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How can I (electronically) prevent an LCD monitor from going into standby mode due to lack of a video input signal? Answered

I have a dead LCD i want to turn into an artists light table.

Q:   How can I prevent the monitor from going into standby due to no input signal? In other words, I want to make the backlighting remain on without connection to a computer. 

It is a HP 24" widescreen that is able to be turned, tilted, and rotated in every direction over a wide range.  For this reason (and because I don't feel like building another box) I would like to use the existing enclosure and I have already disassembled and removed the actual LCD screen, leaving just the backlighting components. I am fairly well versed in electronics and I have tested points on the circuit boards in attempt to determine what input the circuit requires to NOT enter standby. There is a wiring harness from the LCD driver board to the inverter board with 14 wires which oddly enough, is actually labeled!  One terminal is labeled 'on/off' which I'm assuming would refer to the standby feature. This terminal measures +3.2v when the backlighting is on (not in suspend) and 0v when off (standby). I tried to jumper this to a spot on the board that is also 3.2 during standby to no avail.

Can anybody help???
Thanks!

Discussions

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ThirryH

25 days ago

Glad I found this post, even though it looks to be pretty old, since I am still not finding anything online.

I made one of these a few years back and now I am converting a bunch of old monitors my artist friends have brought me, but unlike my original project, seems like half of these monitors have this issue and there just aren't any answers or fixes when you look around online.

But the posts from zack247 and devicemodder got me started and then the post from orcsecurity brought me back to my original thinking that this should be somewhat akin to having a jumper on a PSU cable to allow it to be turned on without being plugged into the motherboard.

If you read the Wikipedia page that orcsecurity liked to, it seems that pins 13 and 14, the H-sync and V-sync pins, are responsible for this annoying little feature.

I am going to experiment with some VGA cables and adapters and dig deeper into the technical side of this and see if I can make an easy plug and play hardware solution. I will just have to see if this can be done by shorting the pins or if it would need a 5V signal.

If I succeed I will come back and update as well as whip up a quick instructable on how to make one.

Attached is a clipped section from the wikipedia page that gave me the idea as well as a pinout graphic I made that is much easier to read than the ones I have been finding online. All the pinouts are up to current standards.

Thanks guys!

VESA power on off.pngSTANDARD VGA PINOUTS.jpg
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zack247

8 years ago

i know that there is some sort of connection in the vga cable that sends the signal. perhaps a google search will help?(searches on google) here this might help

dsp3pinout3.jpg
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devicemodderzack247

Answer 2 years ago

That isn't vga...

This is VGA...

http://i.stack.imgur.com/DtrXl.gif

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frollard

8 years ago

I think you're on the right track seeking to trick the inverter into staying on. I bet at its heart its really a dumb circuit and just needs the on-off circuit told what to do. Can you get us a high quality picture of the board(s)?

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orksecurity

8 years ago

http://en.wikipedia.org/wiki/VESA_Display_Power_Management_Signaling

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clint taurus

8 years ago

Tricky? Definitely tricky. However logically it really shouldn't be, it SHOULD be quite simple... Probably one of those things so simple that I'm probably overlooking it, and when I figure out what it is it will probably just pi** me off for not having thought of it immediately! There HAS TO be a trick to it... I am not certain of this theory, but it stands to reason. My theory is as follows: There is probably some logic state, or voltage level (or lack thereof) which the monitor ... uh, monitors... to determine weather or not to enter the standby mode. So chances are there is a simple trick to it and the 'trick' is knowing what it wants to see! So, I've been looking at VGA pinouts and voltage levels and nothing really jumps out at me... But I have an idea!! It's a little complicated but it should work: Using parts I have already, and assembled in a linear fashion in this order: 1 male VGA connector (DB15) 2 dip-switches - 8 pole, single throw (for a total of 16 on/off switches 1 female VGA connector (DB15) Then wire pin 1 from the male DB15, through SW1 to pin 1 on the female DB15, and repeat for all 15 pins on either connector. Then the answer is as easy as flipping switches on/off! In essence this will enable me to connect or disconnect one wire (or more) at a time and therefore determine which wire(s) will bring the monitor out of standby! If anybody knows which wire i need PLEASE HELP!!!! Save me the headache!!! Thanks!

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Re-design

8 years ago

Wire the lights directly to the power source. Without having the set here I can't tell you exactly how to do that but with it on you might carefully measure the voltage and build a power supply for it to match. Or you could just replace the lights with some known voltage lights.

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lemonieRe-design

Answer 8 years ago


I'm with you on that, you'd probably only need to identify and modify the on/off circuit to do this. (Although that might be tricky)

L