Video, but no video - huh????

[texson]

This is really perplexing and I am hoping someone here can shed some light on this problem -

I have an HP DV7 that was brought to me DOA. Nothing. Would not turn on, no fan spinning, lights...nothing. I did a reflow but to no avail so I turned to ebay and bought a board from a working machine - complete with CPU. Got the board in, connected it and got a display on the LCD. Assembled the machine, turned it on and - NOTHING. SSSoooo, I did a reflow on THIS board, reconnected it and now I get video on the external monitor but nothing on the LCD. Checked with a flashlight and there is nothing being displayed on the screen. I switched to another DV7 case and same thing - video on the external only.

I have never seen this before. Normally, if you get video on the external, you will get it on the LCD. Is it possible that the circuitry to the internal video output is bad? The answer would be 'obviously', but I don't readily buy in to that either so I am stumped.

Other info - the board is not completely installed - just laying on the bottom case with the internal video, power switch and hard drive connected.

Anyone every run across this situation before? Anyone have any suggestions?

Thanks for taking the time to read this post.

 

[Mainstay]

I wouldn't even remove the screws on the bottom of a dv7... let alone order a replacement board, let alone do any of that fancy reflowing.

An HP dv7 goes in the bin. And I even begrudge the time spent to properly recycle them.

Any grounding issues on the video power inverter?

 

[Larry Sabo]

In some designs, the GPU provides the LVDS video while the Northbridge provides the VGA video. A bad GPU can result in what you are seeing.

 

[Krynn72]

Mainstay is right, all the DV# laptops are garbage at this point. You're probably still having a gpu issue, and you can reflow it to your heart's content, and maybe you'll even revive it! Then next week your customer will be back saying you never fixed the issue and complaining how you didn't even test it and blah blah blah. Maybe you'll then decide to replace the motherboard entirely, only to find out that the "new" motherboard you bought from some chump online has been reflowed itself and dies on the customer in 2 days.

Display issues on a HP DVwhatever is data recovery only for us. 100% not worth even the smallest effort.

EDIT: Whoops, I reread your post and realized I missed the bit where you already bought a bunk motherboard online lol. Properly functioning motherboards for DVs online are pretty much non-existent.

 

[frase]

DV7 cannot stand them worst designed laptop ever

 

[Ktex]

Older dv7s had a CCFL screen, are you sure no video output? There might not be a signal (EN) for the inverter to turn on the lamp. An external inverter for turning on /checking the lamp comes handy.
Or if its an LED, there might still be no signal for the leds to turn on. Both indicate a bad motherboard.
On the reflow issue, I used to do it, until the real problem was explained to me. The chip MUST be replaced, it's not the balls, but the circuitry inside the fiberglass substrate of the graphics chip that pops up. That's why heating the chip to 120 C for five or so minutes will sometimes make it work. Try it, sometimes you don't even need to take out the motherboard, just protect the screen, keyboard and delicate plastics. Anyway, reflows are still no good, the chip is busted. Look for small half bubbles on top of the chip. It takes less time than a complete reflow, and will tell you for certain if it's the graphics chip.

Edit: frase, I think it's the dv6000 with nvidia chips that had the worst design.