Repair guides for displays (or monitors) for computers or other devices with video output.

141 Questions View all

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?

Answer this question I have this problem too

Is this a good question?

Score 3


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!




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!


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.


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

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.


Add a comment

2 Answers

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.

Was this answer helpful?

Score 0


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:

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.


Add a comment

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:

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.

Was this answer helpful?

Score 0


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

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,


Add a comment

Add your answer

Robert Tucker will be eternally grateful.
View Statistics:

Past 24 Hours: 2

Past 7 Days: 16

Past 30 Days: 108

All Time: 389