HDX18 Screen Goes Black after Several Seconds of Lighted Display (HDX18t-1200) (679 Views)
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Flute-for-Fun
Posts: 19
Member Since: ‎06-08-2013
Message 1 of 10 (679 Views)

HDX18 Screen Goes Black after Several Seconds of Lighted Display (HDX18t-1200)

[ Edited ]

I've got an HDX18 with a screen that's going black, and I recognize there are several possible causes and am hoping that the specifics might narrow down the underlying cause.  (Model  HDX18t-1200)

 

1.  Upon boot the screen successfully displays the HP logo -- fully lit.

 

2.  There is some horizontal flicker that begins.  Before going black a very few horizontal 'white' lines appear, just as the whole display starts to go black.  Once black the display tends to stay black until restart of the laptop.

 

3.  Several seconds of lighted display usually elapse before going black.   It's sometimes possible to make it all the way to Windows user login, but more frequently screen blacks before that.   Or I can usually get to the advanced boot options menu where the screen will go black after a couple seconds sitting static at the menu display.

 

4.  I tried the "bright flashlight" test and discovered that the screen image IS FAINTLY PRESENT.  (Wow, with most other laptops I've been able to see the faint image without a flashlight...)

 

5.  I'm running an external monitor and the external monitor is working correctly.

 

6.  My experience so far has been that shutdown / restart will do the same thing --- i.e. the correctly lit display comes back for a few seconds before the display blacks.

 

 

I've read past forum discussions and got the notion that inverter, bulbs, and cable are all possibilities...

 

Are the few seconds of LIGHTED display helpful to narrow in on the most probable culprit?

 

 

 

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Huffer
Posts: 10,501
Member Since: ‎11-12-2008
Message 2 of 10 (664 Views)

Re: HDX18t -1200 Display Goes Black after Several Seconds of Lighted Display

That is an odd symptom. I would say it rules out the cable, but it still could be the inverter or the backlight bulb. If it were the cable you would not get any image ever. I would start with the inverter. They are inexpensive and easy. If that does not do it, I would replace the screen panel. The cost of screens has come down so much it does not really make sense to try and replace just the backlight.

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Flute-for-Fun
Posts: 19
Member Since: ‎06-08-2013
Message 3 of 10 (652 Views)

Re: HDX18t -1200 Display Goes Black after Several Seconds of Lighted Display

I do wonder if a failing backlight bulb or two bulbs could, or would characeristically, light temporarily and then go dark after a few seconds of operating?   I'm accustomed to "binary" bulb failures of course --- which light or don't light  --- but since I don't know a great deal about backlight bulb technology I realize I could make incorrect inferences from those other experiences.

 

Mulling this over now, I probably *will* start with inverter unless someone here adds to the discussion with an even more definitive/absolute answer.

 

 

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Flute-for-Fun
Posts: 19
Member Since: ‎06-08-2013
Message 4 of 10 (646 Views)

Re: HDX18t -1200 Display Goes Black after Several Seconds of Lighted Display

[ Edited ]

As one further description of symptoms, there was a round of flickering for a good 30 seconds or more and some of the flickers showed top half the screen, or showed top half the screen and then extended to show the entire screen area.  Screen stayed lit for a little while (several hours) and then went black and is back to a few seconds of lighted display per boot/wake.

 

I considered that one possible difference behind the "improved" behavior was lower ambient temperature and/or humidity.  Still thinking inverter as the first part to replace.  I haven't ordered the part yet because I've been holding to see if there are more replies on this thread.

 

 

 

Regents Professor
AttackofZaq
Posts: 4,472
Member Since: ‎10-09-2012
Message 5 of 10 (623 Views)

Re: HDX18t -1200 Display Goes Black after Several Seconds of Lighted Display

I agree with Huffer's suggestion.  I'd replace the invertor first and if that doesn't work I'd look into replacing the screen itself.

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Flute-for-Fun
Posts: 19
Member Since: ‎06-08-2013
Message 6 of 10 (618 Views)

Re: HDX18t -1200 Display Goes Black after Several Seconds of Lighted Display

Thank you.  I've got an inverter on order now and am interested to see where it leads.  

Regents Professor
AttackofZaq
Posts: 4,472
Member Since: ‎10-09-2012
Message 7 of 10 (602 Views)

Re: HDX18 Screen Goes Black after Several Seconds of Lighted Display (HDX18t-1200)

Hello again Flute-for-Fun!

Since you're going to be repairing this notebook yourself I wanted to make sure you took a look at your notebook's Maintenance and Service Guide.  This document will be invaluable when repairing the notebook.

Have a great weekend!

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Ozzuneoj
Posts: 4
Member Since: ‎08-24-2013
Message 8 of 10 (540 Views)

Re: HDX18 Screen Goes Black after Several Seconds of Lighted Display (HDX18t-1200)

My wife's HDX18t 1200 is having this exact same problem. Her system has had the widespread "touch buttons do whatever they want" problem for a couple of years now. I've attempted some of the fixes online, adding foil tape in certain places beneath the button panel, but nothing seems to have fixed these issues. She's had to use a USB wifi adapter and run the computer with the Media Smart software removed to limit the annoyance of the buttons.

