboard from:

https://www.equinox.co.uk

and monitor is working well again. Maybe I should put the old one on eBay to see if someone wants to buy it to see if they can repair it with a new eeprom,

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Sur ces moniteurs, il y a souvent des problèmes avec les alimentation (power) et il est judicieux de changer les condensateurs de filtrage, souvent des 1000 microfarads qui viennent de Chine. et ne sont pas fiables..

Yannzic さんによる2021年3月1日

On these monitors, there are often problems with the power supply and it is a good idea to change the filter capacitors, often 1000 microfarads which come from China. and are unreliable.

at the moment by Yannzic Edit

Yannzic さんによる2021年3月1日

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I have this same problem...unplugged to move the unit and when I plugged it back in, no go...nothing.

There is a local repair shop, but I have tools and knowledge to troubleshoot and would like to give it a once-over before taking it in on Monday. Does anyone have instructions for taking the back cover off...don't want to break any plastic!

TIA...

Tom — Tom
A risky business that I did not attempt myself not having gained experience on cheaper equipment!

You can buy special little plastic levers – they seem to be often called spudgers – quite cheaply.

Coppell TV say they use a number of old plastic credit cards or others of the genre.

I've read of people using screwdrivers – maybe they succeeded without damaging the case, maybe they didn't! — Robert Tucker
I want to take a moment to acknowledge CTR for providing exemplary customer service when the main board in my 31MU97-B failed recently.

Problem solved!!!

Thanks to a previous commenter, I contacted Coppell TV Repair. I had a surprisingly lengthy conversation with the owner who was extremely knowledgeable and gave me some tips on how to get the case apart so I could get the mainboard out and send in for repair. With his guidance, I was able to get the back cover off and remove the mainboard without damage to the case.

I shipped the mainboard out last Monday via Express Mail and the repaired board arrived today (Saturday) via the same method. Installed the board, tested it before putting the back cover back on, looked good, so I buttoned it back up and am now typing this note on the repaired display.

These guys are first class and know their stuff...highly recommended. — Tom
In the UK, I took my monitor to Maggi Electronics Limited in Bolton (Greater Manchester) on 10 January 2018.

http://maggielectronics.co.uk

Their/my/our problem was getting a replacement mainboard. They contacted LG in the UK who directed them to Equinox in Tewkesbury. For whatever reason, they couldn't seem to get the board supplied by them,

In the meantime, I contacted LG USA and LG in Korea. Both directed me back to the UK.

We were about to give up when I decided to write to Equinox to try to find out what their relationship to LG was (8 March 2018). A week later I had a new mainboard supplied by them. The following Monday, 19 March 2018, Maggi fitted the board free for me.

I don't know what the problem was with Equinox, whether they were worried about their relationship/contract with LG in the UK, whether my contacting LG in the USA and Korea created any response in the UK, but the moral of the story would appear to be that in the UK the first priority is to secure a replacement board. — Robert Tucker
I have three of these set up on my editing computer. All working great for a couple of years. A few months ago I moved them over to be switched by the UPS and the the problems started. No lights and seeming no power. The power supply was working and making it available to the main board. I tried the jump start method and had success for one monitor. One monitor the screen black became split in the middle and one monitor will not respond.

looking for 3 new boards. Previously I had a friend in the US ship me a board with a new chip from Coppell TV and Repair but the board was broken in other ways.

or if I could find a true 4K monitor for less than 2k, with a huge color gamut and stabile with adjustments I should buy three new monitors. — Bear Lemley
Sur ces moniteurs, il y a souvent des problèmes avec les alimentation (power) et il est judicieux de changer les condensateurs de filtrage, souvent des 1000 microfarads qui viennent de Chine. et ne sont pas fiables.. — Yannzic
On these monitors, there are often problems with the power supply and it is a good idea to change the filter capacitors, often 1000 microfarads which come from China. and are unreliable.

at the moment by Yannzic Edit — Yannzic

Oleg Gritsev @oleggritsev 評価: 95 2 1 · Answer 1 · 2018-10-15T18:53:40-07:00

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Oleg Gritsev @oleggritsev

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投稿日: 2018年10月15日

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I got my friend monitor LG 31MU97 with the same problem no power and LED light.

I just use PIN point test use service manual for LG 31MU97.

And i found what CPU stuck in boot loop with error report. So i just updated Firmware in ROM in IC205 (MX25L8006E) it have error checksum before. It is 1 Megabyte rom.

And after update everything works again.

I did it with two my friend monitors. It is common problem how i see.

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Where can you get the firmware?

Eddy Yau さんによる2018年10月18日

I got the firmware from LG monitor developers. I can provide it if you need.

You should have SPI chip programmer.

Oleg Gritsev さんによる2018年10月19日

Hello Oleg, did you reflash the firmware in circuit or did you desolder the serial flash?

And would you mind sending the firmware? How couls we get it?

thank you in advance

regards Uwe

uwe さんによる2019年3月2日

Oleg Gritsevc Can you provide the firmware?

Also, can you provide the information on how to program via the SPI program

Bob Brown さんによる2019年7月23日

Oleg Gritzev, I’ve discovered this problem on my LG 34UM94-P and having no luck getting the firmware from LG or anywhere else. Do you happen to have access to it and could send it to me? Thanks!

Sean Ziolko さんによる2019年8月9日

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Andrei Dobre @andreidobre 評価: 37 1 · Answer 2 · 2019-12-27T02:21:35-07:00

Andrei Dobre @andreidobre

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投稿日: 2019年12月27日

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I had this issue and came across this blog that helped fix it with a multimeter and an hour of my time. https://integer13.wordpress.com/2018/04/...

Hope this will help others too.

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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...

Erwin Aarnoudse さんによる2019年12月27日

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

Andrei Dobre さんによる2020年3月3日

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.

