[Carried over from original response in TEA thread]
These are a Korean made "Bottom rung" niche market monitor made specifically to leverage the mid-side LG IPS displays into the $350-450 market niche. LOTS of variables here in this market segment; you have to pay extra for a "zero dead pixels" guarantee, and as you've found out, manufacturer service is vaporware.
What you're describing is high probability to be either a video processor or switcher IC fault (mainboard) or a T-con board (usually attached directly to the panel, between the panel and the LVDS cable to the mainboard). The T-Con and the panel are USUALLY sold as a matched pair; as in the T-Con is designed and firmware-specific to the particular panel. In many cases, even different product runs of the same panel will require a differently calibrated T-Con.
Fortunately, as the T-con is produced this way, you MAY be able to find a generic part by the LG Part no that will work most of the time but may have inaccurate color reproduction; in many cases these are pretty cheap and well-worth taking a gamble on resurrecting your screen.
Some screens may have an LED Driver between the mainboard and T-Con; this processes the LVDS signal to control the LED backlighting zones for dynamic contrast. It is usually a go/no-go part, but can kill all picture to the screen as well.
[EDIT] Almost 100% certain now; dead T-Con board. You'll want to check the power rails to the T-Con and make sure they're within spec before you change it. If you can find one. [/EDIT]
mnem
Needs more cowchip.
This is just my opinion, but i think it's worth considering how far down the rabbit hole you want to go. It is definitely worth fixing, if it can be but the lead free solder, Korean origins and the magic mystery hour of problems would make me wonder.
That said will definitely be interesting to see what happens to it.
Have you seen this? http://nand-hate.com/2015/11/crossover-30q5-pro-black-30-2560-x-1600-korean-ips-monitor-repair-notes/ I have the same monitor and had a capacitor blow in the power supply just the other day. I actually posted about it in the "beginner" thread, because it was my first time posting and it seemed more appropriate.
https://www.eevblog.com/forum/beginners/am-i-in-the-right-place-power-supply-capacitor-replacement/
Good luck!
Since you have a pic that identifies all the main power rails, I'd start there with voltmeter and scope. Odds are a noisy/glitchy regulator killed the T-Con. I didn't realize this monitor was old enough to have CCFLs in it; once you get it fired up it may still not have proper color anyways as these high-brightness screens drive the CCFLs pretty hard and tend to fail by turning yellow then reddish.
Research a new T-con by the LG part number; you'll probably play hell finding it any other way.
Good hunting!
mnem
And Happy 2o18!
If there were tin whiskers, you should wash the board in ultrasonic bath, or maybe just with some cleaning chemical. Not heat it without having appropriate equipment.
https://www.aliexpress.com/item/free-shipping-original-for-LG-LM300WQ5-SDA1-6870C-0314B-logic-board/32759694802.html?spm=2114.search0104.3.13.zp2cUJ&ws_ab_test=searchweb0_0,searchweb201602_4_10152_10151_10065_10068_10344_10342_51102_10343_10340_10341_10084_10083_10307_10303_10302_10059_10314_10534_5790011_100031_10604_10103_10142,searchweb201603_40,ppcSwitch_7&algo_expid=c824583d-df22-4c1f-8525-fd388cc3199f-2&algo_pvid=c824583d-df22-4c1f-8525-fd388cc3199f&rmStoreLevelAB=5
https://www.aliexpress.com/item/LM300WQ5-SDA1-6870C-0314B-Logic-board/32825382638.html?spm=2114.search0104.3.7.zp2cUJ&ws_ab_test=searchweb0_0,searchweb201602_4_10152_10151_10065_10068_10344_10342_51102_10343_10340_10341_10084_10083_10307_10303_10302_10059_10314_10534_5790011_100031_10604_10103_10142,searchweb201603_40,ppcSwitch_7&algo_expid=c824583d-df22-4c1f-8525-fd388cc3199f-1&algo_pvid=c824583d-df22-4c1f-8525-fd388cc3199f&rmStoreLevelAB=5
Since you have a pic that identifies all the main power rails, I'd start there with voltmeter and scope. Odds are a noisy/glitchy regulator killed the T-Con. I didn't realize this monitor was old enough to have CCFLs in it; once you get it fired up it may still not have proper color anyways as these high-brightness screens drive the CCFLs pretty hard and tend to fail by turning yellow then reddish.
Research a new T-con by the LG part number; you'll probably play hell finding it any other way.
Good hunting!
mnem
And Happy 2o18!I have decided to start of with a total recap of the LVDS panel and the Inverter Panel, particularly as for the 30" screen requires 18V and yet there is 16V cap on that particular section.
It looks like there some of T-Con panels available but it does not look like the seller will send them to the UK or USA, other people are also apparently looking for the same panel and the general consensus is that maybe Apple have blocked it because they use the same LCD panel and T-Con panel and don't anyone breaking their strangle hold on the supply of parts? Seems possible as I heard many of unofficial apple repairers complain about will not allow them access to parts and schematics.
