E6420 Owner's Thread

I have problem with my E6420 since I started seeing blank screen after waking up from standby mode. After restarting it, nothing changes but all else works in laptop because I can see HDD activity, Windows sounds etc. After playing with LCD cable, RAM modules to no avail, resetting CMOS did help but until next restart and again until CMOS is resetted. BIOS this time did not show any video options whatsoever while previously I could change between Intel and nVidia using Optimus if I wanted as well. System information however showed Intel HD as video card which tells me the problem is with nVidia. Tried disabling various settings in BIOS to no avail. Even if I reset CMOS, do nothing to make it work with default factory settings or enter BIOS and save changes, next reboot I see blank screen. I also ran built-in screen test which showed LCD screen works fine.

Is this familiar to anyone here? Do you know of any way to disable discrete nVidia GPU outside of BIOS? Thanks.

 

Reads like a it may be a corrupt video driver initiation when Windows starts. However, confirm:

A. You do see the Dell splash screen and can get into the BIOS so there is video output, yes? (from what I remember, the E64XX series latitudes did not offer the option to enable/disable Optimus full time)

B. You can hit F12 and then manually choose to run the system diagnostics, yes?

C. Everything passes the diagnostics, yes?

Have you attempted to start the system in SAFE mode and watch to see if the issue starts when the video driver is loaded?

Have you attempted to reload a reference video driver direct from NVidia or an older Dell driver manually? Right or wrong, I do not like relying on driver update utilities. Simply because there is a new driver available, it doesn't mean it is better for your specific system. Likewise, even if the driver is good, if the utility does not remove ALL of the previous driver components, the installation of the new driver may not be 100% correct.

Have you reflashed the BIOS itself from within a DOS environment? You can make a Windows 98 boot disk on a USB flash drive that will boot you to a clean command prompt.

Have you removed and reseated the CPU itself (last resort)?

Scott-

 

Didn't think anyone would reply since my problem seems unique or at least one of a very few.

Okay, Scott. Let me clarify according to your points one-by-one:

Laptop never gets to that screen. It POSTS, stops since it warns me about default factory settings being restored, about 65W power supply because I need to use 90W (which is strange, since my laptop came with former) and it also offers me to press certain F keys to run diagnostic built-in test or continue with system boot. Whatever I do here, results in blank screen but BIOS loads, diagnostics load and OS loads. It's just that since that moment, my screen will be always blank until next CMOS battery takeout.

Yes this can be done only after taking out CMOS battery but it is until next BIOS saving changes, or even not saving and leaving factory defaults that screen will be blank after. I had Optimus options where I could default on integrated Intel GPU, default on nVidia GPU or set auto or something which will keep nVidia on idle until it detects application in Windows where acceleration is preferred.

I always had it set on nVidia so maybe if I had it on Optimus (auto) or at least integrated, I would be fine and work with operable video card but since BIOS does not allow to fallback on operating video card from malfunctioning, or does not factory default to operating video card, I can do nothing here. Integrated Intel video card works because I can access BIOS after taking out CMOS battery but after next restart or continuing after POST, screen gets blank until I take out CMOS again and so cycle continues.[/quote]

After taking out CMOS, at POST screen if I do anything whatsoever, I get blank screen and that includes running BIOS, Diagnostics etc.
But you may ask how I got into BIOS that I noticed Optimus option is missing and was able to tell Intel GPU works? Here's the thing. I after taking CMOS out, before I get to POST screen, I am able to access BIOS and diagnostics (this one requires pressing physical keys while laptop is off since in my situation it is the only way to run it) but it seems after system saves automatic factory defaults that laptop sets or I save changes in BIOS, that I since get blank screen either by continuing after first boot after I took CMOS or second boot which directly results in blank screen after powering system on.

Strangely, diagnostics showed no problem with graphic card. I don't know which it was testing exactly but I can tell that I saw strange line running from above to below screen. Maybe it was nVidia dead chip that Intel tried to show output through acting as controller? Here is link to video where you can see it: Running Line In BIOS Hardware Testing - YouTube

Cannot get to OS, see above.

I cannot access DOS due to blank screen but I did update BIOS long time before incident happened. It was upgrade from stock A04 to A08 version.

Doesn't removing CPU require application of thermal compound again? Anyway, I did remove CPU just to make sure I have PGA988B or PGA989 socket and that CPU can be transferred to replacement motherboard. Do you suggest me to take out CPU and see what I will get? Can laptop boot without CPU? I have high doubt CPU is the culprit.


Thanks.

 

OK, it looks like you have investigated just about everything and the main system board is suspect A.

With that said -

1. Have you tried connecting an external monitor before booting to see if that display also produces the same results?

2. Have you tried moving the notebook's display angle up and down before and during boot? Sometimes, this can isolate a bad LVDS cable with open or shorted leads.

Based on your video, the system seems to do OK displaying legacy graphics, but something fails when more than 16 colors are produced and/or when the refresh rate changes.

