Acer V3-571 confounding diagnosis

[Larry Sabo]

I’m at a loss to explain the behavior of this Acer, which came in with a busted screen. Replaced the screen and the laptop refuses to power on. Disconnect the screen and it boots up and has video on an external monitor. Voltage at the DC entry point on motherboard goes to zero as soon as the video cable is plugged into the back of the screen, but not if the video cable is connected at the motherboard with the other end disconnected. Shorted screen, right? RMA it and get another new one: no change???

I’m at a loss to explain how this could happen (unless both new screens were shorted) and wonder if anyone has seen it before. A cross connection between 5v and ground within the video cable would explain it, not a 5V to a ground short within the cable. The screen supplier has confirmed that they tested the returned screen and it is not shorted. I am having trouble sourcing a replacement cable and motherboard and am on the verge of shipping the whole thing to Acer for out-of-warranty repair. However, I hate to give up and need to understand how this could happen.

Anyone else encounters such a problem?

 

[Kitten Kong]

Battery removed when swapping screens?

Cables are available here in the UK larry. If your stuck mate, let me know, I will order it for you, and send it over.

Same with mobo's. Available, costing around £90 or so.

 

[HCHTech]

If you put the original screen back in, does it also refuse to boot? This would take the new screens out of the equation at least. If it boots fine with the old screen, then the new screens have to be at fault. If not, then it's likely the cable or the motherboard.

 

[Larry Sabo]

@Nige: Thanks, buddy! I've inquired of Acer's authorized Canadian parts supplier and should hear back tomorrow. If no joy, I'll be in touch. Yes, the battery was removed before removing/installing the screens, as always. One only does that once, and that's history.

@HCHTech: Yes, the original screen displays the same symptoms.

I should have added that the customer's daughter busted the screen by accidentally kneeling on the laptop while it was on a bed, I was told. The lid is not damaged/deformed at all, nor the bottom cover, and I didn't see any obvious damage to the motherboard. If the damage to the screen had the same effect as disconnecting a screen without removing the battery, I would expect the LVDS supply fuse to be open circuit, which means connecting/disconnecting the screen connector should do nothing. It's also not the video camera, which was plugged in during all tests, even when the screen connector was removed. I could imaging an inverted video connector but the LVDS and screen connectors are polarized and can't be inserted upside-down. I am puzzled.

 

[Larry Sabo]

Just to bring this to a close, a new cable solved the problem. The original screen connector (shown below) was damaged, probably when I removed it. The damage and pins were so tiny, I didn't notice it. The plastic that supports the pins was also broken away at another spot; I suspect it was brittle from age.

 

[Kitten Kong]

Good to hear you finally got this sorted Larry.

Chalk another one up for the good guys.