Precision 7750 - LCD apparently went bad

Question

I purchased a Dell Precision 7750 workstation laptop on eBay at a significant discount. The problem is the laptop was in Canada; and therefore abrogated the support agreement that comes with all Precision workstations. II recently retired, and wanted the best laptop money can buy without paying the price from Dell itself. In any case, I knew it was from Canada, and I still purchased anyway since, I've had various versions Precision laptops over the years, and never seem to have problems for at least 3 or 4 years.

This time was different. At least 6 months after purchase, the LCD started having problems, with the display going blank from time to time. Then, the display went out all together. The thing is, the external Display Port and HDMI still worked fine. So, my thought was the NVidea card was good. Nothing I tried from the operating system worked so, I assumed either the display cable, or the LCD itself went bad. I opened-up the case, and found the display cable connector was broken so, I ordered genuine Dell parts from another eBay vendor, and put them both in. Unfortunately, this did not resolve the problem - or did it, and I have to initialize the new LCD through the BIOS? Problem is, I can't get into the BIOS from the external display, without disconnecting the display cable (got this tip from another google search). The problem would seem to be obvious --> if I disconnect the cable and force the EUFI BIOS to display on my external monitor, the BIOS won't recognize the internal LCD to initialize it. Obviously, I'm assuming the new LCD must be initialized to work natively once the cable is reconnected. So, it would seem I have a catch-22 situation here. Has anyone been in this situation, and tried something I haven't done yet?

I tried to pay for support but, Dell won't even touch it. I tried the original vendor in Canada, and they won't help me either. Yeah, the laptop works but, I would prefer to use the LCD when I need to use the monitor for other purposes. Can anyone help me out here with another solution? For sure, I know the cable was bad but, it's possible the LCD was fine. I just wanted to save time, and bought both. I'd appreciate any help I can get.

Thanks, Mark

Mary G · Answer

Dell does not sell on marketplaces like Ebay. You bought a used computer from a private seller. It does not have a warranty. This is a user to user help forum.

MSGilch1960 · Answer

I understand that ... I'm not asking for help from Dell.  If I were, I'd have no need to come to this community forum.  I'm asking for help from another user who may have been in a similar situation.

ejn63 · Answer

Start by trying to access the LCD diagnostic -- hold the D key through powerup. You should see a series of screen self-tests start running. If you do not, the display is either faulty or incompatible. Your post is not specific as to whether the "genuine Dell parts from another eBay vendor" you ordered included the display panel or just the display cable. Neither do you explain what "found the display cable connector was broken" means -- is it the connector on the back of the screen, the mainboard, both? And unless the system had been subject to some physical damage, the connector should not have been broken -- unless that was the initial reason the system was cast off to EBay for sale in the first place.

MSGilch1960 · Answer

I appreciate your response ...

I get nothing from the LCD screen. I can see the Operating System if I can either the display port, or the HDMI external connectors. I cannot see the boot-up process at all from the external monitor unless - as I explained - I unplug the internal cable that runs from the motherboard to the display (cable). Actually, I don't know if this will work, I just read that it's possible the low level boot process will be forced to use the external connection if the motherboard doesn't sense the presence of the internal LCD. Since I didn't want to mess with this problem myself, I took at to a shop that supposedly specialized in laptops. For all I know, they broke the 40-pin cable. They are very flimsy, when I looked at it myself. For all I know, the cable was good before I brought to this shop, and they broke it when trying to remove the cable. As far as getting the proper parts: I am able to gather the PC's manufacturer list from DELL's Web site when I give them my Express Service Code, or Service Tag. I simply ordered the exact manufacturer's part number from the second eBay vendor. The laptop worked perfectly for at least 6 months. Even though I've had great luck with Precision laptops in the past (I'm typing this out on my old M7710), I'm not naïve enough to believe the LCD just went bad. That's why I order both the cable (it interfaces with the LCD and the camera), and the LCD itself. Since the thing boots up fine with no POST errors (stop at "F1 to continue), I would guess after replacing the aforementioned, I just need to initialize them within EUFI - I have no idea. I just can't see the BIOS screen to be able to get into it. When I hit F2, I believe the BIOS screen does come up ... I just can't see it. I believe this because, if I bypass BIOS and let it boot all the way up, I can see the Operating System UI - albeit, from the external monitor.

MSGilch1960 · Answer

UPDATE:  I went to iFixIt's community forum, and posted the same problem.  It turns out there is an 'On/Off: lead from the motherboard, that controls the backlit display.  I was told to go into a darkened room, and shine a flashlight at an angle to determine if in-fact the screen is simply missing the 'On' voltage.  In fact, I saw the logon screen!  I'm convinced this is my problem but, I'm not sure where to go from here.  I'm assuming although all M7750's may be similar, there may be different manufacture schematic's dependent on the exact model number of the motherboard.  Looking at the inventory list from DELL's Support page for the service tag, I can't make heads or tails where this information can be discerned.  I don't mind cracking the back open to look directly at the motherboard but, if I remember correctly, there is all kinds of what could be the model numbers.  Anyone have a clue what quadrant it would be in?

jamesco131 · Answer

On your way to cracking the back, you should have seen the 7 character Service Tag/11 charater Express Service Code label or printed directly (bottom chassis panel). Grab a magnifyer/cell phone, for viewing. Additionaly, Dell adds it into BIOS settings, when that is viewable.

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Precision 7750 - LCD apparently went bad

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