 

A couple weeks ago though, her backlight seemingly died, and it would only work for a few seconds when the computer first turned on. I immediately thought "inverter!" and I tested it. I have an O-scope, and theres a trick where you simply set the o-scope to a range that only an inverter would put out, and set the leads near where the inverter is (without having to crack anything open). Sure enough, it would spike up when the screen was lit, then die when the screen went blank... one way or another, the inverter was shutting off. At this point I had seen the black horizontal sections of the screen flash at times and thought it was unrelated... I've seen other computers exhibit strange visual glitches while Windows starts, and I'd never thought anything of it.

 

So, I bought a replacement, which was rather expensive for an inverter ($15).

 

It was a pretty big pain in the butt getting into this laptop the first time to replace the inverter (while prying, I severed the HP logo wires inside the bottom of the screen and had to resolder new wires in... UGH!), but it turned out to NOT be the problem, because it was still having the same issues. So, I experimented some more. Moving the screen back and forth or turning the system on with the screen at different angles seemed to effect the backlight working, so I figured it was a bad LVDS video cable. I jiggled the cable several different ways and wasn't 100% convinced since no specific part of it seemed to cause the problem, but it was the only thing that made sense.

 

After plunking down another $22 for a new cable and installing it, I was immedately greeted by this problem AGAIN on the FIRST boot. After putting the system in standby (with it still rather loosely put together... some panels not attached) and turning it back on, the black horizontal portions of the screen was more clearly part of the problem. Tapping in various places would cause the black portions to appear. Tilting the screen back and forth rapidly would do the same. Then after a while, it just stopped doing this all together. It went away completely. I was getting pretty worried at this point.

 

I messed with it some more and it only briefly flashed a black section when I tilted the screen back and forth very quickly. Aside from this it was fine. I was getting very suspicious that this is yet ANOTHER symptom of the inexplicable button problem (most certainly related to static or grounding), so I took the computer to the power brick and plugged it in. Within seconds, the screen turned off and was back to its old ways.

 

What on earth did they do when they engineered these things? I've been building and repairing desktops for 13 years, and done a fair amount of work on laptops, and this is the first system I've seen with SO many strange electrical issues. And its one of the most expensive computers I've ever laid my hands on to boot...

 

I'm really at a loss here. My next step is to just start unplugging things and see what could possibly be causing the problem. It can't be the whole computer. Its extremely common on these systems, yet its something I've never seen on another computer EVER, so it has to be one specific component.

 

Any ideas are much welcome. My wife and I are going to be having our first baby in less than a month, and I'd really like to have her computer working so she can get the things done that she needs to do.

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RLough
Posts: 1
Member Since: ‎02-11-2014
Message 9 of 10 (310 Views)

Re: HDX18 Screen Goes Black after Several Seconds of Lighted Display (HDX18t-1200)

This is neither the screen or the screens power supply!  This is a firmware clitch...  That HP can not fix (apparently).

 

Close your lid, with the laptop on, and watch as you reopen and you will see the screen come back to life.  Sometimes only seconds, other times will last a minute (though rarely that long).  All the other functions related to the lid switch work fine, so the problem is not the switch.  HP needs to put out a firmware update to correct the error in the Screen Sleep timer.  This problem has existed for many years...   but HP has yet to fix it.  No hope in site.   :smileysad:

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Flute-for-Fun
Posts: 19
Member Since: ‎06-08-2013
Message 10 of 10 (305 Views)

Re: HDX18 Screen Goes Black after Several Seconds of Lighted Display (HDX18t-1200)

Somewhere else, I guess on another thread, I posted the results of how I repaired my HDX-18t....  I don't see it here so briefly here's how mine went:

 

I first tried replacing the inverter with no change in the problem.  

 

As another diagnostic, which I picked up from these discussion boards, I shone a very bright light at the screen (with laptop booted up) and images were still faintly discernable so I believed the data cable was unlikely to be the point of failure.

 

I considered trying to replace backlight bulbs only without replacing the rest of the screen.  I read several comments about how difficult a task that can be.  For my own part I heeded the warnings and concluded that frugality to replacing the bulbs alone would be strongly offset by the labor/difficulty involved in that approach.   I shopped and found a dual-bulb screen with proper specs, claiming to be first-quality, at a discounted price.  I needed to use a hot air source to separate the screen from its frame and I'd describe the job as a little fiddly but I replaced the entire screen and it's working fine today.

 

As for the touch-buttons, I tried all kinds of software updates etc. with the only result being a waste of my time.  Some of the suggested cures made little sense.  Finallly I found some instructions and video by a contributor named Haggis Cat and implemented the fix he suggested --- essentially beefing up some shielding along the cable pathways for the touch sensor.  That intervention worked beautifully for about a year after which I had to open again and update my fix probably owning to aging adhesive on the tape I used.  After another six months I'm starting to see some intermittent activation so I might have to use new material.  I've gotten 1 1/2 years of service with Haggis Cat's fix (and I suppose that my materials and workmanship probably were not quite as good as his).  

 

It's disappointing that I've had to experience all the trouble with the HDX 18.  I've had less trouble experiences with another workhorse brand.  But at least I'm thankful that I've been able to continue the service-life of the unit.

 

 

 

 

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