Carl さんによる2020年4月24日

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.)

Dietrich Seaman さんによる2021年5月27日

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.

Brian Walkowski さんによる2021年8月1日

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tysm @tysm 評価: 13 1 · Answer 3 · 2018-05-13T07:52:58-07:00

tysm @tysm

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投稿日: 2018年5月13日

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I had the same issue. 31MU97B Monitor died when the UPS was turned off while it was powered on. No lights would light up, nothing on the display. All the voltages looked good. No parts looked bad. So I bought the eeprom replacement from:

http://www.coppelltvrepair.com/p/1483/lg...

Swapped this out and I'm up and running again. Your mileage may vary.

It seems strange that a read only eeprom chip would die, so I was very skeptical to start with, but this did fix it.

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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?

brian wennersten さんによる2019年1月4日

tysm-

Is the link above from coppelltvrepair the whole replacement board?

Mark

Mark Janssen さんによる2020年5月15日

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

David さんによる2020年8月21日

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.

Jim Bob さんによる2021年1月20日

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.

tysm さんによる2021年2月26日

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Robert Tucker @linuxguy 評価: 109 5 2 · Answer 4 · 2020-12-21T10:19:44-07:00

So, my LG 31MU97-B has developed this problem again. I wonder if it is possible in this old thread to establish clearly the procedure to fix the most probable cause.

So, it’s the IC205 on the mainboard – quite easily found (once you can get to the mainboard – I’ve a spare one, of course). This chip is an MX25L8006EM2I-12G.

I buy a CH341A SPI Programmer with SOP8 clip.

Can I then follow this guide?

https://www.win-raid.com/t4287f16-GUIDE-...

I plug the programmer into a USB port and correctly connect the clip (connected to the programmer) to the EEPROM IC205 and issue on my Linux computer command line:

$ sudo flashrom --programmer ch341a_spi -r backup.bin

If I get no errors, I then issue the command:

$ sudo flashrom --programmer ch341a_spi -w lg31mu97.bin

having downloaded lg31mu97.bin from the link given in the WordPress blog:

http://aleksikoski.com/temp/lg31mu97.bin

Actually, I’m not too sure you’d be too advised to do this straight out. The CH341A would supply the EEPROM chip IC205 with the required supply voltage of 3.3V. However, the CH341A appears to operate at 5V and supply programming signals at around that voltage to the chip it is programming. It may therefore damage the chip we are trying to reprogram and other devices on the mainboard. Apparently, it’s possible to make the CH341A use the 3.3V supply at which it will still run. This solution involves wire and solder.

Got mine fixed again. Pete of Pete’s Computers (Manchester, UK) reprogrammed the IC205 chip for me.

http://peterscomputers.co.uk

Comments and advice very welcome, of course.

Peter Chubb @wom_bat 評価: 53 4 1 · Answer 5 · 2018-01-18T21:02:43-07:00

Peter Chubb @wom_bat

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If the power board is OK the power ON light should appear. If you disconnect the harness from power board to mainboard, are the voltages correct? There's a polyfuse in series with the mains input, it could have gone entirely.

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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.

Robert Tucker さんによる2018年1月19日

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.

goofy256 さんによる2018年5月14日

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Erwin Aarnoudse @monitorkapot 評価: 1 1 · Answer 6 · 2019-07-22T14:53:59-07:00

Erwin Aarnoudse @monitorkapot

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This problem is caused by bad software in an EEPROM chip on the mainboard (IC205) and can be repaired easily. If you flash an image of this software on this chip, your monitor will come back to life again. I did this repair for about 5 times and all attempts were successful.

If your LG 31MU97-B monitor is completely dead and you are not living in The Netherlands, please send your mainboard to me. I can fix this issue and send the mainboard back to you. If you live in The Netherlands, you can make an appointment via my website mentioned below.

Kind regards,

Erwin Aarnoudse

Monitorkapot.nl

The Netherlands

https://www.monitorkapot.nl

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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.

Fennella Shapiro さんによる2019年8月20日

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

Erwin Aarnoudse さんによる2019年10月2日

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

Danny Napoli さんによる2019年12月29日

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.

Erwin Aarnoudse さんによる2020年1月11日

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!

Patrick さんによる2022年5月8日

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[deleted] @deleted55974 評価: 1 2 · Answer 7 · 2019-08-19T15:43:00-07:00

[deleted] @deleted55974

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I know this is a pretty old post,, butI want to add my $.02.

I had 2 of these LG 31MU97-B’s sitting around for months from owners who hoped I could fix these. Both users gave up quickly, not wanting to spend more money on a problematic monitor. On an off chance that most things are simple I asked LG how to reset the board. Sitting around for months didn’t do it apparently. LG got back to me instructing me to hold the power button in for 30 seconds unplugged. Naw too easy and not logical. These were both dead as dead can be with not response. Boom! both started functioning perfectly again. What?? I’m still baffled.

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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.

hells さんによる2019年10月27日

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).

Dalibor Sevcik さんによる2020年3月26日

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

[deleted] さんによる2020年3月30日

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.

Markus Visnotius さんによる2020年4月2日

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hongas @hongas 評価: 1 2 · Answer 8 · 2020-05-29T22:49:53-07:00

hongas @hongas

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I have reset mine with guide with https://integer13.wordpress.com/2018/04/...

for awhile then all went back again after power out in my home area. :(

now trick with Amp meter does not work :(.

I have purchased replacement IC205 ROM from ebay but I do not have tools to do the board repair :(

My question is What do I need to do the replacement IC succesfully? what tools do I need?

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So what is your question?

Erwin Aarnoudse さんによる2020年5月30日

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.

Markus Visnotius さんによる2020年5月31日

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