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[Strange] HDMI not (really) working with my LG 22MP56HQ Display

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Processor Intel Core i7-4790 3.6GHz
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Memory Mushkin Enhanced Redline Pro 8GB ( 2x4GB ) bus 2400 cas 10 - DDR3 Dual Channel
Video Card(s) Palit Nvidia GTX 970 JetStream 4GB ( 256 Bit ) DDR5
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Display(s) LG 22MP56HQ Full HD - AH-IPS LED LCD
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Hi everyone!

I am new to this forum and recently I've just built my new PC which included the LG 22MP56HQ Display (CLICKY LINK).

I had to plug it to my Z97 motherboard first (via D-SUB and powered by my i7's HD4600) because my graphics card was delayed for a week. The monitor works fine with my D-SUB cable but it does not recognize my HDMI output from the motherboard. I notice whenever I plug in my HDMI alone, the monitor's backlight is lit up (as if it recognizes something) but it only displays "Checking signal", then "D-SUB, no signal, entering power save mode shortly". I also tried pressing "Input" button to see if I could change to HDMI output manually but it didn't work (the monitor is claimed to automatically switch to the single input if recognized).

I tried to play around with the cables (HDMI and VGA) and it turned out that it recognized the HDMI's input only both cables are connected. Windows recognizes as two monitors when they are both connected like this AND I can change between outputs (D-SUB/HDMI) manually with the "Input" button. However, when I unplug VGA (leaving HDMI still plugged in) the monitor just went black, back to the situation before (that it doesn't the HDMI anymore even if it is on HDMI mode when both are connected). IMO it's just like it needs the D-SUB cable to give extra power to recognize and run HDMI. I also tried another laptop hooked up with my screen via the same cable and it still does not recognize the HDMI, while the cable works fine with the laptop to a TV.

A day later I brought my screen back to where I bought and they tested it. Using the exactly same cable I brought alongside, the monitor works like a charm with a random ATi card that they were also testing (only HDMI connected, working on HDMI input mode). The only difference here (besides different VGA/mainboard combo) is that I forgot to bring my power cable so they used another power cable from other LG's monitor instead. So I thought the problem might come from my mainboard's HDMI port, not from the cable nor the monitor so I did not ask for swapping for a new one. I came home with the monitor and I waited my graphics card to arrive.

Finally my GTX970 arrived and I had the chance to test my HDMI cable. The card only provides miniHDMI so i bought a HDMI-to-miniHDMI cable, hoping it would work with the monitor and the card. Then I tried, and the monitor stil does not recognizes my HDMI input. This time it doesn't even recognize HDMI when I plug everything in. I tried a last attempt to install the driver from the disk provided with the monitor and it's still the same.

The reasons I need to use HDMI are for dual monitor (I have another old ACER LCD which supports D-SUB only), headphone/speaker parallel usage and I wanted to turn off on-board VGA since I can only use one monitor on each (my LG on GTX970 and my ACER on-board).
Has anyone encountered this problem before? Is this kind of problem so common that everyone just ignore the HDMI and go with the D-SUB instead as a temporary solution? I am really looking forward to your support and help (and sorry for my English).
 

Jota De Picas

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Hi! I know this is a really old thread, but I'm facing the EXACT same issue as you did. I have an LG 22MP55 with one DVI and one VGA port. I use the DVI with an HDMI adapter.
It is as you say, the HDMI only works if BOTH the VGA and the HDMI are connected together and to the same machine. It does not make any sense and it strikes me as a hardware bug....
Have you encountered what caused this problem or a solution?
Thanks in advance!
 

Mussels

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you're forgiven for thread bumping since its the same hardware :p

VGA isn't hotplug capable, so disconnecting it wont magically make the PC switch over to the HDMI.
Ideally, you'd want the VGA cable disconnected at the PC end *with the system off* and see if that helps.
 

Jota De Picas

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Wow, thanks a lot for such a quick reply!
Yes, I know what you mean and I've done that, but no, the scenario here is a little different. I plug only the HDMI, does not work just like OP said.
Then, I add the (redundant) VGA connection to the same machine: now HDMI works.
It doesn't make any sense to me, and also a Monitor should be a really trivial thing to use... I strongly feel this is a hardware bug by LG :(
 

Mussels

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Cooling Alphacool Apex UV - Alphacool Eisblock XPX Aurora + EK Quantum ARGB 3090 w/ active backplate
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Benchmark Scores Nyooom.
Could be, since its not behaving like it should.
 
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