hp 840 g4 need help with system hardware configuration

[hewlettpainful]

Hey guys I need some direction here, a recent upgrade is not going as smoothly as planned. So I got an 840 g4. It shipped with a matte HD panel that looked like trash. I replaced it with a complete glossy HD display assembly that is also a touchscreen. The new display assembly has an additional connector on the display cable, this connector mates to a previously unused female connector on my motherboard. The cable says something about LCD touch so I am thinking it's the correct cabling for touchscreen to my main board.

After connecting the new display the picture works perfectly fine, webcam is fine. There is no indication a touchscreen is present. No touch test in bios level hardware test. Nothing in windows. Tried a bios update, no joy. Triple checked the additional connector is seated. Seems good.

I've used cross reference sites to determine there are machines with the same motherboard part number equipped with touchscreens. On another forum I was told that what I'm after is a model number change, and not even all HP service techs can do that. Does anyone here have any insight on how to activate the touchscreen?


I've tried all the basics, adding windows drivers, using HP support platform etc. Apparently I voided the warranty. I bought this machine to upgrade it so I anticipated that anyways.

So I'm thinking my last hope may be to use the nbdmifit program to input a different model number or hardware configuration from a machine with a touchscreen, then reflash bios and it may work. Am I way off here? I'm happy with the new glossy screen, but I sure would be delighted if I could click links with my greasy mitts...

[mcplslg123]

Re: hp 840 g4 need help with system hardware configuration

Is schematic available?? Mb Code?? Some additional components may need to be installed to make touch screen work.There are mb's available with/without touchscreen options but they do have differences around edp and touch connector. So we need to findout those differences and that's possible if schematic is available.

[hewlettpainful]

Re: hp 840 g4 need help with system hardware configuration

I've been unable to find a schematic for this board unfortunately. The HP part number is
917503-001.

This page contains a cross reference of machines the board is installed in if you click towards the bottom of the page
http://partsurfer.hp.com/Search.aspx...ext=917503-001

Some of those machines are touchscreen models.

[hewlettpainful]

Re: hp 840 g4 need help with system hardware configuration

Here's something interesting I found when doing some more digging.

The mainboard info on my machine is missing when I look at system information. The first screenshot is my actual PC, note the mainboard info is not present. The second screenshot was borrowed from an ebay seller selling a 840 G4 touch, their mainboard info is populated. Could this be a problem or part of my solution?

[mcplslg123]

Re: hp 840 g4 need help with system hardware configuration

I dont think so. The mainboard info you are talking about is what we call DMI data. Missing dmi data has nothing to do with touch enable.Its all about some additional hardware components needed for touch screen enable option.

[hewlettpainful]

Re: hp 840 g4 need help with system hardware configuration

OK so lets look at this another way then. What if we needed to replace the mainboard for an 840 G4 touch? How would we know if that additional hardware for touchscreen is present if HP only sells one replacement board?

In the service manual there is mention of an LCD cable kit. It does not specify which screen it applies to so I think it may come with cables that cover all possible screen configurations. It's about 20usd so I think I will order it and see if there is anything included with it that differs from the wiring that came with my new screen.