Scott-

 

Yes I did it through HDMI-out port to HDTV and nothing was displayed before boot and after boot. VGA-out I have not tried due to absence of cable and VGA monitor but I don't think there would be different result.

Tried moving display, tried reconnecting with LVDS cables (there are 1 big and 1 small) to no avail. The monitor works through built-in monitor only RGB test. All colors worked, brightness adjustment worked. In fact, after booting laptop, if I access BIOS provided it is all blank screen, I see how monitor changes its brightness. Same with after powering on laptop, when I see screen turns on. You can definitely tell screen works properly.

How do you know when more than 16 colors are produced? BIOS is 16 colors and video card test more than that?

By the way, if it is nVidia dead chip, then local computer laboratory who does repair on component level offered me repair which would equal to motherboard replacement on eBay including shipping outside of US and customs. I could take a chance because according to their words, I have nothing to lose in case of failed repair or their diagnostics but who knows what would happen later on, right? They want half for nVidia chip and half for their labor, though nVidia chip from China costs around $26-$35.

 

Based on your posted video, that line you see appears to be when the diagnostics tests the display by generating color variance rows and then a typical color bar before asking you if you see the colors. In this process, it should be testing up to 256 colors, but not 64K. Regardless, this is also where the screen may jump from 40Hz to 60Hz and that can be the trigger.

How much $$ are they asking for the repair and what country are you located in?

Scott-

 

For easier reference, I will specify prices in USD. I am in Israel and first repair lab asks $226 in total but when I asked about price for video chip by being curious, he refused to provide exact answer until I asked again and he told me it will be half the price. Another repair lab gave me range between $127-$269.

 

For that price, I would just replace the entire system board with a new/tested one.

Dell Latitude E6420 Motherboard NVIDIA GeForce GO7200T 54GVM 054GVM | eBay

Dell Latitude E6420 La 6592P Motherboard PH12P or H2YDF | eBay

If you need help with getting it purchased and forwarded to you overseas, let me know. If you also need a replacement dual channel LVDS cable, I have a few extra from my E6520 systems which use the same pinout.

Scott

 

What I did not mention is the hassle of sending my laptop to Dell's authorized service center in my country which took total of at least half day time investment forth and back rides to let them check laptop which I had to pay $65 for and another forth and back rides picking laptop back. The price quote for new Dell motherboard was $586, $85 for labor and $120 sales tax, totalling $791 all due to laptop's warranty period expired. Warranty renewal ($238 for 2 years NBD) was the reason I brought laptop to service center. For some strange reason, if you transfer your warranty outside of USA, you can no longer see expiration date on Dell.com and cannot get technical assistance but only do so through Dell branch in country you transferred warranty to.

Frankly, I did not expect it to be that high because my previous repair of 5 year old HP laptop would cost only $285 but the difference this time might be that laptop is considered business laptop, plus it is still new. So after I took it back from lab, good thing I disassembled it because I found out that 2GB of RAM memory module is missing but just to think about person who does not have technical skills for this... I don't know how it is in USA but in this lab and HP authorized lab, they never require you to specify the content of laptop i.e RAM modules, Wi-Fi adapter, DVD drive etc. and due to lack of such document, they can easily steal or avoid responsibility. This has got to change.

Funny thing is, for half of this price I could get used E6420 (except with only Intel integrated video card compared to mine) in great condition with 3 years warranty from eBay. And you know what? This E6420 laptop that I have has been brought by other person from US to my country 2 years ago, whom I paid $850 for it and condition was like new.

The boards have different part numbers: 054GVM and 0H2YDF. Many times people and Dell's techs told me to match my motherboard number to replacement motherboard.

Are you in shipment forwarding business? Or you just offer to individually pickup shipment and forward it to destination?

Can you clarify what is dual channel LVDS? Mine has 2 cords, one with big plug and the other with small plug. Does that make it dual channel? Is dual channel for integrated and discrete GPUs?

 

Well, we have our own service issues and politics here in the USA, but they are not as bad as your story and each state in our nation has additional laws in addition to our federal laws. Overall, the consumer is protected here.

Yes, my business is international and technology focused. I have forwarded packages to your country, throughout the EU, and numerous others within the region. There are a few members in these forums who I have assisted with Dell in the past since
I have also tested, reviewed, and dissembled just about all the latitude systems in that series. At any rate. you can PM me here or via email and we can talk if you need anything.

The LVDS (low voltage digital single) cable is your display interconnect cable. The 40pin connector is the data and voltage lines (plus the little LED board for when the screen backing is closed - see below). The little connector is a USB bus line for the webcam module above the LCD panel. The dual channel data lines (extra red wires) are needed for LED backlit displays that produce video at or in excess of 900p. Lower resolution displays like the common 720p cheapies are single channel and typically use cheaper cables without the extra wires.

Below are some pics of a 6420 I documented a year or so ago.

Scott