So far no success in locating a supplier of the LVDS panel should I need one of those.
30" LG panels never had a high failure rate. They had a lot of backlight bleed issues but not electronic failures. On the other hand, Samsung 30" panels of the same age had T-CON dying like cockroaches. They had Altera FPGA with the same BGA internal solder bump problem as NVIDIA GPUs.
Not likely any such evildoing on Apple's part; Apple wasn't able to stop LG from selling the original panels to your manufacturer in the first place. As I've said before; there's enough real evil in the world without listening to haters who invent more just to have something to bitch about.
mnem
No rest for the wicked.
Remember... the logic of large-scale manufacturing has NOTHING to do with the logic of ordinary, real people in the real world. These are ALL people with MBAs or WORSE. Their daily operation is built upon a level of BS that would make any normal, sane person gag.
mnem
No rest for the wicked.
Good idea re: recapping all the power supplies. Dirty power and lack of cooling are the primary cause of failures in the T-con and video compression processing boards, which it looks like are combined into one on this model. You might also want to stick some heat sinks on the outside of the tin plate right where the processors have thermal pads; every 8-10° you drop operating temp here doubles the life of the chip.
mnem
No rest for the wicked.
30" LG panels never had a high failure rate. They had a lot of backlight bleed issues but not electronic failures. On the other hand, Samsung 30" panels of the same age had T-CON dying like cockroaches. They had Altera FPGA with the same BGA internal solder bump problem as NVIDIA GPUs.
I can report that cockroaches have a very low fatality rate.
Turns out there are at least 2 sellers on AliExpress that sell these T-Con boards (new) at reasonable prices (thanks to wraper for the links) so if nothing doing after the recap (caps on order) I'll try one of those new boards, worth a try as the monitor has lots of good reviews under its other guises, Apple, Dell and I think HP.
Turns out there are at least 2 sellers on AliExpress that sell these T-Con boards (new) at reasonable prices (thanks to wraper for the links) so if nothing doing after the recap (caps on order) I'll try one of those new boards, worth a try as the monitor has lots of good reviews under its other guises, Apple, Dell and I think HP.There is nearly zero chance they are new. And basically zero chance you can get a new board, especially for such price. This LCD panel is around 7 years old, you cannot expect any new boards to be still available.
30" LG panels never had a high failure rate. They had a lot of backlight bleed issues but not electronic failures. On the other hand, Samsung 30" panels of the same age had T-CON dying like cockroaches. They had Altera FPGA with the same BGA internal solder bump problem as NVIDIA GPUs.
I can report that cockroaches have a very low fatality rate.I can report that you fail to observe fatality rate because they have high replication rate.
SNARRFFF!
You made me snort tea (not TEA) all over my keyboard. Fortunately, I learned the hard way and bought a washable one years ago.
While these particular panels may not be high-failure, t-cons in general are a common failure item, and these are connected to a video signal source and power supplies that were of cheapest design and as many corners cut as possible. Plus this one appears to incorporate the video compression processing as well, so even more points of failure concentrated in a single board.
Agreed unlikely these are new at that price, unless somebody bought a containerload of them at a dockside auction that were lost for a few years... I've seen much weirder occurrences.
Apple does require some stuff of their supply chain that seems over the top... until you realize that their entire ecosystem and customer service ethic revolves around steering the customer towards replacement rather than repairing product. This is a plus to those who can afford it; you walk in with your busted, you walk out with new as good or better than you had.
They don't consider the time you have to spend setting up the replacement unit to be part of the equation; you're supposed to just be happy with the "new wonderful". Besides, if you fully buy into their ecology, pretty much anything you bring them can be restored onto a new unit from backup and you lose at most a day or three of your i-Life.
Again; the true Apple customer are folks who consider time to be more precious than money, and Apple caters to that mentality... and in reality, there is something to that point of view.
I've long said that money exists for one purpose; to allow the greedy to set their own price on another man's most precious resource - time.
mnem
"Run, don't walk away from anyone who says 'Time is money.' They grossly undervalue your time, and they do so only so they can rob you of it." ~me
mnem
"Run, don't walk away from anyone who says 'Time is money.' They grossly undervalue your time, and they do so only so they can rob you of it." ~me
Turns out there are at least 2 sellers on AliExpress that sell these T-Con boards (new) at reasonable prices (thanks to wraper for the links) so if nothing doing after the recap (caps on order) I'll try one of those new boards, worth a try as the monitor has lots of good reviews under its other guises, Apple, Dell and I think HP.There is nearly zero chance they are new. And basically zero chance you can get a new board, especially for such price. This LCD panel is around 7 years old, you cannot expect any new boards to be still available.