Display power but no image, HP Pavilion DV-4 1465dx

My computer is a Pavilion DV-4 1465dx, which I purchased in the summer of 2009. I upgraded from Windows Vista to Windows 7 last fall. (About time!) The only hardware problem I had before this year was a corrupted hard drive, which I replaced over the 2012 summer. In late April 2013 however, I lost video in the LCD. This problem occurred without much warning, aside from a slight display flicker once when closing the laptop, perhaps the last time the screen worked properly. There had been other indications of hardware issues – the webcam would only work at certain screen angles – which led me to believe there was a faulty connection in the display cable.

To provide more information on the problem itself, the screen powers on but shows no image, just a uniform grey appearance. I can vary the screen’s brightness by both software and hardware input, but I have no image itself. The computer appears to function completely normally everywhere else – it still boots normally, still recognizes the display, operates normally, and outputs perfect video when connected to an external monitor.

I searched online for potential solutions and found that these models often had trouble with the display cable. This seemed to match my symptoms of screen power but no signal, and spotty webcam connections. If I understood correctly, the performance also ruled out problems with the inverter (the little circuit board at the bottom of the screen) because the screen still had power and brightness control. I purchased a new cable (and a new LCD, as I had cracked the old one in haste to remove the screen bezel, not my best moment) and when they arrived, I connected and reassembled everything on my laptop, and powered it on. Nothing had changed. The same exact performance and issues were present. Confounded, I tested both cables, pin for pin, with a multimeter, only to find that one of the connections for the original cable *was* broken, and that the replacement cable was intact. (I drew diagrams of the wiring as I tested, and I can post these if seeing them would help?) I had fixed the cable, but had not restored display functionality, which meant that somewhere else in the system there must be a broken circuit.

This is where I need help! The laptop is no better, and no worse. Further searches online suggested that there might be a broken solder on the display chip’s BGA (ball grid array) connection to the motherboard, which can only be repaired by heating and “reflowing” that area of the board. However, I understand that this is a potentially risky procedure due to heat-sensitive motherboard elements (capacitors). Additionally, I believe that if there are connection issues on the motherboard, I would see some combination of flashing Caps Lock and Num Lock lights? This has not been observed.

I purchased a new computer (a Surface Pro) this summer, but I still anticipate using this laptop in some situations, if possible. Is there anything else I can try, short of cooking the processor with a heat gun? Any diagnostics I can run that might shed more light on this situation?

 

I have some experience with these notebooks ( see here) and have disassembled ours several times without issue. Relatively speaking it is one of the easier notebooks to disassemble. I replaced the same ribbon cable you speak of due to intermittent horizontal lines on the screen based on screen position. Though I guess the BGA issue could be your problem, I've not heard of it as a common problem with these notebooks. As far as I know it was only the Nvidia 8400GS and related era models that had the BGA issue and only specific models of those.

At-any-rate, my first thoughts are inverter, inverter wiring, display, or ground. The display and ribbon cable would be last on my list since you just replaced them both. That leaves inverter and/or wiring/connections. My suggestions would be to get a new inverter (it's getting pretty old anyway) and go back and check your work. If you need to, completely disassemble the unit and trace all the cross-over wiring... display to base. Webcam, microphones, WiFi antennas, inverter, and display. Look for worn insulation and use your voltmeter again to check continuity.

If you're uncomfortable with the total disassembly, there are a couple of very good how-to videos for this unit on YouTube. Hope that helps!

Best, Dave

 

Thanks for the feedback, Dave.

Would a broken inverter be capable of producing the symptoms I'm seeing? As in, power to the display but no image? If I understand correctly, the inverter simply provides power to the screen, since only two wires run from the inverter to the LCD, and display power does not seem to be the issue. But maybe a bad inverter could keep the screen from displaying any images? I don't know.

When I traced the wiring for the display cable, I also traced the wiring for everything else that connected to that plug - the webcam, inverter, and light-up HP badge. For both the old and new cables, there did not seem to be any missing or broken connections for the inverter wires, so I think that can be ruled out as well.

Are there any other failure points you could think of, and ways to test them? Thanks!

 

My knowledge is a bit limited here, but I believe (electronically speaking), the inverter powers the LCD screen and the backlight. This is why when trouble shooting a bad inverter, you can usually only view the display on an external monitor. If the screen were just black then I'd say shine a flashlight into a dark screen. If you could see an image, this would indicate that the inverter were good but that the LCD backlight failed.

The most logical point (to me) is the inverter connections (pins) and all associated wiring. If that ain’t it, then the next most likely issue is the inverter itself provided that your new LCD is good. The puzzling thing is that you have a gray screen with brightness control. Do the wifi, mics and webcam work? Inverter, wiring, LCD are about the only physical aspects but without being an expert with specific component test equipment, the only way I know is to triple check the wiring and try replacing one or the other parts (LCD or inverter). As a long shot have your tried reinstalling/updating the chipset and/or video drivers while attached to an external display. You might go to Intel and try that.

KLF, 2.0… where are you guys? They are usually pretty good with this kind of stuff. Sorry I couldn’t have been more help. /Dave

PS... the part number on my invertor was/is PK0700008J00-A00-8BH-08664. I think they differ slightly from unit to unit but you can get a new one here. I think if you give them your part number they will confirm compatibility.