zombie laptop screen

June 1, 2007 2:03 PM

Is my laptop experiencing organ transplant rejection?

I have a HP Pavilion laptop (DV1310us, almost 2 years old, far past warranty) whose screen went very dim a couple weeks ago, though I can make out images if I shine a flashlight at the screen. Lots of research pointed at the problem being with the LCD inverter, so I ordered one. But the new inverter I got is slightly different from the old one - it seems HP used a few different LCD inverters throughout the dv1000 series, and I received the other model. I replaced the old inverter anyway, and now this is what happens:

- if I boot up the laptop on battery power only, the screen is bright for a second on startup and then goes dim again. Closing and reopening the lid has the same effect.

- if I boot up the laptop with the AC cable plugged in, everything works, even if I remove the plug later, and the screen remains bright. Yay!

Is it possible that the new inverter is working perfectly, and there's some other issue with the battery instead?
(for reference - old inverter: AS023172018, new inverter: AS023172140)

posted by casarkos to technology (6 comments total)

The fluorescent lamps in LCD backlights require a high "strike" voltage on powerup, and then lower voltages to keep operating. My guess is the battery is not able to provide enough power at the beginning, while the AC cable can. However, the battery is sufficient to produce the normal operating voltage after you power up using the cable.
posted by Krrrlson at 3:07 PM on June 1, 2007

(Note that this is not necessarily the battery's fault. Since your inverter is a different model, it may be intended for use with a different series of batteries.)
posted by Krrrlson at 3:09 PM on June 1, 2007

Should have included in the original question: and is there anything I can do about this (other than trying to find and order an old-model inverter)?
posted by casarkos at 4:40 PM on June 1, 2007

When this same thing (LCD is working correctly but not being correctly illuminated) happened to my Dell laptop, it wasn't a power supply issue but the lamps themselves -- the lamps had burned out. Between perfect-working and no-working, I had a several-week period where the LCD would work (be fully lit) intermittently or would seem to respond to power changes, but not as consistently as you're describing. I thought this was worth mentioning in case.
posted by sparrows at 11:22 PM on June 1, 2007

Given some circuits experience and testing equipment, probably. Will it be easier or cheaper than buying a new inverter or battery? Probably not.

You could try looking up the specs for your battery and inverter, and seeing if the inverter is exceeding the battery's current rating - I wasn't able to locate the specs for the inverter models you mentioned with basic Googling, maybe you can do better.

You could also try to replace the inverter and/or the battery. However, it would be nice to sit down with a multimeter and scope and check if the problem is indeed what I think it is before you waste more money. There is also a possibility that something else is causing the problem -- for instance, some short or leakage path (that might have killed your original inverter in the first place) that is draining power and preventing the inverter from getting enough juice.

If you can deal with having to use the AC cord to start up every time, that's the easiest thing to do. If you have a spare hundred bucks lying around, you could risk it and try buying the correct inverter, though, again, there are no guarantees. If you want to examine the innards of the laptop for kicks, check for burn marks or blown capacitors.

I think that's pretty much all I can say without looking at the thing myself.
posted by Krrrlson at 11:46 PM on June 1, 2007

And yeah, I was going on the assumption that the bulb was working fine -- if there's symptoms similar to what sparrows described, that's another avenue to explore.
posted by Krrrlson at 11:48 PM on June 1, 2007